Infectious Disease

Question 1

A 9-year-old presents with a history of travel to the Rocky Mountains for a camping trip this summer. He has had watery, smelly diarrhea for the last week with multiple episodes daily of flatulence. His mother says that he has been burping a lot and that it smells horrible, “like sulfur.”

What is the most likely diagnosis?

Answer 1

Giardiasis

Giardia is the most common disease-causing parasite in the U.S. It also is the most frequently identified diarrheal agent in waterborne-associated infections. Acute symptoms are like those described here (“sulfuric belching” is common). Diagnose by checking for a Giardia-specific antigen in the stool.

Question 2

A mother develops chickenpox in the perinatal period.

What time frame determines which newborns should be given varicella immunoglobulin (VZIG)?

Answer 2

Mother Had Varicella 5 Days Before to 2 Days After Delivery

This is very important to remember! These infants are at high risk for severe varicella infection! In this time frame, the newborns get exposed to the virus from the mom but have no protective antibody passed to them.

Question 3

A 4-year-old boy presents with:

• Fever
• Vesicles on his buccal mucosa
• Vesicles on his tongue
• Red maculopapular rash on his hands and feet

What is the most likely etiology of his signs and symptoms?

Answer 3

Coxsackievirus

Coxsackievirus is commonly the cause of hand-foot-and-mouth disease (especially coxsackievirus A16). In infants, the diaper area is commonly involved with the rash. In addition to coxsackievirus, enterovirus Type 71 (EV-71) can cause this.

Question 4

A 7-year-old girl comes into your office to get her flu vaccine but is allergic to eggs.

Can you still give her a flu vaccine, or do you have to refer her to an allergist?

Answer 4

You can still give her a flu vaccine.

The inactivated trivalent and quadrivalent influenza vaccine (IIV) is produced in eggs, but data have shown that IIV can be safely given to people with egg allergy. According to the Joint Task Force on Practice Parameters (representing the American Academy of Allergy, Asthma, and Immunology and the American College of Allergy, Asthma, and Immunology), the special precautions regarding medical setting and waiting periods after the administration of IIV to egg-allergic recipients beyond those recommended for any vaccine (i.e., 15 minutes so as to avoid hurting themselves if they faint) are no longer warranted.

Question 5

A 13-year-old girl has a staple injury (clean, minor wound). She has had 7 immunizations for tetanus, and her last immunization was 7 years ago.

What do you recommend for her as far as immunization for tetanus?

Answer 5

No Immunization

If the patient has had ≥ 3 immunizations in the past, and it has been < 10 years since her last immunization, then she does not require further tetanus immunization.

Question 6

Two children, 9 months and 3 years of age, neither of whom have received MMR, present for evaluation 24 hours after a community-wide outbreak of measles affecting infants and children of all ages was identified.

Is postexposure prophylaxis with MMR indicated in neither, one, or both of the children?

Answer 6

Both

During a community-wide outbreak of measles, measles vaccine given within 72 hours of exposure to susceptible individuals provides protection or disease modification in most cases. Measles vaccine should be considered in all exposed individuals who are eligible to receive the vaccine (> 12 months of age) and who have not been vaccinated or have received only 1 dose of vaccine. In addition, MMR vaccine may be administered to infants 6–11 months of age. However, seroconversion rates after MMR immunization are significantly lower in children immunized prior to 12 months. Therefore, any dose received prior to 12 months should not count toward the recommended 2-dose series.

Question 7

A patient in the summertime from rural Connecticut presents with:

• Fever
• Headache
• Leukopenia
• Thrombocytopenia
• Anemia
• Elevated AST/ALT

What is the most likely diagnosis?

Answer 7

Anaplasmosis

Human granulocytic anaplasmosis (HGA, due to Anaplasma phagocytophilum) is a tick-borne disease that predominates in the Northeast and Midwest. Classically it presents with a pancytopenia and fever. A similar disease, human monocytic ehrlichiosis (HME, caused by Ehrlichia chaffeensis), occurs in Arkansas, Missouri, and Oklahoma.

Question 8

A 2-year-old day care attendee presents with:

• Fever
• Vomiting
• Bloody diarrhea
• New tonic-clonic seizure
• WBC is elevated with a significant bandemia.
• Rectal prolapse

What is the most likely etiology for the diarrhea and the other findings?

Answer 8

Shigella

Shigella is a common cause of diarrhea, especially in day care centers. Children 1–4 years of age have the highest incidence. Bloody diarrhea and seizures commonly occur. Rectal prolapse occurs in 5–8%. Bandemia is also very common. Most illnesses are self-limited, but antibiotics are recommended in severe cases and can shorten the disease course and limit its spread to others. Treat with Ceftriaxone or a macrolide.

Question 9

Amphotericin B causes renal losses of which 2 electrolytes?

Answer 9

Potassium and Magnesium

Amphotericin B is a polyene antifungal agent. While amphotericin B remains an effective treatment for most systemic mycoses, it has many side effects. These include fever, renal failure, phlebitis, and acidosis, as well as low potassium and magnesium. Always monitor serum potassium and magnesium levels during amphotericin B therapy.

Question 10

A 12-year-old boy who lives in Arizona loves to hunt prairie dogs and skins them with his old hunting knife. He presents with a 3-day history of fever; chills; headache; and a painful, swollen right inguinal lymph node.

What organism do you suspect?

Answer 10

Yersinia pestis

Y. pestis causes plague. The reservoir is wild rodents. Infection is transmitted by fleas or by direct contact such as through skinning animals. It has a high mortality. The bubonic form of plague causes painful swollen lymph nodes (buboes). If not treated, it can lead to the septicemic form, characterized by hypotension, respiratory distress, organ failure, and death. The bubonic type also can lead to a pneumonic form (bioterrorism related). Most human cases occur in New Mexico, Arizona, California, or Colorado.

Question 11

A newborn of a mother who recently immigrated from Albania presents at birth with:

• Petechiae and purpura on the face, trunk, and extremities
• Hepatosplenomegaly
• Hemolytic anemia
• Patent ductus arteriosus (PDA) without pulmonary artery stenosis
• Cataracts with microphthalmia
• Radiolucencies in the metaphyseal long bones

What is the most likely diagnosis?

Answer 11

Congenital Rubella Syndrome

Rubella was eliminated from the U.S. by 2004. By 2015 it was eliminated from the Americas. Today, < 10 people in the U.S. are reported as having rubella each year. Since 2012, all rubella cases had evidence that they were infected while outside the U.S. It continues to be endemic in many areas of the world.

