Chapter 7 - ID Flashcards

1
Q

Which organisms are most likely to cause serious bacterial illness, namely sepsis or meningitis, in the following age groups and what are the empiric antibiotics of choice based on this?

  • 0 to 1 month
  • 1 to 3 months
  • 3 to 36 months
  • 3 years and older
A
  • 0-1 month: GBS, E. coli, Listeria - treat with ampicillin + gentamicin or cefotaxime
  • 1-3 months: GBS, S. pneumoniae, Listeria - treat with ampicillin + cefotaxime + vancomycin if bacterial meningitis is suspected
  • 3-36 months: S. pneumoniae, H. influenza type b, N. meningitidis - treat with cefotaxime + vancomycin if bacterial meningitis is suspected
  • older: S. pneumoniae, N. meningitidis - treat with cefotaxime + vancomycin if bacterial meningitis is suspected
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2
Q

What is fever of unknown origin?

A

a fever lasting longer than 8 days to 3 weeks without a primary diagnosis

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3
Q

Bacterial Meningitis

A
  • risk factors are young age, especially in the first month of life, immunodeficiency, and anatomic defects
  • GBS, E. coli, Listeria, S. pneumoniae, H. influenzae type b, and N. meningitidis are the most common organisms depending on age
  • infants and young children may have nonspecific signs with an absent or minimal fever and bulging fontanelle
  • older children often present with fever, altered consciousness, nuchal rigidity, seizures, photophobia, emesis, and headache
  • children with suspected bacterial meningitis should receive a lumbar puncture, blood culture, and CT scan with contrast to evaluate for brain abscesses
  • CSF culture may be sterile if antibiotics have been started, but the biochemical profile should be unchanged
  • elevated WBC with predominately PMNs, high protein, low glucose, and a positive culture/gram stain
  • treat with empiric antibiotics based on age and likely organism, corticosteroids to reduce the incidence of hearing loss in HIB meningitis, and supportive care
  • most often complicated when due to a gram-negative or S. pneumoniae; may be complicated by hearing loss, global brain injury, SIADH, seizures, hydrocephalus etc.
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4
Q

What are the primary complications of bacterial meningitis?

A
  • hearing loss
  • global brain injury
  • SIADH
  • seizures
  • hydrocephalus
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5
Q

Describe the CSF profile in someone with the following types of meningitis:

  • acute bacterial
  • partially treated bacterial
  • viral
  • tuberculosis
  • fungal
  • parameningeal focus
A
  • acute bacterial: elevated WBC with predominately PMNs, high protein, low glucose, and positive culture/stain
  • partially treated bacterial: elevated WBC with predominately monocytes, normal to high protein, low glucose, and a negative culture/stain
  • viral: PMNs early, then monocytes and lymphocytes, normal to high protein, normal glucose; enterovirus may be cultured, HSV encephalitis may show RBCs
  • tuberculosis: slightly elevated WBC with predominately lymphocytes, very high protein content, low glucose
  • fungal: slightly elevated WBC with predominately lymphocytes
  • normal to high protein, low glucose
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6
Q

Aseptic Meningitis

A
  • inflammation of the meninges with a CSF lymphocytic pleocytosis
  • viral meningitis is the most common form with enteroviruses being the predominate agent
  • clinical features resemble bacterial meningitis with fever, altered consciousness, nuchal rigidity, seizures, photophobia, emesis, and headache
  • typically CSF WBC is elevated but to a lesser extent than in bacterial cases and there are predominately PMNs early but then monocytes and lymphocytes; protein is normal or high and glucose is normal
  • most cases are self-limited and require only supportive therapy
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7
Q

M. tuberculosis Meningitis

A
  • an aseptic bacterial meningitis
  • most common in children younger than 5 years old
  • presents with lethargy or irritability which progresses rapidly to cranial nerve deficits, altered consciousness, coma, paraplegia, and death
  • has a slightly elevated WBC with predominately lymphocytes, protein is high, and glucose is low
  • likely to find a characteristic basilar enhancement on neuroimaging and a positive culture or PCR
  • treated with RIPE therapy
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8
Q

Simple Upper Respiratory Infection

A
  • also known as the common cold, which can be caused by a number of viruses including rhinovirus, parainfluenza, and coronavirus
  • presents with low-grade fever, rhinorrhea, cough, and sore throat, which resolve within 7-10 days; persistent symptoms beyond 10 days warrant evaluation for bacterial superinfection
  • treat with hydration and exclusion of more serious disorders
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9
Q

Describe development of the sinuses.

