Dermatology MCQ - Viral Infections - Varicella

A 4-year-old child presents with a generalized pruritic rash that started on the face and trunk before spreading to the extremities. The rash consists of erythematous macules, papules, vesicles, and crusted lesions in various stages of evolution. The child has a low-grade fever and mild malaise. The mother reports that several other children at the daycare have had similar symptoms. Which of the following is the most likely route of transmission and the site of viral latency for this infection?

A) Respiratory droplets; latency in dorsal root ganglia
B) Direct contact with skin lesions; latency in trigeminal ganglia
C) Fecal-oral route; latency in sacral ganglia
D) Blood transfusion; latency in bone marrow
E) Sexual contact; latency in sensory nerve endings

Correct Answer: A) Respiratory droplets; latency in dorsal root ganglia.

Explanation

This presentation is classic for varicella (chickenpox), caused by the varicella-zoster virus (VZV).

Key Clinical Features of Varicella:

• Rash Description: The rash is pruritic and appears in crops, leading to the simultaneous presence of macules, papules, vesicles, and crusts ("dew drops on a rose petal"). It typically starts on the face and trunk (centripetal distribution) before spreading to the extremities.

• Systemic Symptoms: Low-grade fever, malaise, and headache are common.

• Epidemiology: Highly contagious, with outbreaks common in settings like daycares and schools.

Virologic Features:

• Transmission: Primarily through respiratory droplets from infected individuals. The virus can also be transmitted via direct contact with vesicular fluid.

• Latency: After primary infection (chickenpox), VZV establishes lifelong latency in the dorsal root ganglia (and occasionally cranial nerve ganglia).

• Reactivation: Later in life, reactivation of VZV causes herpes zoster (shingles), characterized by a painful dermatomal vesicular rash.

Why Not the Other Options?

• (B) Direct contact; latency in trigeminal ganglia: While direct contact can transmit VZV, the primary route is respiratory. Latency occurs in dorsal root ganglia, not specifically trigeminal ganglia (though cranial nerves can be affected).

• (C) Fecal-oral route; latency in sacral ganglia: This describes enteroviruses (e.g., coxsackievirus), which cause hand, foot, and mouth disease, not varicella.

• (D) Blood transfusion; latency in bone marrow: VZV is not typically transmitted via blood transfusion. Latency occurs in neural ganglia, not bone marrow.

• (E) Sexual contact; latency in sensory nerve endings: This describes herpes simplex virus (HSV), which causes genital or oral herpes and establishes latency in sensory ganglia (e.g., trigeminal or sacral).

Management:

• Supportive care: Antihistamines for pruritus, acetaminophen for fever (avoid aspirin due to Reye's syndrome risk), and calamine lotion.

• Antivirals: Oral acyclovir or valacyclovir may be used in high-risk patients (immunocompromised, adolescents, adults) if started early.

• Prevention: Vaccination with the live attenuated varicella vaccine.

Complications:

• Bacterial superinfection of skin lesions (e.g., Staphylococcus aureus).

• Pneumonia, encephalitis (more common in adults and immunocompromised individuals).

• Reactivation as herpes zoster later in life.

Prognosis:
Generally excellent in healthy children, with resolution within 7–10 days.