This infant has petechiae and purpura consistent with the “blueberry muffin” baby as seen in CMV, but she also has a PDA and cataracts, which are classically seen in congenital rubella syndrome. Most likely, the mother was infected in the 1^st trimester.

Question 12

An infant is suspected of neonatal sepsis and started on ampicillin and gentamicin.

Which of these medications requires dose adjustment because of age-related factors in renal function?

Answer 12

Gentamicin

Gentamicin is an aminoglycoside. Dosing differs in neonates and young infants because of immaturity in renal function (decreased glomerular filtration rate and larger total body water composition as compared to older children and adults). The kidneys are one of the primary routes of drug excretion, along with the liver.

Question 13

A 17-year-old presents with:

• Pneumonia
• Diarrhea
• CNS symptoms (headache, delirium, and confusion)

What is the most likely etiology of this triad?

Answer 13

Legionella pneumophila

L. pneumophila causes 80–90% of human Legionellae infections. L. pneumophila infection (legionellosis) is a multisysytem disease, with the 3 findings listed here being the classic triad. It is commonly associated with outbreaks related to contaminated water towers or air-conditioning water units in buildings, hotels, cruise ships, and hospitals. Legionellae infections are rarely seen in children.

Question 14

A newborn presents with:

• Microcephaly
• Hydrocephalus
• Hepatosplenomegaly
• Maculopapular rash
• Retinochoroiditis
• Cerebral calcifications (widespread)

What is the most likely diagnosis?

Answer 14

Congenital Toxoplasmosis

Toxoplasmosis during pregnancy can be very problematic. The risk to the fetus of congenital infection increases as the pregnancy progresses from 25% in the 1st trimester to 65% in the last trimester. However, the severity of disease is inverse to this: infants infected early in pregnancy are more likely to be severely affected, like the child in this scenario.

Remember: if calcifications “CircuMVent” the ventricles (i.e., are periventricular), the cause is almost always CMV, not toxoplasmosis!

Question 15

A 15-year-old boy who lives and works on a sheep farm presents with a painless papule that vesiculates and forms a painless ulcer, then a painless black eschar with nonpitting, painless induration and swelling.

What is the likely diagnosis?

Answer 15

Anthrax

Anthrax inoculation occurs from handling contaminated hides/wool. It can progress to septicemia and meningoencephalitis if left untreated. The cutaneous form (95% of cases) presents as described. Associated symptoms can include fever, headache, and painful lymphadenopathy.

Question 16

An unimmunized child presents with buccal cellulitis (full thickness palpable on both sides of the cheek and purplish in color) due to Haemophilus influenzae.

What do you expect to find systemically?

Answer 16

Bacteremia

Patients with buccal cellulitis due to Haemophilus influenzae are almost always bacteremic. These children should always be admitted and placed on IV antibiotics.

Question 17

You have diagnosed a patient with active tuberculosis.

What comorbid conditions should you consider before prescribing isoniazid as part of your treatment regimen?

Answer 17

Acute Liver Disease (of Any Etiology) and Alcohol Use

Isoniazid (a.k.a. isonicotinic acid hydrazide [INH]) is metabolized in the liver. It induces components of the cytochrome P-450 system when combined with alcohol, thus increasing toxicity, and is contraindicated in patients with acute liver disease. In all patients on INH, regardless of age, monitor monthly for signs and symptoms of liver toxicity. Laboratory testing is indicated if signs or symptoms develop. INH carries an FDA boxed warning regarding the risk of hepatitis.

Question 18

You are on a medical mission trip in Uganda and are visiting a new mother infected with HIV.

Do you recommend that she breastfeed her infant?

Answer 18

Yes

In developing countries that have limited resources, the WHO continues to recommend breastfeeding even for the HIV-infected mother for the 1^st year of her infant’s life. In developed nations, such as the U.S., where formula is readily available, breastfeeding is not recommended because it is a means of HIV transmission.

Question 19

A 4-day-old infant presents with bloody, green discharge from the eyes. He was born at home.

What is the most likely diagnosis?

Answer 19

Gonococcal Ophthalmia

Gonococcal ophthalmia presents 2–7 days after delivery with bloody, green, or serosanguineous discharge from the eyes. Gram stain the discharge and culture for N. gonorrhoeae.

Question 20

A girl presents with chickenpox.

When are patients with chickenpox contagious?

Answer 20

1–2 Days Prior to Onset of the Rash

Until All Lesions Are Crusted Over

Children may return to school or day care when the lesions are crusted over. Hospitalized patients who are exposed need to be placed in a negative-pressure isolation room if their hospitalization falls within the timeframe of days 8−21 after exposure.

Question 21

Who is at greater risk to develop neuroinvasive disease from West Nile virus (WNV)—a healthy 10-year-old girl or her 65-year-old grandmother?

Answer 21

The Grandmother

The majority of infections with WNV are asymptomatic with approximately 20% of people developing a self-limited febrile flu-like illness. The risk of neuroinvasive illness increases with age and is highest among adults > 60 years of age.

Question 22

A 14-year-old boy presents with diarrhea. You learn that he has a pet iguana in the house.

What is the most likely cause of his diarrhea?

Answer 22

Non-typhoidal Salmonella

The main cause of Salmonella outbreaks is contaminated food, including frozen foods (especially chicken), milk, eggs, produce, and peanut butter; however, iguanas, baby chicks, frogs, turtles, and other exotic pets can also be sources of infection.

Question 23

A 15-year-old who lives on a farm and loves to eat chitterlings presents with an appendicitis-like syndrome.

What organism is most likely responsible if this is not appendicitis?

Answer 23

Yersinia pseudotuberculosis or Yersinia enterocolitica

• Y. pseudotuberculosis* or Y. enterocolitica can each cause pseudoappendicitis syndrome, especially in older children and adolescents. This presents clinically just like appendicitis, but at the time of surgery, the appendix appears normal with inflammation of the terminal ileum and mesenteric lymph nodes.
• Y. enterocolitica* is transmitted by ingestion or handling of raw or undercooked pork products (especially chitterlings, which are made from pig small intestines), contaminated water, or direct/indirect contact with animals.

Question 24

A 13-year-old girl steps on a dirty rusty nail. She has had 6 previous tetanus immunizations with her last being a DTaP immunization 6 years ago.

What do you recommend for her today?

