LE 4 (INFECTIOUS/ ALLERGY) 2026 Flashcards
Each of the following statements about measles is TRUE, EXCEPT:
A. Koplik spots appear 1 to 4 days before the onset of rash
B. The peak of contagiousness occurs during the rash, which lasts for 7–10 days
C. The patient is infectious both before and after the appearance of the rash
D. Both active and passive immunization can help prevent measles
Which of the following statements about congenital rubella syndrome (CRS) is NOT true?
A. It is diagnosed if the infant has IgM antibodies at birth
B. It can be diagnosed if IgG antibodies persist beyond 6 months of age
C. Infection after 16 weeks of gestation commonly results in major congenital anomalies
D. CRS is associated with sensorineural deafness, cataracts, and congenital heart disease
Which of the following statements about Herpes Simplex Virus (HSV) is CORRECT?
A. Most neonatal herpes is caused by HSV type 1
B. Primary HSV infection in infants usually leads to fever lasting 4–9 days
C. HSV type 1 is the most common cause of herpes labialis
D. HSV type 2 can be treated effectively with immunoglobulin
A 4-year-old child is diagnosed with varicella (chickenpox). The child’s aunt is pregnant, and the family is asking when it is safe for the child to be around her.
Question:
When is the earliest it is safe for this child to meet his pregnant aunt?
A. As soon as the fever resolves
B. When the vesicles begin to crust over
C. Once all lesions are fully crusted
D. Two weeks after the rash first appears
What should be given if a newborn presents with cicatricial scarring?
A. Acyclovir
B. Varicella vaccine
C. Intravenous immunoglobulin
D. Varicella-zoster immune globulin (VZIG)
A young child develops high intermittent fever for 3–5 days. When the fever subsides, a rash suddenly appears on the trunk and then spreads to the face and extremities. The child is otherwise well-appearing.
Question:
Which virus is most likely responsible for this clinical picture?
A. Human herpesvirus 6 (HHV-6)
B. Parvovirus B19
C. Rubella virus
D. Coxsackievirus A16
An 18-month-old child presents with hemolytic anemia, thrombocytopenia, azotemia, and anuria, following an episode of bloody diarrhea.
Question:
What is the most likely etiologic agent?
A. Shigella dysenteriae
B. Enterohemorrhagic E. coli (EHEC)
C. Salmonella typhi
D. Campylobacter jejuni
Which of the following viral exanthems is associated with congenital infection that may result in cataracts, sensorineural deafness, and congenital heart disease?
A. Measles
B. Varicella
C. Rubella
D. Roseola infantum
Each of the following has been associated with Ascaris lumbricoides infection in humans, EXCEPT:
A. Löffler-like syndrome
B. Urticaria
C. Anemia
D. Intussusception
A 3-year-old child presents with:
* Low-grade fever
* Cough
* Leukocytosis: 90,000/mm3
* 90% neutrophils
Question:
Given this presentation, what is the most likely etiologic agent?
A. Ancylostoma duodenale
B. Enterobius vermicularis
C. Ascaris lumbricoides
D. Toxocara canis
Which of the following parasites does NOT infect via the percutaneous route?
A. Strongyloides stercoralis
B. Ancylostoma duodenale
C. Schistosoma spp.
D. Echinococcus granulosus
A 14-year-old adolescent presents with:
* Low-grade fever
* Generalized maculopapular rash (face → trunk → extremities)
* Posterior cervical and postauricular lymphadenopathy
* Mild conjunctivitis (red eyes)
* Joint pains (arthralgia)
Question:
What is the most likely diagnosis?
A. Measles
B. Rubella (German measles)
C. Roseola infantum
D. Scarlet fever
The Sabin-Feldman dye test is used in the diagnosis of which of the following infections?
A. Cytomegalovirus
B. Rubella
C. Toxoplasma gondii
D. Herpes simplex virus
What is the most common fungal infection in neonates?
A. Candida parapsilosis
B. Cryptococcus neoformans
C. Aspergillus fumigatus
D. Histoplasma capsulatum
A 3-year-old boy presents with:
* Fever for 3 days
* Red throat with tender, enlarged cervical lymph nodes
* Slight resistance to neck flexion
Question:
What is the next best step in management?
A. Perform lumbar puncture
B. Start empiric antibiotics
C. Obtain throat swab for culture
D. Give antipyretics and observe
What is the leading cause of bacterial meningitis in children between the ages of 6 months and 3 years (in unvaccinated populations)?