A
  • the ethmoid and maxillary sinuses are present at birth
  • the sphenoid sinuses develop between 3-5 years of age
  • frontal sinuses arise between 7-10 years of age
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10
Q

Sinusitis

A
  • most often caused by S. pneumoniae, H. influenzae, or M. catarrhalis
  • clinical features help classify it as acute persistent, acute severe, subacute, or chronic
  • acute severe presents with purulent nasal discharge for 3-5 days and has a high fever
  • acute persistent presents with nasal discharge and cough for 10-30 days and may also have headache, malodorous breath, facial pain, or low-grade fever
  • subacute has these same symptoms for 30-90 days and chronic lasts more than 90 days
  • chronic should be evaluated for an underlying condition like CF or involvement of S. aureus or an anaerobe
  • acute and subacute are treated with amoxicillin, amoxicillin-clavulanate, or second generation cephalosporin for 10-14 days
  • chronic is typically treated with a trial of broad-spectrum oral antibiotics and CT imaging
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11
Q

Viral Pharyngitis

A
  • there are many causes including those involved in simple URI
  • presents with low-grade fever, rhinorrhea, cough, and sore throat in addition to tonsils exudates
  • specifically, EBV pharyngitis may present with enlarged posterior cervical lymph nodes, malaise, and hepatosplenomegaly; coxsackievirus pharyngitis presents with herpangina
  • managed with supportive care, analgesics, and maintenance of adequate hydration; EBV pharyngitis may require corticosteroids
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12
Q

Strep Pharyngitis

A
  • caused by S. pyogenes (GABHS)
  • presents with a lack of other URI symptoms, petechiae on the soft palate, strawberry tongue, and enlarged tender anterior cervical lymph nodes, fever, and scarlatiniform rash
  • culture is the gold standard for diagnosis but is slow so antigen testing is a common substitute in the short-term
  • treated with oral penicillin, single dose IM penicillin, or oral erythromycin or macrolides
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13
Q

Corynebacterium diphtheriae

A
  • gram positive rods which are club-shaped, contain metachromatic granules, and form V or Y shapes
  • spread via respiratory droplets, colonize the oropharynx, and may spread in the blood
  • they produce an extoxin encoded by beta-prophage, which ADP-ribosylates and inactivates EF-2, inhibiting protein production by host cells
  • the bacteria cause “bull neck” lymphadenopathy, pseudomembrane formation in the oropharynx, a potentially fatal myocarditis with heart block and arrhythmia, and nerve deficits beginning in the posterior pharyngeal wall
  • diagnosis is made by culture on cystine-tellurite or Loeffler’s medium in combination with the Elek’s test to distinguish toxigenic species from nontoxigenic ones
  • treated with oral erythromycin or parenteral penicillin
  • toxoid vaccine is available (DTaP)
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14
Q

Acute Otitis Media

A
  • an acute infection of the middle ear space
  • most commonly caused by S. pneumoniae, non-tapeable H. influenzae, or Moraxella catarrhalis
  • presents with fever, ear pain, and decreased hearing; there may be drainage if the tympanic membrane perforates
  • diagnosis requires identification of fluid in the middle ear space with symptoms; fluid is most reliably detected using a pneumatic otoscope since erythema and loss of tympanic membrane landmarks are unreliable
  • treated with amoxicillin, amoxicillin-clavulanic acid, or cephalosporin
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15
Q

What is an otitis media with effusion?