Answer 24

Tdap Immunization

The girl has had ≥ 3 tetanus immunizations in the past, so she does not require immuneglobulin for this dirty wound. However, her last tetanus immunization was 6 years ago and was a DTaP. She has not had a Tdap booster that includes pertussis, so she needs this today. If her last immunization 6 years ago had been a Tdap, then today she would be given a Td. (Only 1 Tdap per lifetime at present.)

Question 25

A neonate with meningitis grows Citrobacter in her blood culture.

What is the next test you should order?

Answer 25

CT or MRI of the Head

You should be very concerned about a brain abscess; therefore, order a CT or MRI of the head. Brain abscesses occur in ~ 75% of Citrobacter meningitis cases.

Question 26

A college student presents with vomiting. He felt ill 1 hour after eating leftover fried rice (left overnight on the counter) this morning.

What is the likely diagnosis?

Answer 26

Bacillus cereus Toxin Food Poisoning

B. cereus is a close relative of B. anthracis. It can cause 2 forms of gastroenteritis:

1. A short-incubation (1–6 hours) emetic type, due to preformed heat-stable toxin
2. A longer-incubation (8–16 hours) diarrheal type, due to heat-labile enterotoxin production in vivo in the GI tract

This patient has the emetic form, which often results from consuming fried rice left at room temperature. This gastroenteritis is self-limited and only needs symptomatic treatment.

Question 27

A 10-year-old boy presents with:

• Severe sore throat
• Temp 102.0° F (38.9° C)
• Tender cervical lymphadenopathy
• Exudative tonsils
• Rhinorrhea

Which procedure should you perform: a rapid strep test, strep culture, both, or neither?

Answer 27

Neither

Presence of cough, rhinorrhea, or other symptoms of URI with sore throat is more suggestive of a viral etiology than streptococcal infection. Do not check for group A Streptococcus if URI symptoms are present. If he did not have rhinorrhea, then everything else fits for strep infection.

Question 28

A 5-year-old girl presents after a cat scratch with a 1-week history of a tender, left axillary lymph node. (The scratch was to her left hand.)

What is the name of the organism most likely responsible for her disease?

Answer 28

Bartonella henselae

This is cat scratch disease (CSD), which is caused by Bartonella henselae. Treatment is supportive, and the key is to not incise and drain the lymph node because a persistent sinus tract will likely develop. Azithromycin has been shown to reduce the time for lymph node swelling to resolve. However, spontaneous resolution usually occurs in 2–4 months without antibiotics.

Question 29

A 10-year-old boy from the Ukraine with no immunization history presents with:

• Sore throat
• Hoarseness
• Temperature 100.0° F (37.8° C)
• Conjunctivitis
• Gray-white pharyngeal membrane

What is the most likely diagnosis?

Answer 29

Diphtheria

Corynebacterium diphtheriae is the cause of diphtheria. Tonsillopharyngeal diphtheria is an upper respiratory infection with these findings (note the low fever). 10% of patients with diphtheria develop myocarditis, which typically occurs in the 1^st week of infection.

Question 30

A child has a persistent tooth abscess that has been ignored for several weeks. Now he presents with drainage on the outside skin lateral to the infection of his molar. Stains of the drainage show yellow “sulfur” granules.

What is the most likely diagnosis?

Answer 30

Actinomyces

Actinomyces is a microaerophilic/facultative anaerobic organism that is part of the oral and gastrointestinal flora. It can cause infections of normally sterile sites, presenting as described here. The characteristically yellow “sulfur” granules are actually clusters of organisms. Actinomyces is most commonly associated with dental infections, but it can also cause pelvic inflammatory disease (PID) in adolescents using IUDs.

Question 31

A 5-year-old presents for her first influenza vaccine.

How many should she receive?

Answer 31

2 Doses 1 Month Apart

For children < 9 years of age who have never been vaccinated, this vaccination schedule will produce adequate antibody levels. Thereafter, they receive 1 annual vaccine.

Question 32

A 17-year-old boy presents with submandibular swelling and fever. He is diagnosed with mumps.

Which genitourinary complication occurs commonly in mumps?

Answer 32

Epididymo-Orchitis

In postpubertal boys with mumps, 15–35% get epididymo-orchitis. Oophoritis occurs in ~ 7% of girls. Other significant complications of mumps include:

• Mastitis (described in 31% of adolescent girls in a 1956–1957 outbreak)
• Meningitis (common, but usually self-limited)
• Temporary deafness (in one study, 4% of those affected)

Question 33

A patient from North Carolina presents with:

• Fever
• Headache
• Arthralgias
• Maculopapular rash on the extremities that has become more petechial
• Serum sodium is 128 mg/dL.
• Platelet count is 110,000/µL.

What is the most likely diagnosis?

Answer 33

Rocky Mountain Spotted Fever (RMSF)

This is the classic scenario for RMSF, a tick-borne disease caused by Rickettsia rickettsii. It is mainly found in the mid-Atlantic states. The rash (which is absent in ~ 20% of patients) begins at the ankles and wrists and then spreads within hours to the trunk, palms, and soles, progressing from maculopapular to petechial to purpuric. This disease has a 3% mortality rate. Treat with doxycycline in all ages.

Question 34

A college freshman presents with:

• Cough
• Coryza
• Conjunctivitis
• Fever
• Malaise
• Splenomegaly
• Macular rash that began on the hairline and now has spread to the trunk

What is the most likely diagnosis?

Answer 34

Measles (Rubeola)

Measles is still occurring in scattered outbreaks around the U.S., particularly in colleges. The 3 Cs of cough, coryza (rhinitis), and conjunctivitis (with photophobia) are classic with the rash. Koplik spots (whitish spots on an erythematous base), which appear on the buccal mucosa 2–3 days before the rash appears, are pathognomonic. Splenomegaly and lymphadenopathy are also common. Negative pressure isolation room needed.

Question 35

A 3-year-old presents with:

• Fever
• “Slapped cheek” rash on the face
• A “lattice-like” rash on the arms and legs that is more prominent in sunlight or with a warm bath

What is the likely etiology of these signs and symptoms?

Answer 35

Parvovirus B19

Parvovirus B19 is responsible for this classic presentation of erythema infectiosum (fifth disease). Once the rash appears, the child is no longer infectious. Adults commonly get small joints arthritis (particularly of the hand).

Question 36

How does early-onset group B streptococcal infection present in the newborn?

