Infectious Disease · Viral Exanthems
The facts most likely to be tested
Hand foot and mouth disease is most commonly caused by Coxsackievirus A16, a member of the Enterovirus genus.
The classic clinical presentation involves a vesicular rash on the palms and soles accompanied by oral enanthems.
Oral lesions typically manifest as painful vesicles and ulcers on the buccal mucosa, tongue, and hard palate.
Transmission occurs primarily through the fecal-oral route or via respiratory droplets.
The disease is most prevalent in children under 5 years of age and typically follows a self-limited clinical course.
Diagnosis is primarily clinical, based on the characteristic distribution of the rash and oral findings.
Management is supportive, focusing on hydration and pain control with acetaminophen or ibuprofen.
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A 3-year-old boy is brought to the clinic by his mother due to a 2-day history of fever and decreased oral intake. Physical examination reveals multiple painful vesicles on the tongue and buccal mucosa. Additionally, the child has a maculopapular and vesicular rash on the palms of his hands and the soles of his feet. The child is well-appearing, hydrated, and has no signs of meningeal irritation.
What is the most likely diagnosis?
Hand foot and mouth disease
The diagnosis is based on the classic distribution of vesicular lesions on the palms, soles, and oral mucosa, which is pathognomonic for this Coxsackievirus infection.
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Etiology / Epidemiology
Primarily affects children <5 years via fecal-oral or respiratory droplet transmission.
Clinical Manifestations
Presents with vesicular lesions on palms, soles, and oral mucosa; herpangina is a common variant.
Diagnosis
Diagnosis is clinical; viral culture or PCR of vesicle fluid is the gold standard if needed.
Treatment
Management is supportive with hydration and analgesia; avoid aspirin due to Reye syndrome risk.
Prognosis
Self-limiting condition; 10 days is the typical duration for full resolution.
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Epidemiology & Etiology
Caused by Coxsackievirus A16 or Enterovirus 71. Highly contagious, peaking in summer and fall. Outbreaks are common in daycare settings and schools.
Pertinent Anatomy
Involves the oral mucosa (buccal, tongue, palate) and the distal extremities (palms and soles). The virus exhibits specific tropism for the epithelium of these regions.
Pathophysiology
Viral entry occurs via the GI tract, followed by replication in the pharynx and regional lymph nodes. Viremia leads to systemic dissemination to the skin and mucous membranes. The immune response causes the characteristic vesicular eruption.
Clinical Manifestations
Initial symptoms include fever and malaise, followed by painful oral ulcers. Classic exanthem consists of grayish-white vesicles on an erythematous base. Red flags include signs of aseptic meningitis or encephalitis (e.g., nuchal rigidity, altered mental status).
Diagnosis
Diagnosis is primarily clinical based on the distribution of lesions. Viral culture or RT-PCR from throat swabs or vesicle fluid is the gold standard for definitive identification. No specific laboratory threshold is required for diagnosis.
Treatment
Treatment is supportive care focusing on hydration and pain control with acetaminophen or ibuprofen. Aspirin is strictly contraindicated in children. Encourage fluid intake to prevent dehydration.
Prognosis
The disease is self-limiting and typically resolves within 7-10 days. Rare complications include aseptic meningitis, encephalitis, or onychomadesis (nail shedding) weeks after infection.
Differential Diagnosis
Herpangina: lesions limited to the posterior oropharynx
Herpetic gingivostomatitis: lesions involve the anterior mouth and gingiva
Erythema multiforme: targetoid lesions, usually drug-induced
Varicella: lesions in various stages of development (dewdrop on a rose petal)
Stevens-Johnson Syndrome: severe mucosal involvement with systemic toxicity