A

defined as fluid within the middle ear space without symptoms of infection

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16
Q

Otitis Externa

A
  • risk factors are those that interfere with the protective mechanisms of the outer ear: cerumen removal, trauma, maceration of the skin from swimming, or excessive moisture
  • P. aeruginosa, S. aureus, and Candida albicans are the most common organisms
  • presents with pain, tenderness on palpation or movement of the tragus, itching, and drainage; systemic symptoms are usually absent
  • diagnosis is based on erythema and edema of the external auditory canal
  • treated with restoration of the canal’s acidic environment: use acetic acid solution for mild cases and add topical antibiotics for more severe cases
  • if a perforated AOM is complicated by OE, treat with both oral and topical antibiotics
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17
Q

Cervical Lymphadenitis

A
  • present as enlarged, tender, warm, and mobile nodes with overlying erythema in the cervical area
  • S. aureus is the most common bacterial agent but S. pyogenes, mycobacterium, and B. henselae are also seen
  • other causes include reactive lymphadenitis, viral lymphadenitis, Kawasaki disease, or T. gondii
  • managed with empiric antibiotics directed toward S. aureus and S. pyogenes, including a first-generation cephalosporin or anti-staph penicillin
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18
Q

What is cervical reactive lymphadenitis?

A

an enlarged, inflamed, tender lymph node in the cervical area that occurs in response to infections of the pharynx, teeth, or soft tissues of the head and neck

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19
Q

What typically distinguishes Kawasaki disease-related lymphadenitis from other causes?

A

Kawasaki disease usually presents with unilateral cervical lymphadenitis rather than bilateral

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20
Q

Parotitis

A
  • an inflammation of the parotid salivary glands
  • bilateral cases are usually caused by mumps and other viruses while bacterial parotitis caused by S. aureus, S. pyogenes, and M. tuberculosis result in unilateral parotitis
  • presents with swelling centered above the angle of the jaw, fever, and sometimes pus expressed from Stensen’s duct
  • diagnosed based on culture from the Stensen’s duct drainage in the case of bacterial parotitis and by viral serology in viral parotitis
  • treated with supportive care, analgesics, and antibiotics if bacterial
  • may be complicated by meningoencephalitis, orchitis, epididymitis, or pancreatitis as well as abscess and osteomyelitis of the jaw
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21
Q

Impetigo

A
  • a superficial infection of the upper dermis
  • usually caused by S. aureus or GABHS
  • presents with lesions that have a honey-colored crust; fever is generally absent
  • treated with topical mupirocin or oral antibiotics
  • may be complicated by post-streptococcal glomerulonephritis or staphylococcal scalded skin syndrome depending on the offending organism
22
Q

Erysipelas

A
  • an infection of the dermal lymphatics
  • usually caused by GABHS
  • presents with tender, erythematous skin that has a distinct border
  • treated with antibiotics directed at GABHS
  • may be complicated by bacteremia, post-streptoccal glomerulonephritis, and necrotizing fasciitis
23
Q

Cellulitis

A
  • a skin infection that occurs within the dermis
  • caused by GABHS and S. aureus, usually following a break in the skin
  • presents as an erythematous, warm, tender area that has an indistinct border
  • diagnosed by visual inspection and blood cultures are seldom positive; culture of biopsy can be performed if aggressive
  • treated with first generation cephalosporins or anti-staphylococcal penicillins
24
Q

How is erysipelas differentiated from cellulitis?

A

erysipelas is a lesion with distinct borders whereas cellulitis has indistinct borders

25
Q

Buccal Cellulitis

A
  • an uncommon variant of cellulitis
  • presents with a fever and unilateral bluish discoloration of the cheek in young, unimmunized children
  • caused by type b H. influenzae
  • treated with second or third generation cephalosporin
  • there is a high rate of concomitant bacteremia and meningitis, so a lumbar puncture should be performed
26
Q

Perianal Cellulitis

A
  • a variant of cellulitis
  • caused by GABHS
  • presents with a well-demarcated erythematous lesion around the anus; may also have constipation
  • treated with oral antibiotics
27
Q

Necrotizing Fasciitis

A
  • a potentially fatal form of deep cellulitis
  • typically polymicrobial
  • presents with pain and systemic symptoms out of proportion to the physical findings
  • requires IV antibiotics and surgical debridement of the affected area
28
Q