Answer 36

Septicemia (45%) and Pneumonia (40%)

Early-onset group B Streptococcus (GBS) infections occur at 0–7 days of age. Obstetric complications and prematurity are commonly factors with early-onset GBS disease. Meningitis is rare (< 10%) in this age group.

Question 37

A 15-month-old girl received 1 dose of MMR at 10 months of age during a community-wide outbreak of measles.

Will this patient require 1 or 2 additional doses of MMR prior to 6 years of age?

Answer 37

2

MMR is routinely recommended at 12–15 months and 4–6 years of age. During a community-wide outbreak of measles, MMR vaccine may be administered to infants 6–11 months of age. However, because of the presence of maternal antibody, seroconversion rates after MMR immunization are significantly lower in children immunized prior to 12 months of age when compared to those immunized after 12 months. Therefore, doses received prior to the 1^st birthday should not count toward the recommended 2-dose series.

Question 38

A 2-year-old boy presents with enlarged, matted anterior cervical lymph nodes. When combined, they measure about 3 × 6 cm. The nodes are painless. A tuberculin skin test (TST) is performed and its diameter of induration is 8 mm. The nodes have been persistent for 2 months despite various courses of antimicrobials, including cephalexin and amoxicillin/clavulanate.

What is the best management at this time?

Answer 38

Complete Excision of the Nodes

This is lymphadenitis, most likely due to atypical mycobacteria, either M. scrofulaceum or M. avium complex (MAC). Treat by completely excising the nodes. Do not incise the node—it causes a chronic draining lesion. If not excised, most recede within 2 years.

Question 39

A 6-year-old girl who has been attending summer camp presents with:

• Fever
• Pharyngitis
• Conjunctivitis
• Rhinitis
• Cervical adenitis

What is the likely etiology for her signs and symptoms?

Answer 39

Adenovirus

Adenovirus can cause a pharyngoconjunctival fever, particularly during the summer months, and is commonly associated with outbreaks at swimming pools in summer camps. It can also cause epidemic keratoconjunctivitis. This occurs with conjunctivitis, painful corneal involvement, and preauricular lymph node enlargement.

Question 40

A 13-year old from Missouri presents with:

• Interstitial pneumonia
• Palate ulcers
• Splenomegaly

What is the most likely diagnosis?

Answer 40

Histoplasmosis

Histoplasmosis is endemic to the Mississippi and Ohio River valleys and is associated with bird and bat droppings. Remember that histoplasmosis has a pneumonia with splenomegaly similar to Chlamydophila psittaciinfection, but histoplasmosis commonly also has the palate ulcers.

Question 41

What is the most common cause of an IV catheter-related bacteremia?

Answer 41

Staphylococcus epidermidis

S. epidermidis is usually methicillin resistant. It is the most common cause of both catheter-related bacteremia and postoperative bacteremia, which occurs when foreign material is left in the body (e.g., prosthetics, including heart valves and joints; pacemakers; and most prominently, ventriculoperitoneal [VP] shunts).

Question 42

A child with cyanotic heart disease presents with new-onset headache and seizure. MRI shows a brain abscess.

What are the likely organisms?

Answer 42

Staphylococcus aureus

S. aureus infections of the CNS (e.g., meningitis) are unusual, but children with cyanotic congenital heart disease have an increased risk of staphylococcal brain abscesses, especially if there is endocarditis with septic emboli.

Question 43

A 15-year-old girl presents with:

• History of mild URI similar to a common cold
• Persistent (> 2 weeks) cough that causes her to cough for long periods of time
• No fever
• CBC is normal.

What is the likely diagnosis?

Answer 43

Pertussis

You may have been thinking pertussis until the CBC was reported as normal. In adolescents, the CBC usually is normal. An elevated WBC with an absolute lymphocytosis is generally only seen in infants and younger children, not in adolescents. This girl’s pertussis has advanced to the paroxysmal stage. Cough-variant asthma can present the same way.

Question 44

A family presents with a history of staying in a rural cabin in southern Colorado. It was summertime, and they had slept with the windows open to enjoy the fresh, cool night air. On awakening the next morning, they found a dead bat in the bedroom that they had been sleeping in.

What should happen next?

Answer 44

Give Rabies Immunoglobulin (RIG) and Vaccine

This is a classic “bat found dead in the room” exam question. Rabies virus is especially common in bats but is also found in dogs, cats, wolves, ferrets, raccoons, skunks, and foxes. On the exam (and in real life), give RIG and vaccine to anyone who was sleeping in the room, even if there is no evidence of a bite or scratch (except in rabies-free Hawaii).

Question 45

A child presents with bacteremia due to MRSA.

What is the antibiotic of choice?

Answer 45

IV Vancomycin

Newer agents are available, but for children, vancomycin remains the drug of choice for the treatment of MRSA bacteremia.

Question 46

A 17-year-old girl with HIV learns that she is pregnant. Her most recent CD4 count was 780 cells/µL and she has not been on anti-HIV medications. A repeat CD4 count is now 820 cells/µL.

Should she be started on anti-HIV medications?

Answer 46

Yes

Current HIV therapy guidelines list pregnancy as a “definite” for starting anti-HIV medications. The risk of infection for an infant born to an HIV-positive mother who did not receive interventions to prevent transmission ranges from 12–40% (average 21–25% in the U.S.). Programs designed for the prevention of mother-to-child transmission can reduce the rate of transmission to < 1%.

Question 47

A 15-year-old boy with IV drug use history presents with:

• Positive blood culture with viridans streptococci
• Fever
• Positive rheumatoid factor (+RF)

What is the most likely diagnosis?

Answer 47

Endocarditis

Using the modified Duke criteria, this boy has 1 of the 2 major criteria (positive blood culture with viridans streptococci) and 3 of the 5 minor criteria (IV drug use, fever, +RF) for a diagnosis of endocarditis. In this case, 1 Duke major clinical criterion + 3 Duke minor clinical criteria meets the standard for “definite” endocarditis.

Question 48

A child from upstate New York presents with erythema migrans.

What serology should you order on this patient?

Answer 48

None

Serology is negative in 90% of early-localized cases of Lyme disease; therefore, base the diagnosis on clinical findings. Erythema migrans is the pathognomic skin lesion of Lyme disease (Stage 1). You do not need to check Lyme serology on a patient with erythema migrans! Just treat!