A. Neisseria meningitidis
B. Streptococcus pneumoniae
C. Haemophilus influenzae type b
D. Listeria monocytogenes
Which of the following parasites does NOT cause disease during its migration through parenchymal tissues?
A. Ascaris lumbricoides
B. Schistosoma spp.
C. Strongyloides stercoralis
D. Enterobius vermicularis
Which parasitic infection causes a type of dermatitis commonly referred to as “ground itch”?
A. Enterobius vermicularis
B. Ancylostoma duodenale
C. Trichuris trichiura
D. Taenia solium
Cysticercosis is caused by which of the following parasites?
A. Taenia saginata
B. Echinococcus granulosus
C. Diphyllobothrium latum
D. Taenia solium
A 2-year-old child presents with:
* High-grade fever (up to 40°C)
* Lethargy
* Vesicular rash
* New lesions continue to appear over the next 4 days, especially in the
afternoon
* Lesions at different stages of evolution (macules, papules, vesicles, crusts)
Question:
What is the most likely diagnosis?
A. Measles
B. Scarlet fever
C. Varicella (chickenpox)
D. Roseola infantum
A 2-year-old child is brought to the clinic due to intense perianal itching (pruritus ani), especially at night. The child is otherwise active and healthy.
Question:
What is the most likely cause of this symptom?
A. Giardia lamblia
B. Strongyloides stercoralis
C. Enterobius vermicularis
D. Ascaris lumbricoides
A 4-month-old infant presents with a 4-week history of:
* Gagging, gasping, paroxysmal cough
* Afebrile
CBC reveals:
* WBC: 42,000/mm’ with lymphocytic predominance
* 10% atypical (crescent-shaped) lymphocytes
* Hemoglobin: 12 g/dL
* Platelets: 650,000/mm3
Question:
What is the most likely etiologic agent?
A. Mycoplasma pneumoniae
B. Respiratory syncytial virus (RSV)
C. Bordetella pertussis
D. Cytomegalovirus
An asymptomatic newborn was exposed to smear-positive TB and has been receiving INH prophylaxis for 3 months.
Question:
What should be done next?
A. Continue INH
B. Stop INH
C. Start Rifampicin
D. Perform Mantoux test and re-evaluate
A patient presents with a 2-week history of:
* Intermittent low-grade fever that is gradually increasing
* Headache
* Malaise
* Dry cough
* Abdominal pain
There is no obvious localizing sign, and the fever is persistent.
Question:
What is the most likely diagnosis?
A. Typhoid fever
B. Dengue fever
C. Pulmonary tuberculosis
D. Infectious mononucleosis
What is the most common cause of viral pneumonia in infancy?
A. Influenza A
B. Adenovirus
C. Respiratory syncytial virus (RSV)
D. Parainfluenza virus
A 1.5-year-old child who attends a child care center 5 days a week is diagnosed with meningococcal infection. Close contacts, such as classmates and household members, need chemoprophylaxis.
Question:
Which of the following antimicrobials is the most appropriate for prophylaxis in close contacts of a meningococcal case?
A. Ampicillin
B. Trimethoprim-sulfamethoxazole
C. Ciprofloxacin
D. Rifampicin
E. Sulfonamides
Which of the following is NOT a preferred diagnostic test for HIV infection in neonates?
A. HIV culture
B. HIV RNA PCR
C. HIV DNA PCR
D. HIV ELISA
Passive immunization with measles immunoglobulin is effective in preventing or modifying the course of measles if administered within how many days of exposure?
A. 2 days
B. 4 days
C. 6 days
D. 9 days
Which of the following best describes the skin lesion of Herpes Zoster?
A. Diffuse maculopapular rash
B. Vesicles on palms and soles
C. Vesicular, clustered lesions along one or two adjacent dermatomes
D. Target lesions with central clearing
Which of the following is NOT a feature of mumps?
A. Caused by a paramyxovirus
B. Orchitis is a possible complication
C. Complications are more common in adults
D. Aseptic meningitis is a complication only seen in children
Which of the following is TRUE about the incubation period of mumps?
A. Less than 1 week
B. 7–10 days
C. Less than 2 weeks
D. More than 2 weeks
D. More than 2 weeks
Rationale:
The incubation period of mumps is typically 16 to 18 days, but it can range from 12 to 25 days. This means it is more than 2 weeks in many cases, making Option D the correct choice.
