Hand, Foot, and Mouth Disease (HFMD)

Introduction

Hand, Foot, and Mouth Disease (HFMD) is an acute, highly contagious viral illness predominantly affecting infants and young children. It is characterized by febrile illness, oral mucosal lesions, and a distinctive maculopapular or vesicular rash on the hands, feet, and often buttocks. While the majority of cases are self-limited, severe and occasionally fatal complications can occur, particularly with certain enterovirus serotypes such as EV71.

Etiology and Epidemiology

• Causative Agents: Primarily enteroviruses—Coxsackievirus A16 (CoxA16) and Enterovirus 71 (EV71). Other serotypes (CoxA4, A6, A10, Echoviruses) have been implicated in outbreaks.
• Transmission:
• Fecal–Oral Route: Viral shedding in stool for up to 3–5 weeks.
• Respiratory Droplets: Secretions from the oropharynx for 1–2 weeks.
• Direct Contact: Vesicle fluid, fomites (toys, utensils, bedding).
• Reservoir: Humans (symptomatic and asymptomatic carriers).
• Seasonality and Outbreaks: Year-round in tropical climates, with peaks in spring–summer in temperate zones. Epidemic spread is common in childcare settings.
• At-Risk Population: Children under 5 years; 85–95% of cases occur in those <4 years old. Immunity following infection is serotype-specific and of uncertain duration.

Pathogenesis

Enteroviruses infect the oropharyngeal and intestinal mucosa, replicate in local lymphoid tissue, and disseminate via the bloodstream (viremia). Viral tropism for skin and mucosal cells results in characteristic lesions. Neurotropic strains (e.g., EV71) can invade the central nervous system, causing severe neurological sequelae.

Clinical Presentation

Incubation Period

Typically 3–6 days (range: 2–10 days).

Prodrome

• Low-grade fever, malaise, anorexia, irritability, and upper respiratory symptoms (cough, rhinorrhea).

Mucocutaneous Manifestations

• Oral Lesions: Painful herpangina-like vesicles and ulcers on buccal mucosa, tongue, and soft palate; may interfere with oral intake.
• Cutaneous Rash: Maculopapular or vesicular lesions with an erythematous halo on the dorsal hands (particularly the fingertips), plantar feet, and buttocks. Lesions may coalesce and vary in size (2–10 mm).
• Distribution: Less commonly on the trunk, elbows, knees.

Severe and Complicated Disease

While most HFMD cases resolve within 7–10 days, watch for red flags:
1. Neurological Involvement: Irritability, lethargy, myoclonus, ataxia, seizures—suggests meningitis, encephalitis, or brainstem encephalitis (EV71).
2. Cardiopulmonary Failure: Dyspnea, tachypnea, pulmonary edema, and shock due to neurogenic or cardiogenic mechanisms.
3. Circulatory Collapse: Cold extremities, prolonged capillary refill, hypotension, tachycardia or bradycardia.
4. Metabolic Abnormalities: Hyperglycemia, leukocytosis, thrombocytopenia.

Diagnosis

• Clinical Diagnosis: Based on characteristic rash and mucosal lesions in pediatric patients.
• Laboratory Testing (selective):
• Viral Detection: Throat swab or stool PCR for enterovirus serotyping; reserved for severe or atypical cases.
• CSF Analysis: In suspected CNS involvement—lymphocytic pleocytosis.
• Blood Work: CBC, glucose, liver enzymes, CRP/ESR for systemic involvement.

Differential Diagnosis

• Herpangina (isolated oral lesions)
• Varicella (dew-drop vesicles on erythematous base, centripetal distribution)
• Herpes simplex (grouped vesicles, perioral distribution)
• Erythema multiforme (target lesions on acral surfaces)
• Atypical rash from enteroviral or other viral infections

Management

Supportive Care (Mainstay)

• Hydration and Nutrition: Encourage frequent small feeds, oral rehydration solutions. Monitor intake in infants and young children.
• Antipyretics and Analgesics: Acetaminophen or ibuprofen for fever and pain control.
• Topical Treatments: Viscous lidocaine or diphenhydramine mouthwash for oral ulcers; calamine lotion for pruritic rash.

Specific Interventions

• Hospitalization Criteria: Dehydration, inability to tolerate oral intake, neurological signs, cardiorespiratory instability.
• Intravenous Fluids: For intractable vomiting or dehydration.
• Monitoring: Neurological status, respiratory rate, heart rate, capillary refill.

Prevention and Public Health Measures

• Infection Control: Strict hand hygiene, environmental disinfection, cohorting in outbreaks.
• Exclusion Policies: Keep symptomatic children out of daycare until fever-free for 24 hours and lesions are crusted or resolved.
• Vaccine Development: EV71 vaccines licensed in China; no universal immunization currently recommended.

Prognosis

• Uncomplicated HFMD: Recovery within 1–2 weeks without sequelae.
• Severe HFMD: Mortality rates <0.5% but higher in outbreaks caused by EV71; survivors may have neurological sequelae.
• Follow-Up: Reassess neurological function and developmental milestones in children with severe disease.

Conclusion

HFMD is a common pediatric viral illness with a characteristic clinical presentation. While most cases are benign, prompt recognition of severe disease markers and supportive management are essential to reduce morbidity and mortality. Ongoing public health efforts and vaccine development aim to further mitigate the impact of HFMD in endemic regions.