Question 49

A 5-year-old boy from rural Arkansas presents with:

• Fever to 102.0° F (39.9° C)
• Swollen lymph node in his right inguinal area

What is the most likely diagnosis?

Answer 49

Tularemia (a.k.a. Rabbit Fever)

On exams, if you see a child from Arkansas (or Missouri or Oklahoma areas) with a swollen lymph node and fever, think tularemia, which is caused by Francisella tularensis. This is especially true if the patient is someone who hunts, traps, or handles rabbits. Treat with gentamicin or streptomycin for 10 days.

Question 50

A 16-month-old girl presents with:

• Thick, purulent nasal discharge
• Low-grade fever
• Decreased feeding
• Abdominal pain

What is the most likely diagnosis?

Answer 50

Streptococcosis

S. pyogenes is the only member of the group A beta-hemolytic streptococci (GABHS). Toddlers with GABHS upper respiratory infections do not present with pharyngitis, but rather with thick, purulent nasal discharge, low-grade fever, and decreased feeding (known as streptococcosis).

Question 51

A 6-year-old girl with sickle cell disease presents with:

• Fever
• Pain and swelling of her left thigh
• Bone scan shows increased uptake consistent with osteomyelitis.

What is the most likely cause of her osteomyelitis?

Answer 51

Salmonella

Osteomyelitis is an infection of bone that is usually bacterial in origin. Salmonella is the most common organism to cause osteomyelitis in sickle cell patients. In the general population, acute infection is typically caused by Staphylococcus aureus (most common by far).

Question 52

A child with fever and purpura is examined for an hour. It is later determined that the child has meningococcemia.

Should the primary care physician examining a child with meningococcemia receive rifampin or ciprofloxacin prophylaxis?

Answer 52

No

Health care workers should only take prophylaxis for meningococcus if they have close, intimate contact with oral secrections such as with intubation or mouth-to-mouth resuscitation.

Question 53

A 6-year-old with MRSA osteomyelitis is given his first dose of antibiotic. He develops the following:

• Tachycardia
• Flushing
• Generalized pruritus

What antibiotic was he likely given?

Answer 53

Vancomycin

If infused too rapidly, vancomycin can cause the “red man” syndrome. This is not a true allergy. It occurs because the rapid infusion of vancomycin results in mast cells degranulating and releasing histamine with its effects of tachycardia, flushing, and itching. This can be prevented by slowing the infusion rate or pre-treating with antihistamines.

Question 54

What commonly used antibiotic is definitely contraindicated in the breastfeeding mother?

Answer 54

Tetracycline

Tetracycline is also contraindicated for pregnant women. Aminoglycosides and chloramphenicol are commonly avoided for nursing mothers as well, but they are not an absolute contraindication. Quinolones are acceptable in nursing mothers but are contraindicated in pregnant women.

Question 55

An adolescent who recently immigrated from sub-Saharan Africa presents with:

• Low-grade fever
• Postauricular lymphadenopathy
• Headache
• Sore throat
• Macular rash on the face that has spread caudally to the neck and trunk

What is the most likely diagnosis?

Answer 55

Rubella (German Measles)

Rubella has been eliminated from the U.S. since 2004. Since 2015, it has been eliminated from the Americas. Today, < 10 people in the U.S. are reported as having rubella each year. Since 2012, all rubella cases had evidence that they were infected while outside the U.S. It continues to be endemic in many areas of the world.

Rubella presents with this pattern of a prodrome of fever, malaise, headache, and sore throat for a 1- to 5-day period before the rash appears. The rash can be very fleeting and changes appearance over time. It usually begins as macules on the face that spread quickly to the neck, trunk, arms, and finally the legs. Generally, the rash is gone from the face by the time it reaches the legs.

Question 56

A child from Connecticut presents with an isolated Bell’s palsy.

What diagnosis should you consider as the etiology of the Bell’s palsy?

Answer 56

Lyme Disease

Neurological problems can be symptoms of early disseminated (Stage 2) Lyme disease. Consider Lyme disease as a possible etiology if you see Bell’s palsy and/or foot drop in a patient from an endemic area.

Question 57

A 6-year-old boy develops bloody diarrhea and then has the following complications:

• Renal insufficiency
• Thrombocytopenia
• Hemolytic anemia

What is the etiology of the initial diarrhea and now these new findings?

Answer 57

E. coli O157:H7

E. coli O157:H7 is responsible for hemolytic uremic syndrome, which has the classic triad of renal failure, thrombocytopenia with purpura, and hemolytic anemia. Do not treat this infection with antibiotics because it has not been shown to be beneficial; in fact, adverse events can occur! Common reservoirs for E. coliO157:H7 include undercooked beef and unpasteurized milk or apple juice.

Question 58

A 5-year-old presents with:

• Abrupt onset of high fever
• Sore throat
• Dysphagia
• Tiny (1–2 mm) vesicles on the anterior pillars of the tonsils, uvula, and pharynx; no vesicles are noted on the front part of the mouth or lips

What is the most likely diagnosis?

Answer 58

Herpangina

Herpangina is most commonly due to coxsackievirus group A and presents in an abrupt fashion with the symptoms listed here. The pattern of where the vesicles occur differentiates herpangina from herpes simplex infection. In herpes simplex, lesions are more commonly in the front part of the mouth and extend onto the lips. In contrast, herpangina involves the back of the mouth, including the tonsils, uvula, and pharynx.

Question 59

A 3-year-old girl presents with:

• Painful rectal area
• Bright red, sharply demarcated rash that is very painful and itchy

What is the likely diagnosis?

Answer 59

Perianal Group A Streptococcal Cellulitis

Perianal group A streptococcal dermatitis/perirectal cellulitis is a brightly erythematous, sharply demarcated rash that is very painful and often itchy. It most commonly occurs in children between 6 months and 10 years of age.

Question 60

An 8-day-old infant presents with macules on the scalp that have become vesicular on a red base in the last few hours. They appear to be at the site of the infant’s fetal scalp monitor. The mother wonders if the site is infected. She has no history of infection during her pregnancy and is not known to be colonized with MRSA.

What is the most likely diagnosis?

Answer 60

Neonatal Herpes Simplex Virus (HSV) Infection

Neonatal HSV infections are localized to the skin, eye, mouth (SEM) region in ∼45% of cases, 30% in CNS only, and 25% are disseminated. Commonly (60–80%), the mother has no clinical history of herpes infection. Fetal scalp monitor sites are a common location, as well as eye margins and the presenting part. These are commonly misdiagnosed as staphylococcal infection. Never overlook HSV as a possibility in a neonate with a vesicular-looking lesion! HSV infection in the neonate is often severe, with high mortality and severe CNS sequelae even with appropriate antiviral therapy.