A child presents with:
* Microcephaly
* Hepatosplenomegaly
* Periventricular calcifications (seen on cranial imaging)
Question:
What is the best specimen site to obtain for confirming the diagnosis of congenital
Cytomegalovirus (CMV) infection?
A. Blood
B. Cerebrospinal fluid (CSF)
C. Urine
D. Saliva
E. Stool
A 2-year-old child, partially immunized, is exposed to his brother diagnosed with diphtheria.
Question:
What is the appropriate prophylactic antibiotic for this exposed child?
A. Anti-diphtheria serum only
B. Penicillin
C. Erythromycin
D. Tetanus toxoid
E. No treatment needed
What is the most common clinical manifestation of Neisseria gonorrhoeae infection in neonates?
A. Pneumonia
B. Sepsis
C. Ophthalmitis
D. Meningitis
A 32-year-old adult presents with:
* Fever
* History of bloody diarrhea
* Now has pallor, edema, and decreased urine output
Question:
Which of the following is the most likely causative agent leading to this patient’s
current illness?
A. Escherichia coli 0157:H7
B. Shigella dysenteriae
C. Entamoeba histolytica
D. Campylobacter jejuni
Two playmates, ages 3 and 4, are brought to the emergency room with sudden onset of profuse, watery, voluminous stools. The stools are described as pale, odorless, and “rice water” in appearance. They are rapidly becoming dehydrated.
Question:
What is the most likely diagnosis?
A. Shigellosis
B. Rotavirus infection
C. Giardiasis
D. Cholera
What is the most common viral agent responsible for the common cold?
A. Coronavirus
B. Adenovirus
C. Rhinovirus
D. Respiratory syncytial virus (RSV)
An 8-year-old child presents with:
* High-grade fever for 5 days
* Cold extremities, rapid and weak pulse
* Petechial rash
* Narrow pulse pressure (<20 mmHg)
* Small pleural effusion detected on imaging
Question:
What is the most likely diagnosis?
A. Leptospirosis
B. Relapsing typhoid
C. Dengue Hemorrhagic Fever (DHF)
D. Rickettsial fever
A 3-year-old boy presents with:
* Fever for 1 week
* Tender cervical lymphadenopathy
* Foul-smelling breath (halitosis)
* Painful ulcers and lesions on the gums and lips
* Refuses to eat due to oral pain
Question:
What is the most likely diagnosis?
A. Aphthous stomatitis
B. Coxsackievirus (Hand-foot-mouth disease)
C. Herpangina
D. Herpes Simplex Virus (Primary Herpetic Gingivostomatitis)
A newborn develops sepsis and shock shortly after birth.
Question:
What is the most common causative pathogen responsible for systemic and focal infections (such as pneumonia, meningitis, and bacteremia) in neonates?
A. Escherichia coli
B. Listeria monocytogenes
C. Group B Streptococcus (GBS)
D. Klebsiella pneumoniae
A patient is brought to the clinic with:
* Headache
* Fatigue
On physical exam:
* Erythematous pharyngitis
* Generalized lymphadenopathy
* Hepatosplenomegaly
Question:
What is the most likely viral etiology for this presentation?
A. Cytomegalovirus (CMV)
B. Epstein-Barr Virus (EBV)
C. Parvovirus B19
D. Human Herpesvirus 6 (HHV-6)
What is the most common early symptom of AIDS in children and adults?
A. Gastrointestinal symptoms
B. Persistent skin rashes
C. Generalized lymphadenopathy
D. Fever and joint pain
Which of the following is currently the most important risk factor for acquiring HIV infection worldwide?
A. Perinatal transmission
B. Homosexual contact
C. Blood transfusion
D. Injection drug use
A 4-year-old child was diagnosed with uncomplicated measles. After a few days of improvement, the child develops persistent anorexia and fails to regain energy or appetite.
Question:
What is the most likely diagnosis explaining the persistent anorexia and delayed recovery?
A. Measles encephalitis
B. Secondary bacterial pneumonia
C. Reactivation of tuberculosis (TB)
D. Vitamin A deficiency
Which of the following is the most appropriate treatment for community-acquired pneumonia (CAP) caused by Chlamydia pneumoniae?