Staphylococcal Scalded Skin Syndrome

A
  • a variant of cellulitis caused by S. aureus species that produce an exfoliative toxin
  • presents with fever, tender skin, and bullae; large sheets of skin slough and there is a positive Nikolsky sign
  • treat with good wound care and IV antibiotics
29
Q

Scarlet Fever

A
  • a toxin-mediated bacterial illness presenting with a characteristic skin rash
  • caused by GABHS, which produce an erythrogenic toxin, and transmitted via large respiratory droplets
  • presents with fever, chills, malaise, and exudative pharyngitis before or during the exanthem
  • the exanthem begins on the trunk, is erythematous with tiny skin-colored papules, blanches, has a texture of sandpaper, has localized petechiae in a linear distribution, and involves desquamation of dry skin
  • diagnosed according to clinical features and a positive throat culture for S. pyogenes
  • treated with penicillin
  • may be complicated by post-strep glomerulonephritis, rheumatic fever, post-strep arthritis, or pediatric autoimmune neuropsychiatric disorders associated with Streptococcal infection
30
Q

What is post-streptococcal arthritis?

A

joint symptoms without the other features of rheumatic fever which follow GABHS infection and last for weeks

31
Q

What is pediatric autoimmune neuropsychiatric disorders associated with Streptococcal infection?

A

the acute onset of obsessive-compulsive symptoms shortly after a streptococcal infection, which can be prevented with penicillin during the initial infection

32
Q

Toxic Shock Syndrome

A
  • a toxin-mediated illness most often caused by S. aureus but also by GABHS
  • diagnosis requires 5 of the following 6: fever higher than 38.5, hypotension, diffuse macular erythroderma, desquamation occurring 10-14 days after onset of the illness, multisystem involvement of 3 or more systems, and negative cultures of blood, CSF, and pharynx
  • historically caused by S. aureus in young women who left in tampons for a prolonged period of time
  • treated with supportive therapy, anti-staphylococcal antibiotics, and removal of the nidus
33
Q

Rotavirus

A
  • an RNA virus spread via the fecal-oral route, most commonly seen during the winter months
  • it is the most common infectious agent causing gastroenteritis
  • presents with vomiting, diarrhea, and dehydration lasting 4-7 days
  • diagnosed based on stool ELISA; WBCs are absent from stool
  • treatment is supportive
  • may be complicated by a post-infection transient lactose intolerance
34
Q

Norwalk Virus

A
  • an RNA virus spread via the fecal-oral route, most commonly seen in closed populations
  • presents as gastroenteritis with predominately vomiting, which lasts 2-3 days
  • treatment is supportive
35
Q

ETEC

A
  • a lactose-fermenting, encapsulated, catalase-positive, gram-negative, which forms green colonies on EMB agar
  • commonly referred to as traveler’s diarrhea and found in contaminated water sources, usually in developing nations
  • utilizes a heat-labile enterotoxin, which increases cAMP, and a heat-stable enterotoxin, which increases cGMP, to cause a non-invasive, watery diarrhea
  • WBCs are absent from the stool and it is a clinical diagnosis
  • treat with quinolones or sulfonamides to shorten the duration while maintaining hydration
36
Q

Enteropathogenic E. coli (EPEC)

A
  • a lactose-fermenting, encapsulated, catalase-positive, gram-negative, which forms green colonies on EMB agar
  • presents as noninvasive, water diarrhea
  • WBCs are absent in stool and diagnosis is made via culture
  • treat with oral quinolones or sulfonamides while maintaining hydration status
37
Q

Enterohemorrhagic E. coli (EHEC)

A
  • a lactose-fermenting, encapsulated, catalase positive gram-negative, which forms green colonies on EMB agar
  • unique in that they do not ferment sorbitol like most other species of E. coli
  • commonly contaminates undercooked meats and O157:H7 is the most important serotype
  • utilize a shiga-like toxin which inhibits the 60S ribosomal subunit and thus cause bloody diarrhea as well as HUS
  • WBCs can be found in stool and culture is diagnostic
  • avoid antibiotics if HUS is present
38
Q