Question 61

Does treatment of nontyphoidal Salmonella gastroenteritis shorten the duration of the illness?

Answer 61

No

Therapy for Salmonella gastroenteritis not only does not shorten the duration of illness, it may prolong the carrier state. Only give antibiotic therapy (Ceftriaxone) for non-typhoidal Salmonella diarrhea to children < 3 months of age and older children with immunocompromising conditions (e.g., HIV/AIDS, agammaglobulinemia, malignancy, Crohn’s).

Question 62

• Occurs in infants < 1 month of age
• Maternal amnionitis
• Brown-staining of the amniotic fluid
• Preterm birth
• Pneumonia and septicemia
• Erythematous rash with papules, known as “granulomatosis infantisepticum”

What organism is associated with these findings?

Answer 62

Listeria monocytogenes

L. monocytogenes is a gram-positive rod. It causes infections in settings of decreased cellular immunity such as solid organ transplants, immunodeficiency, lymphoma, and leukemia, but it is also seen in neonates and pregnant women. In neonates, it is associated with the factors listed here. Neonates generally get the infection postnatally from their colonized mothers. Environmental sources of the organism include sheep, goats, other livestock, and poultry. Infection can also occur with direct contact with goat cheese, uncooked hot dogs, tofu, or contaminated vegetables.

Question 63

What is the treatment of choice for a group B Streptococcus (GBS) infection?

Answer 63

Ampicillin and Gentamicin, then Penicillin G

Ampicillin and gentamicin are started initially. (Gentamicin is synergistic with ampicillin and lowers the GBS bacterial load faster than ampicillin alone.)

When GBS is confirmed, treat with IV penicillin G alone (or ampicillin) for:

• 10 days for pneumonia or bacteremia
• 14–21 days minimum for meningitis (14 days is sufficient for uncomplicated meningitis)
• 3–4 weeks for septic arthritis or osteomyelitis

Question 64

A child with a cochlear implant is at increased risk of central nervous infection for what organism?

Answer 64

Streptococcus pneumoniae

S. pneumoniae is a normal inhabitant of the upper respiratory tract and is the most common cause of acute bacterial otitis media, sinusitis, and pneumonia in children < 5 years of age. Children with cochlear implants have an increased risk of pneumococcal meningitis.

Question 65

How does late-onset group B streptococcal infection present?

Answer 65

Bacteremia Without a Focus (50%) and Meningitis (40%)

Late-onset group B Streptococcus (GBS) disease occurs at a median onset of 27 days of life, with a range of 7 days to 3 months of life. Bacteremia without a focus is the most common presentation, with meningitis the next most common. Less than 10% present with osteomyelitis (especially proximal humerus) and septic arthritis (hip, knee, ankle).

Question 66

How many millimeters of induration are considered “positive” for a tuberculin skin test (TST) in a 3-year-old without any risk factors?

Answer 66

10 mm of Induration

Remember that children < 4 years of age are part of the moderate-risk group. Others in this group include:

• Homeless persons
• Those who have recently traveled to or were born in a high-prevalence region for TB
• IV drug abusers who are HIV negative
• Prisoners
• Health care workers; patients and staff of nursing homes
• Diabetics, chronic renal failure patients
• Persons undergoing immunosuppressive therapy (< 15 mg/day prednisone)

Question 67

A 2-month-old born vaginally presents with:

• No fever
• Staccato cough
• CXR evidence of pneumonia

What is the most likely etiology of the infant’s pneumonia?

Answer 67

Chlamydia trachomatis

C. trachomatis is commonly responsible for neonatal pneumonia in the first 4 months of life; 10–20% of newborns develop infection if born through a birth canal that is infected with this pathogen. Classically, the cough is described as a persistent staccato cough without fever.

Question 68

An 8-month-old presents with an initial history of fever for 4 days. The child was seen 2 days ago for a febrile seizure. The fever breaks today and a rash develops, which is why the mother returned with the child. The rash is macular-to-maculopapular and mainly on the trunk and extremities.

What is the diagnosis? What is the organism responsible?

Answer 68

Roseola (a.k.a. Exanthem Subitum, Sixth Disease);

Human Herpesvirus 6 (HHV-6)

By 3 years of age, nearly all children are infected with HHV-6, which can cause roseola. Roseola classically presents as described here, with fever for 3–5 days followed by the abrupt cessation of the fever and development of a macular-to-maculopapular rash. Seizures occur in up to 15% during the febrile stage. Human herpesvirus 7 (HHV-7) is a less frequent cause of roseola.

Question 69

A 14-year-old boy from Hawaii presents with the following:

• History of swimming in fresh-water lagoons
• Fever
• Myalgias
• Headache
• Jaundice

Laboratory:

• Bilirubin is disproportionately high compared to AST/ALT, which are each mildly elevated.
• Creatinine 1.9 mg/dL

What is the most likely diagnosis?

Answer 69

Leptospirosis

Leptospirosis is a spirochetal disease transferred by contact with contaminated water or infected animals. Rat and dog urine are the most common vectors. Many patients have a biphasic illness (2 phases separated by 3–4 days of no fever). Diagnose with urine studies after 4–7 days of illness.

Question 70

A NICU infant is found to have an IV catheter infection with Candida albicans.

How should this infection be managed?

Answer 70

Remove the Catheter and Start Systemic Antifungals

The key point here is that with fungal line infections, the catheter must be removed. Do not try to “treat through” and clear the catheter infection without removing the catheter. Amphotericin B is preferred for neonates; treat for at least 3 weeks when systemic candidiasis is present.

Question 71

A bat is found in the room of a 2-year-old boy where he was sleeping. His parents like to keep the windows cracked open to allow the cool Hawaiian breeze to come in.

Should he be given rabies prophylaxis?

Answer 71

No

In areas where rabies is found, of course you would provide rabies prophylaxis if you found a bat in the room of a sleeping child. But Hawaii is the only state in U.S. that is rabies free!

Question 72

Multiple patients present with diarrhea. It appears that a community-wide outbreak is occurring. It is thought that the drinking water might be contaminated with an acid-fast organism.

What is the likely organism?

