Hand, Foot and Mouth Disease
Hand, foot and mouth disease (HFMD) is an acute infection caused by viruses of the genus Enterovirus (family Picornaviridae). Coxsackievirus A16 (CVA16) and enterovirus 71 (EV71) are the two classic culprits, but recent outbreaks show a sharp rise in coxsackievirus A6 (CVA6), which causes atypical presentations, widespread skin lesions and delayed nail shedding (onychomadesis).
The infection spreads mainly by the fecal–oral route and through direct contact with respiratory secretions, blister fluid or droplets. After entering through the throat or gut lining, the virus multiplies in regional lymph nodes, causes a secondary viremia and then settles in the skin and mucous membranes.
Viral Causes and Pathogenesis
Causative Viruses
- Coxsackievirus A16 (CVA16): the most common cause of the typical mild form. Skin and mouth lesions are self-limiting and neurological complications are rare.
- Enterovirus 71 (EV71): the most neurotropic strain. EV71 can reach the central nervous system via peripheral nerves, causing encephalitis, brainstem encephalitis, acute pulmonary edema and sudden circulatory failure.
- Coxsackievirus A6 (CVA6): causes "atypical" HFMD. The rash is extensive, with large bullous blisters spreading beyond the usual sites (face, arms, thighs), and it can cause late complications 2–6 weeks later such as Beau's lines or nail shedding (onychomadesis).
Recognizing the Disease and Its Time Course
- Incubation period: 3–7 days, with no symptoms at all.
- Prodrome (1–2 days): low-grade fever (37.5–38.5 °C), sore throat, drooling, poor appetite and mild diarrhea.
- Full-blown stage (3–10 days): mouth lesions (enanthem) and skin lesions (exanthem) erupt together.
Clinical Features
Mouth Lesions (Enanthem):
- Location: inner cheeks, gums, tongue and soft palate.
- Appearance: small 1–2 mm blisters on a red base that break quickly into shallow ulcers with a yellow-gray base and red rim.
- Symptoms: intense burning pain, so children refuse food, cannot swallow their saliva (constant drooling) and are fretful.
Skin Lesions (Exanthem):
- Classic sites: palms, soles, knees, buttocks and the diaper area.
- Appearance: oval, rice-grain-shaped blisters 2–10 mm across, raised or sitting just under the skin, not painful to touch or press, filled with clear fluid that later turns cloudy.
- Course: the blisters rarely burst as they fade; they dry into brownish marks and do not scar unless a bacterial infection sets in.
Differential Diagnosis of Acute Blistering Rashes
| Hand, Foot and Mouth Disease (Coxsackievirus A) | Chickenpox (Varicella Zoster Virus) | Herpetic Gingivostomatitis (HSV-1) |
|---|---|---|
| Palms, soles, buttocks, knees, inside the mouth | Widespread over the body, mostly head, face and trunk | Only around the mouth, lips and gums |
| Oval, painless to the touch, not itchy | Lesions at different stages at the same time (red spots, blisters, pustules, crusts) | Clustered blisters that break easily and crust |
| Shallow ulcers on the cheeks, tongue and palate | Scattered blisters that break into mucosal ulcers | Fiery red, swollen gums that bleed easily |
| Nail shedding (CVA6), neurological complications (EV71) | Staphylococcal superinfection, pitted scars | Recurrent infection, scarring |
Clinical Grading and Warning Signs
By medical standards, spotting early signs that the illness is progressing (from grade 1 to grade 2) can be lifesaving:
- Grade 1 (mild, managed at home): skin lesions and/or mouth ulcers only.
- Grade 2a (warning of progression, needs close monitoring):
- Startle jerks with flailing arms 1–2 times in 30 minutes (not observed during deep sleep).
- High fever above 39.0 °C that will not come down, or fever lasting more than 2 days.
- Lethargy, unexplained crying, drowsiness.
- Grades 2b–4 (severe, urgent hospital admission):
- Grade 2b: startle jerks more than 3 times in 30 minutes, ataxia (unsteady walking), nystagmus, limb weakness or tremor.
- Grade 3: high blood pressure, heart rate above 170 beats/min, cold sweats, rapid or shallow breathing.
- Grade 4: neurogenic shock, acute pulmonary edema, cyanosis, respiratory arrest.
Management and Care at Haute-Derma
Fever and Pain Control at Home
- Fever and pain relief: paracetamol 10–15 mg/kg per dose, by mouth every 4–6 hours, not exceeding 60 mg/kg in 24 hours. Note: avoid ibuprofen if dehydration is suspected or dengue fever has not been ruled out.
- Easing mouth ulcer pain:
- Apply a 0.2% hyaluronic acid gel or a film-forming oral gel 15 minutes before meals to shield the ulcers and make eating easier.
- Offer soft, cool, liquid foods (cooled rice porridge, chilled milk, avocado) and avoid sour, salty or hot foods that sting.
Skin Lesion Care and Antisepsis
- Surface antisepsis: dab gentle, non-stinging antiseptics such as nano-silver, octenidine dihydrochloride or 1% methylene blue on broken blisters to prevent bacterial superinfection (Staphylococcus aureus).
- Moisturizing and repair: once the lesions start drying, a moisturizer with ceramides and zinc oxide helps the skin barrier recover quickly.
- Managing nail shedding (onychomadesis from CVA6): we reassure parents that nail shedding 2–6 weeks after the illness is a natural, non-infectious process. Keep the nails trimmed short and moisturize the nail folds; new nails grow back completely normally within 3–6 months.