A. Amoxicillin
B. Ceftriaxone
C. Erythromycin
D. Vancomycin
Which of the following is NOT an important cause of occult bacteremia in previously healthy children?
A. Streptococcus pneumoniae
B. Haemophilus influenzae type B (Hib)
C. Neisseria meningitidis
D. Moraxella catarrhalis
What is the most common defined primary immunodeficiency disorder?
A. Common Variable Immunodeficiency (CVID)
B. Severe Combined Immunodeficiency (SCID)
C. Selective IgA Deficiency
D. X-linked Agammaglobulinemia (Bruton’s disease)
What are the major components of host defense mechanisms?
A. Only the adaptive immune system
B. Only the innate immune system
C. Anatomic barriers, innate immunity, and adaptive immunity
D. Antibodies and T-cells only
The adaptive immune system is primarily composed of which of the following immune cells?
A. Natural killer (NK) cells and macrophages
B. Neutrophils and monocytes
C. T cells and B cells
D. Eosinophils and basophils
Delayed separation of the umbilical cord after birth is most commonly associated with dysfunction of which immune component?
A. B lymphocytes
B. T lymphocytes
C. Complement system
D. Phagocytes
A 1-year-old child presents with recurrent infections, high fever, vomiting, lethargy, tonsillar atrophy, and absence of palpable lymph nodes.
Question:
What is the most likely diagnosis?
A. Common Variable Immunodeficiency (CVID)
B. Hyper-IgM Syndrome
C. Selective IgA Deficiency
D. X-linked Agammaglobulinemia (Bruton’s)
DiGeorge Syndrome (CATCH-22 / Velocardiofacial syndrome) includes all of the following features EXCEPT:
A. Congenital heart defects
B. Hypocalcemia
C. Cleft lip
D. Thymic hypoplasia
What is the recommended definitive treatment for Severe Combined Immunodeficiency (SCID)?
A. IV immunoglobulin therapy
B. Lifelong antibiotic prophylaxis
C. Hematopoietic stem cell transplantation (HSCT)
D. Gene therapy for all types
Which of the following is most characteristic of Chediak-Higashi Syndrome?
A. Increased neutrophil chemotaxis and opsonization
B. Hypergammaglobulinemia with eosinophilia
C. Giant cytoplasmic granules in neutrophils, partial albinism, and increased risk of malignancy
D. Defective Ig class-switching with normal lymphocyte counts
Deficiencies in the terminal components of the classical complement pathway (C5, C6, C8) are most strongly associated with which of the following conditions?
A. Recurrent pyogenic infections with encapsulated bacteria
B. Autoimmune hemolytic anemia
C. Disseminated meningococcal or gonococcal infections
D. Chronic granulomatous disease
Allergic asthma is an example of which type of hypersensitivity reaction?
A. Type I – Immediate (IgE-mediated)
B. Type II – Antibody-mediated cytotoxic
C. Type III – Immune complex-mediated
D. Type IV – Delayed-type (cell-mediated)
Serum sickness is an example of which type of hypersensitivity reaction?
A. Type I – IgE-mediated
B. Type II – Cytotoxic (antibody-mediated)
C. Type III – Immune complex-mediated
D. Type IV – Delayed-type (cell-mediated)
If one parent has an allergic condition (e.g., asthma, eczema, rhinitis), what is the approximate risk that the child will develop an allergic disease?
A. 10%
B. 25%
C. 50%
D. 75%
Which of the following is NOT a sign of moderate to severe airway obstruction due to an allergic response?
A. Nasal flaring
B. Use of accessory muscles
C. Retractions
D. Dennie-Morgan lines
Which of the following in vivo tests identifies allergen-specific IgE by introducing a small amount of allergen into the skin?
A. Patch test
B. Serum total IgE test
C. Intradermal test
D. Skin prick test
In IgE-mediated hypersensitivity testing, what is the expected time frame for a positive wheal-and-erythematous flare reaction to appear after the allergen is introduced into the skin?
A. 30 seconds
B. 5 minutes
C. 15–20 minutes
D. 24–48 hours
A child presents with multiple erosions and honey-colored crusts around the mouth and nose.
Question:
What is the most likely diagnosis?
A. Atopic dermatitis
B. Tinea corporis
C. Impetigo
D. Herpes simplex
Which of the following is NOT a major feature of atopic dermatitis in children?