Answer 72

Cryptosporidium

Suspect Cryptosporidium in a community-wide outbreak such as this. Sources can include contaminated city water, as well as water parks and swimming pools. The diarrhea can be prolonged but is self-limited in immunocompetent individuals. Diagnose by doing a specific stool Cryptosporidium antigen test.

Question 73

A 15-year-old girl presents with fever, weight loss, weakness, night sweats, and cough. She lives with her aunt, whose husband returned from jail about 5 months ago.

CXR shows hilar lymphadenopathy with a pleural effusion on the left. A subsequent pleural tap reveals:

• 2,000 WBC/µL—mostly lymphocytes
• Low glucose
• Elevated protein
• Elevated LDH
• Acid-fast bacilli (AFB) smear and culture are negative

What is the most likely diagnosis?

Answer 73

Tuberculosis (TB)

The girl has classic findings of TB, and her risk factor is living in a household with someone who was recently incarcerated. If she can produce sputum, stain and culture it for AFB and perform a tuberculin skin test (TST). Pleural biopsy is indicated if the sputum and pleural effusion are not diagnostic. Pleural effusions are typically AFB smear (and culture) negative, while pleural biopsy is much more sensitive for picking up active pulmonary TB.

Question 74

A 2-year-old African child from rural Chad presents with:

• Fever
• Paralysis that began in the proximal muscles of the thigh and progressively has involved more distal muscle groups

What is the most likely diagnosis?

Answer 74

Polio

Polio has essentially been eliminated from the Western Hemisphere and developed countries worldwide; however, Afghanistan, Pakistan, and Nigeria have never interrupted its transmission. In 2013, only 407 cases were reported globally, a decline of > 99% since 1988. Polio can be differentiated from Guillain-Barré syndrome by the patterns of the spread of paralysis. With Guillain-Barré, the paralysis begins distally and spreads proximally, opposite of polio.

Question 75

A 13-year-old girl who lives on a turkey farm presents with:

• Fever to 105.0° F (40.6° C)
• Myalgias
• Rigors
• Pneumonia
• Splenomegaly

What is the most likely etiology?

Answer 75

Chlamydophila psittaci

C. psittaci is found in psittacine (e.g., parrots, parakeets) and other birds and causes psittacosis (pneumonia and splenomegaly). With any pneumonia associated with poultry or pigeons, especially with splenomegaly, strongly suspect C. psittaci.

Differential: Histoplasma also causes pneumonia and splenomegaly + palatal ulcers; it is found in bird and bat droppings.

Question 76

An unimmunized 3-year-old presents with:

• Fever to 104.0° F (40.0° C)
• Dysphagia
• Drooling
• She also is leaning forward with her neck hyperextended and chin thrust forward.

What is the likely diagnosis?

Answer 76

Epiglottitis

Epiglottitis is rare today because of the widespread use of the Haemophilus influenzae Type b (Hib) vaccine, but it still occurs on occasion, especially in the unimmunized. It is important to keep the child comfortable and not upset her by trying to examine the oropharynx; you are likely to cause airway obstruction. The epiglottis is classically described as “cherry red.”

Question 77

The use of ointment in a newborn’s eyes is useful for preventing which infection(s): gonorrhea, Chlamydia, or both?

Answer 77

Gonorrhea

Contrary to popular belief, the use of eye prophylaxis is only beneficial in preventing gonorrheal infection; it does not prevent Chlamydia trachomatis infection.

Question 78

An HIV-infected 2-year-old boy with recurrent pneumonia and failure to thrive was brought to the emergency department for:

• Severe respiratory distress
• Hypoxemia
• Fever
• Lymphopenia
• CXR with diffuse infiltrates
• Bronchoalveolar lavage positive for silver-staining organism

What is the most likely diagnosis?

Answer 78

Pneumocystis Pneumonia (PCP)

PCP is due to Pneumocystis jiroveci, (formerly called Pneumocystis carinii), one of the more common pneumonia pathogens diagnosed in HIV-infected patients. Methenamine silver, toluidine blue O, calcofluor white, and fluorescein-conjugated monoclonal antibody are the most useful stains to identify the thick-walled cysts of P. jiroveci.

Question 79

A 17-year-old works in a pet store and spends most of his days cleaning the fish tanks of debris. He has had skin ulcerations on his right arm for several weeks that are unresponsive to cephalexin. Additionally, he was treated with doxycycline for MRSA without improvement.

What is the most likely etiology for his persistent skin ulcerations?

Answer 79

Mycobacterium marinum

Mycobacterium marinum is the “fish tank bacillus.” It causes nonhealing skin ulceration in people working around fish tanks. Often the lesions are along lymphatic channels. Treat with ethambutol + rifampin or clarithromycin + rifampin.

Question 80

A 10-year-old boy presents with:

• Sore throat
• Headache
• Fever
• Cervical lymphadenopathy
• Splenomegaly

What is the best way to test your suspected diagnosis?

Answer 80

Test for Epstein-Barr Virus (EBV)–Specific Antibodies

This patient most likely has EBV infection. Infectious mononucleosis is the most common clinical illness. Diagnosis is made by EBV-specific antibodies:

• If the IgM-viral capsid antigen (VCA) is positive, the patient has acute primary EBV or a very recent–past EBV infection.
• If the EB nuclear antigen (EBNA) is positive, the patient is convalescent or post-EBV.

Question 81

A Caucasian adolescent boy presents with hyperpigmented scaly lesions on his chest and back that worsen when he plays football in the hot sun.

What is the likely diagnosis?

Answer 81

Tinea Versicolor

Tinea versicolor is due to Malassezia furfur infection. It is very common in adolescents, particularly if there is exposure to heat and moisture (e.g., football practice) and occlusive clothing is being worn. A skin scraping will show the classic “spaghetti and meatballs” organisms. Treat with topical selenium sulfide or oral itraconazole.

Question 82

A child presents with mild antibiotic-associated colitis caused by Clostridium difficile. She has fever; labs indicate normal WBC and renal function. You treat her with oral metronidazole and her colitis resolves. She returns in 2 weeks with a recurrence.

What do you recommend for therapy now?

Answer 82

Oral Metronidazole

Recurrences of C. difficile infections occur in ∼ 25% of patients. Treat the initial recurrence with metronidazole if the disease remains mild to moderate. Oral vancomycin at this juncture is an acceptable, albeit expensive, alternative. Do not use metronidazole past the first recurrence. Treat 2^nd or subsequent recurrences with oral vancomycin in a prolonged, tapered regimen.