Shigella sonnei

A
  • an immotile, acid-stable, facultative intracellular, gram-negative bacillus, which forms green colonies on Hektoen enteric agar, differentiating it from salmonella
  • taken up by M cells and spread via actin-rockets, using a T3SS and shiga toxin to inhibit the 60S ribosomal subunit of host cells
  • causes an inflammatory, bloody diarrhea usually in children under 10 years old
  • WBCs are present in stool and culture is diagnostic
  • may be complicated by HUS or seizures secondary to neurotoxin release
  • treat with third-generation cephalosporins or fluoroquinolones
39
Q

Salmonella spp.

A
  • a bacterial cause of diarrhea, which can be bloody or nonbloody
  • spread via the fecal-oral route, poultry, milk, eggs, and exposure to lizards or turtles
  • WBCs may be present or absent in stool and culture is diagnostic
  • treatment is not indicated for uncomplicated cases in hosts older than three months; invasive disease should be treated with a third-generation cephalosporin
  • patients with sickle cell disease may develop bacteremia or osteomyelitis
40
Q

Campylobacter jejuni

A
  • an oxidase positive, curved, gram-negative rod
  • thermophilic and prefers to grow at 42 degrees Celsius
  • contaminates poultry and causes a bloody diarrhea
  • WBCS are usually present if blood is present
  • can be treated with oral erythromycin but symptoms commonly resolve without treatment
  • may also be complicated by either reactive arthritis or Guillain-Barre syndrome with an ascending paralysis
41
Q

Yersinia enterocolitica

A
  • an encapsulated, gram-negative bacillus that survives cold temperatures well
  • known for its bipolar, “safety pin” staining
  • found in puppy feces and contaminated dairy products
  • causes a bloody diarrhea and may present with right lower quadrant pain, mimicking appendicitis
  • diagnosis is based on culture of stool or mesenteric lymph node
  • treated with third-generation cephalosporins
42
Q

Clostridium difficile

A
  • an obligate anaerobe, spore-forming, gram positive rod
  • often seen as a nosocomial infection in those who have been taking clindamycin or ampicillin
  • spread by healthcare workers who don’t wash their hands well
  • exotoxin A, aka enterotoxin, targets the brush border, damages the mucosal lining of the colon, and causes watery diarrhea
  • exotoxin B, aka cytotoxin, causes actin depolymerization, necrosis of colonic mucosal surfaces, and the formation of pseudomembranes
  • diagnosis is made using a PCR TOXIN ASSAY of the stool
  • treat with oral vancomycin or metronidazole
43
Q

Vibrio cholerae

A
  • an acid-labile, oxidase-positive, “comma-shaped” gram-negative bacillus
  • spread via the fecal-oral route and is endemic to South American countries with poor sanitation
  • it uses fibrae to attach the the wall of the intestine but does not invade; instead, it secretes cholera toxin, which constitutively activates AC and increases cAMP levels
  • causes a watery diarrhea described as “rice water stool” with massive water loss
  • diagnosed in the US via serology
  • treat with fluid replacement
44
Q

Diarrhea causes what sort of electrolyte imbalance?