A. Pruritus
B. Facial and extensor eczema
C. Chronic relapsing course
D. Angioedema
A 12-year-old child presents with sneezing, nasal congestion, clear nasal discharge, and nasal itching.
Question:
What is the most likely diagnosis?
A. Viral rhinitis
B. Allergic rhinitis
C. Sinusitis
D. Nasal polyps
In infants and young children, what is the most common food allergen associated with food-induced exacerbation of eczema?
A. Peanuts
B. Cow’s milk
C. Egg
D. Soy
- In infantile atopic dermatitis, which of the following areas is typically spared?
A. Face
B. Scalp
C. Extensor surfaces of arms and legs
D. Diaper area
- Which of the following findings would be least likely to be seen in a child with moderate to severe asthma?
A. Wheezing
B. Nasal flaring
C. Chest wall retractions
D. Clubbing
- Food allergies are the result of immune reactions to glycoproteins in genetically predisposed individuals.
Which of the following food items accounts for most severe allergic reactions?
A. Cow’s milk
B. Egg
C. Sweet peanuts
D. Peanuts
- Which of the following food allergies is least likely to be outgrown and most likely to persist into adulthood?
A. Cow’s milk
B. Egg
C. Soy
D. Shellfish
- As a medical student, you are asked to describe the type of lesion that initiates the process of acne in adolescents.
What is the primary lesion or initial event in all acne patients?
A. Pustule formation
B. Nodules
C. Microcomedone formation
D. Papule formation
- What is considered the first-line topical treatment for acne vulgaris, particularly in cases with comedonal lesions?
A. Oral antibiotics
B. Benzoyl peroxide alone
C. Topical corticosteroids
D. Topical retinoids
- A 16-year-old adolescent presents with severe nodulocystic acne that is painful, inflamed, and unresponsive to topical agents.
What is the most appropriate treatment?
A. Oral doxycycline
B. Topical retinoids and benzoyl peroxide
C. Oral isotretinoin
D. Oral contraceptive pills
- In the acute stage of dermatitis, which of the following is the most likely secondary lesion that may occur due to exudation from the inflamed skin?
A. Lichenification
B. Scarring
C. Hyperpigmentation
D. Weeping
- Seborrheic dermatitis is a chronic inflammatory disease that commonly affects sebaceous gland-rich areas of the body.
What is the classic location for seborrheic dermatitis in infants and adults?
A. Scalp
B. Hands
C. Lower legs
D. Abdomen
- Psoriasis is a common papulosquamous condition that may occur at all ages.
The most important, most common variety of psoriasis is:
A. Psoriasis vulgaris
B. Guttate psoriasis
C. Pustular psoriasis
D. Inverse psoriasis
Cutaneous hemangiomas may cause functional compromise depending on the location.
The area involved by hemangioma that most frequently poses a considerable risk and should be monitored carefully is:
A. Face
B. Back
C. Abdomen
D. Legs
Port wine stains are vascular malformations of the superficial capillaries of the skin.
Which of the following statements about port wine stains is accurate?
A. They do not enlarge after birth
B. They usually disappear spontaneously in childhood
C. They are associated with trigeminal neuralgia
D. They fade with time
A child presents with multiple discrete, flesh-colored, dome-shaped, smooth papules with a central umbilication.
What is the most likely diagnosis?
A. Verruca vulgaris (common warts)
B. Molluscum contagiosum
C. Seborrheic keratosis
D. Chickenpox
Pediculosis capitis may infect humans by visible manifestations indicating active infestation.
Which of the following are visible manifestations indicating active infestation?
A. Crusting
B. Excoriation
C. Lymphadenopathy
D. Brown nits
A 3-month-old infant develops otitis media and is given a course of clindamycin. A few days later, the infant develops extensive peeling of the skin. There are no mucosal lesions and the baby is not toxic.
What is the most likely diagnosis?
A. Toxic epidermal necrolysis (TEN)
B. Stevens-Johnson Syndrome (SJS)
C. Staphylococcal scalded skin syndrome (SSSS)
D. Drug-induced allergic reaction
What is the most common early symptom of AIDS in children and adults?
A. Gastrointestinal symptoms
B. Persistent skin rashes
C. Generalized lymphadenopathy
D. Fever and joint pain
Which of the following is currently the most important risk factor for acquiring HIV infection worldwide?
A. Perinatal transmission
B. Homosexual contact
C. Blood transfusion
D. Injection drug use
