Diagnosis: Hand, Foot, and Mouth Disease (HFMD)
The most likely diagnosis is hand, foot, and mouth disease (HFMD), a viral exanthem caused primarily by Coxsackievirus A16, Coxsackievirus A6, or Enterovirus 71, characterized by fever, sore throat, and papular/vesicular lesions on the oral mucosa (inner cheeks, palate, pharynx). 1, 2
Key Diagnostic Features
Classic Presentation
- Fever accompanied by painful papules, vesicles, or ulcerations inside the mouth (buccal mucosa, palate, pharynx) is the hallmark of HFMD 1, 3
- Oral lesions typically appear first, often before skin manifestations develop on the hands, feet, or buttocks 3
- The enanthem involves vesiculation and ulceration of the mouth, palate, and pharynx, causing significant sore throat and odynophagia 1
Atypical Presentations (Coxsackievirus A6)
- Since 2008–2011, Coxsackievirus A6 has caused more extensive disease with widespread vesiculobullous eruptions extending beyond the classic hand-foot-mouth distribution 4, 2
- Peri-oral rash is strongly associated with CV-A6 (P < 0.001) 2
- Generalized exanthema involving 5 or more anatomical sites (hands, feet, mouth, buttocks, legs, arms, trunk) occurs in 41.5% of confirmed cases 2
- High fever and vesiculobullous eruptions on the calves and backs of hands characterize the atypical CV-A6 variant 4
Differentiating HFMD from Other Causes
Why Not Herpes Simplex Virus (HSV)?
- HSV-1 causes gingivostomatitis with gingival inflammation and bleeding, not isolated papules on the buccal mucosa 5
- HSV labialis primarily affects the lips and perioral skin, not intraoral surfaces 5
- HSV does not typically produce the hand-foot distribution seen in HFMD 3
Why Not Group A Streptococcus (Scarlet Fever)?
- Scarlet fever presents with a sandpaper-like rash on the trunk and extremities, not vesicular oral lesions 6
- The pharyngitis in scarlet fever shows tonsillopharyngeal erythema with exudates and palatal petechiae, not discrete papules or vesicles on the buccal mucosa 6
- Microbiological confirmation (RADT or throat culture) is required to diagnose GAS pharyngitis; clinical features alone are insufficient 7, 8
Why Not Other Viral Pharyngitis?
- Adenovirus, rhinovirus, and respiratory syncytial virus cause pharyngitis with prominent upper respiratory symptoms (cough, rhinorrhea, hoarseness, conjunctivitis) 7, 9
- These viruses do not produce the characteristic vesicular oral lesions seen in HFMD 7
Diagnostic Confirmation
- Clinical diagnosis is usually sufficient when the classic triad of fever, oral vesicles/ulcers, and hand-foot lesions is present 1, 3
- PCR of vesicular swabs or stool samples can confirm enterovirus infection and identify the specific serotype (CV-A6, CV-A16, EV-71) 4, 2
- Laboratory testing is not routinely necessary unless the presentation is atypical or severe neurological complications are suspected 1
Management
- Treatment is palliative only: analgesics (acetaminophen or ibuprofen, avoiding aspirin in children), adequate hydration, topical oral anesthetics (lidocaine gel), and soft diet 3, 7
- Antibiotics are not indicated for HFMD; this is a self-limiting viral illness 7
- Symptoms typically resolve within 7–10 days without complications 3, 4
- Onychomadesis (nail shedding) may occur 4–6 weeks after infection, particularly with CV-A6 4, 1
Common Pitfalls
- Do not mistake HFMD for bacterial pharyngitis and prescribe unnecessary antibiotics; the presence of oral vesicles/papules strongly favors a viral etiology 7
- Do not overlook Enterovirus 71 in endemic areas (Asia), which can cause severe neurological complications including encephalitis, aseptic meningitis, and acute flaccid paralysis 1, 5
- Recognize that CV-A6 can cause extensive disease that may initially be mistaken for varicella, eczema herpeticum, or Stevens-Johnson syndrome 4, 1
- Transmission occurs via fecal-oral route and respiratory droplets; household contacts (including adults) are at risk 1