A

a non-angio gap hyperchloremic metabolic acidosis due to bicarbonate loss

45
Q

HIV

A
  • a virus acquired in utero, intrapartum, or postpartum via breastfeeding, via sexual contact, or parenterally
  • risk of transmission is increased by a high maternal viral lode, primary maternal infection, concomitant maternal genital infections, premature birth and prolonged rupture of membranes; decreased by c-section, maternal antiretroviral therapy, and post-exposure prophylaxis with 6 weeks of zidovudine as well as avoidance of breastfeeding
  • usually asymptomatic in the first year of life but may exhibit failure to thrive, thrombocytopenia, recurrent infections, lymphadenopathy, parotitis, thrush, loss of developmental milestones, and severe varicella
  • infants born to HIV-postivie mothers will have maternal antibody that persists for 18-24 months; monitor this as well as HIV-specific DNA via PCR
  • PCR is performed monthly, and if negative at 4 months, is indicative of an uninfected child; continue to follow antibody levels until 18-24 months or absent
  • may be complicated by PCP infection (fever, hypoxia, and interstitial pulmonary infiltrates), M. avium complex, fungal infection, viral infection, toxoplasmosis, or cryptosporidium
  • in high-risk individuals, use TMP/SMX for PCP prophylaxis until 4 months of age and perform urine CMV culture to detect connection
  • antiretroviral therapy should be used once infection has been confirmed and continue prophylaxis for PCP and CMV
  • infected individuals should get all routine childhood vaccines except the live varicella vaccine (live MMR is still recommended), annual influenza, pneumococcal vaccine, and annual TB skin testing; they also need monitoring of T-cells and viral load and annual ophthalmologic examination to assess for CMV retinitis
46
Q

Infectious Mono

A
  • a lymphocytic leukocytosis comprised of CD8 T cells
  • most commonly due to EBV with CMV infection less common
  • primarily infects the oropharynx, liver, and B cells causing pharyngitis and hepatitis
  • presents as fever, fatigue, exudative pharyngitis, posterior cervical lymphadenopathy, hepatosplenomegly, and macular or scarlatiniform rash
  • CD8 response leads to generalized lymphadenopathy due to hyperplasia in the paracortex and splenomegaly due to hyperplasia in the periarterial lymphatic sheath
  • increased risk of splenic rupture, ampicillin rash, and B-cell lymphoma
  • screen using the mono spot test, which detects IgM antibodies that cross-react with horse or sheep RBCs (called heterophiles antibodies) one week after infection
  • a negative monospot test suggests CMV rather than EBV
  • monospot testing is less sensitive in children under the age of four and these individuals should be tested with eBV antibody titers: should see elevated levels of viral capsid antigen-IgM and absent Epstein Barr nuclear antigen antibodies because these appear 2-3 months after infection
  • definitively diagnosed based on serologic testing for the EBV viral capsid
47
Q

Pneumocystis carinii pneumonia

A
  • the most common opportunistic infection in HIV-infected children
  • presents with fever, hypoxia, and interstitial pulmonary infiltrates
  • use TMP/SMX as prophylaxis in at risk individuals
48
Q

What is an amoxicillin-associated rash?

A

a diffuse pruritic maculopapular rash seen 1 week after starting the antibiotic, which is an idiosyncratic reaction in those with infectious mono and is not an allergic reaction

49
Q

Measles

A
  • an RNA virus of the paramyxoviridae family
  • presents with a prodrome of the three C’s: cough, conjunctivitis, and coryza; there may also be photophobia and low-grade fever
  • this is followed by an enanthem with Koplik spots, small gray papules on an erythematous base which are transient and may be absent by the time the patient presents
  • an erythematous maculopapular eruption is seen next, beginning around the neck and ears before spreading to the chest and upper extremities; if affects the lower extremities by day 2, is confluent on day 3, and lasts 4-7 days
  • treat with supportive care and vitamin A
  • may be complicated by bacterial pneumonia, otitis media, laryngotracheitis, encephalomyelitis, or subacute sclerosing panencephalitis years later
50
Q

Rubella

A
  • an RNA virus of the togavirus family
  • shorter and milder than measles
  • presents with a prodrome of URI symptoms and low-grade fever, followed by painful lymphadenopathy of the sub occipital, posterior auricular, and cervical nodes
  • a non-pruritic, maculopapular, and confluent exanthem follows, beginning on the face and spreading to the trunk, lasting a total of 3-4 days
  • diagnosed with viral culture and serology
  • treatment is supportive
  • may be complicated by meningoencephalitis, polyarteritis, or congenital rubella syndome (congenital cataracts, sensorineural hearing loss, and PDA)
51
Q

What is congenital rubella syndrome?

A
  • the most serious complication of rubella
  • occurs following primary maternal infection during the first trimester
  • presents with thrombocytopenia, hepatosplenomegaly, jaundice, and purpura
  • the major complications, however, are PDA, congenital cataracts, and sensorineural hearing loss