Dermatology MCQ - Viral Infections - Hand, foot and mouth disease

A 4-year-old child presents with fever, oral vesicles and ulcers, and vesicular lesions on the palms and soles. The child's parents report that several other children at the daycare have similar symptoms, and there is a known outbreak in the community. The child is irritable due to mouth pain but is otherwise hydrated and alert. Which of the following is the most likely causative agent and its primary mode of transmission?

A) Coxsackievirus A16; fecal-oral route
B) Varicella-zoster virus; respiratory droplets
C) Herpes simplex virus type 1; direct contact
D) Measles virus; airborne transmission
E) Staphylococcus aureus; contact with fomites

Correct Answer: A) Coxsackievirus A16; fecal-oral route

Explanation

This presentation is classic for hand, foot, and mouth disease (HFMD), a common viral illness in children, often caused by coxsackievirus A16.

Key Clinical Features of Hand, Foot, and Mouth Disease:

• Fever: Often low-grade, preceding the rash.

• Oral Lesions: Painful vesicles and ulcers on the tongue, gums, and inside cheeks.

• Cutaneous Lesions: Vesicles on the palms, soles, and sometimes buttocks. The vesicles are often tender and may rupture or form crusts.

• Other Symptoms: Irritability, decreased appetite due to oral pain.

• Epidemiology: Highly contagious; outbreaks common in daycares and schools.

Virologic Features:

• Causative Agents: Most commonly coxsackievirus A16 (enterovirus family). Other enteroviruses (e.g., enterovirus 71) can cause more severe disease.

• Transmission: Fecal-oral route is primary; also respiratory droplets and contact with vesicle fluid or fomites.

Why Not the Other Options?

• (B) Varicella-zoster virus: Causes chickenpox with a generalized vesicular rash (centripetal distribution), not localized to hands/feet/mouth.

• (C) Herpes simplex virus type 1: Causes herpetic gingivostomatitis with oral vesicles/ulcers but typically no lesions on palms/soles.

• (D) Measles virus: Causes measles with Koplik spots and a maculopapular rash (cephalocaudal spread), not vesicles.

• (E) Staphylococcus aureus: Causes impetigo (honey-crusted lesions) or bullous impetigo, not oral and acral vesicles.

Management:

• Supportive care: Hydration, soft foods, analgesics (e.g., acetaminophen) for pain.

• Infection control: Hand hygiene, avoid sharing utensils/toys.

Prognosis:
Self-limiting; resolves in 7-10 days. Rare complications include aseptic meningitis or nail changes (onychomadesis weeks later).

Note: HFMD is often confused with foot-and-mouth disease (hoof-and-mouth disease), which affects livestock and is caused by a different virus (apthovirus). HFMD is a human-specific enteroviral infection.