Question 83

A 17-year-old presents with:

• Low-grade fever
• Cough
• Wheezing
• Negative cold agglutinins

What is the most likely etiology for this patient’s pneumonia?

Answer 83

Chlamydophila pneumoniae

C. pneumoniae causes community-acquired pneumonia (CAP) in children > 5 years of age and adolescents. Bronchospasm is particularly prominent in respiratory infection caused by this pathogen. It can be treated with macrolides, including erythromycin or azithromycin. Tetracyclines and fluoroquinolones are also effective.

Question 84

A newborn presents with:

• IUGR
• Hepatosplenomegaly
• Jaundice
• Thrombocytopenia
• Petechia/purpura
• Microcephaly
• Cerebral atrophy
• Chorioretinitis
• Periventricular intracerebral calcifications

What is the most likely etiology of these signs and symptoms?

Answer 84

Congenital Cytomegalovirus (CMV) Infection

Congenital CMV infection occurs in ~ 1% of all newborns in the U.S. What determines the severity of the infection is whether or not the mother has IgG antibodies to CMV. If not, then there is an increased risk of this congenital syndrome occurring with dire consequences. This child has the most severe form of congenital CMV infection, cytomegalic inclusion disease. It can resemble toxoplasmosis, but remember that the cerebral calcifications are periventricular (they CircuMVent the ventricles) in CMV. In toxoplasmosis, they are scattered throughout the cerebrum. Congenital rubella can look like this as well with the petechia/purpura, otherwise known as “blueberry muffin” baby.

Question 85

A woman is infected with parvovirus B19 while pregnant.

What serious complication do you worry about in this case?

Answer 85

Hydrops Fetalis

Luckily, most infections with parvovirus B19 are asymptomatic and most mothers who are infected during pregnancy have infants without abnormalities. However, there is a risk of hydrops fetalis and possibly fetal loss.

Question 86

What is the most common organism to cause infection in cat bites?

Answer 86

Pasteurella multocida

P. multocida classically causes rapidly progressing cellulitis within 24 hours of the bite, often accompanied by fever and regional lymphadenopathy. It is the #1 cause of infection in a cat bite, followed by Staphylococcus aureus. Give antibiotics for all cat bites because cat teeth tend to cause deep puncture wounds. Amoxicillin/clavulanate is the drug of choice.

Question 87

A child presents with a history of an itchy bottom. The mother reports that she thought she saw some “rice” in the stool yesterday.

What is the most likely diagnosis?

Answer 87

Pinworms

Pinworm (Enterobius vermicularis) infection is very common. The pregnant female worm travels out the anus at night, leaving a trail of eggs on the surface of the skin. Diagnose by visualization of worms in the perianal region (they look like rice or small strands of spaghetti) or use the clear adhesive (scotch) tape test to collect eggs laid by the female worm during the night. Know that reinfection is common, as is autoinoculation.

Question 88

A 4-year-old presents with presumed bacterial meningitis.

What are the drugs of choice for empiric therapy?

Answer 88

Ceftriaxone (or Cefotaxime) and Vancomycin

Because of the increased penicillin resistance rates of Streptococcus pneumoniae, vancomycin has been added to the standard therapy of 3rd generation cephalosporins (ceftriaxone or cefotaxime) for children > 3 months of age suspected of having bacterial meningitis. This combination should be used empirically in all such patients. The antibiotics can be modified once you get the results of susceptibility testing.

Question 89

A 17-year-old homeless boy with history of current IV drug use (heroin) and multiple sexual partners (both male and female) presents with:

• Fever
• Lymphadenopathy
• Pharyngitis
• Erythematous maculopapular rash on the face, trunk, and extremities (including palms and soles)
• Mucocutaneous ulcers of the mouth and genitals
• Myalgias/arthralgias
• Negative monospot and negative rapid strep test

What is the most likely diagnosis?

Answer 89

Acute Retroviral HIV Syndrome

This constellation of signs and symptoms in a person at high risk is consistent with acute retroviral HIV syndrome. This typically occurs 2–4 weeks after the initial infection and lasts 1–2 weeks. Diagnose HIV acutely with an HIV-1 antibody/p24 screen. If positive, send for an HIV RNA PCR (viral load).

Question 90

What is the best empiric antibiotic therapy for meningitis in any child > 3 months of age?

Answer 90

IV Ceftriaxone or Cefotaxime plus IV Vancomycin

Empiric therapy for meningitis includes a 3^rd generation cephalosporin (ceftriaxone or cefotaxime) plus vancomycin because of increased S. pneumoniae resistance.

Question 91

A 10-year-old steps on a nail that goes through her tennis shoe.

What organism is most likely responsible if a cellulitis or other infection develops?

Answer 91

Pseudomonas aeruginosa

Consider P. aeruginosa in osteochondritis/osteomyelitis of the foot following a nail-puncture wound (especially if through a tennis shoe). It is also commonly the cause of endocarditis in IV drug abusers, bacteremia in burn patients, and chronic suppurative otitis externa (can be especially severe in diabetics).

Question 92

40% of the passengers on a cruise ship develop diarrhea.

What is the most likely etiology of the diarrhea?

Answer 92

Norovirus

Noroviruses cause ~ 50% of infectious viral gastroenteritis outbreaks in the U.S. and are responsible for the majority of “ship-wide” diarrhea outbreaks on cruise ships. The incubation period is only 1–2 days. Be careful on exams if they say it is only a few people on a cruise ship who ate at a buffet—in that case, it is more likely a preformed toxin-like Staphylococcus or Bacillus species.

Question 93

A 6-month-old with beta-thalassemia has fever; the blood culture is growing a gram-negative rod.

What organism should you suspect?

Answer 93

Yersinia enterocolitica

Bacteremia with Y. enterocolitica is more common in children < 1 year of age and in older children with iron overload, especially those who are transfusion dependent (e.g., sickle cell disease, beta-thalassemia, aplastic anemia).

Question 94

What is the main side effect of zidovudine (ZDV)?

Answer 94

Bone Marrow Suppression

ZDV is the oldest of the antiretroviral drugs, but it still remains very useful. For example, when given prophylactically to HIV+ pregnant patients during pregnancy, labor, and delivery (and to the newborn), ZDV reduces the risk of perinatal transmission of HIV by nearly 70%. It is well tolerated at currently used doses, but it does cause bone marrow suppression (e.g., anemia, granulocytopenia). It also causes myopathy.