Blistering rash in a 1-year-old boy
A 1-year-old boy presents with a diffuse rash on the body for the past 3 days (Figures 1 and 2). The rash started on his hands, then progressed to include his face, trunk, buttocks, groin, legs and feet. He also developed low-grade fevers and increased fussiness. He has a history of atopic dermatitis that has been difficult to control with hydrocortisone 2.5% ointment. He attends a day care center three times a week.
Can you spot the rash?
A. Varicella
B. Eczema herpeticum
C. Bullous impetigo
D. Eczema coxsackium
E. Scabies
Case Discussion
Hand-foot-and-mouth disease (HFMD) is a common viral exanthem caused by nonpolio enteroviruses. Transmission of the virus occurs via the fecal-oral route. It is extremely contagious, and outbreaks are seen in day care centers and schools. Peak activity of the virus is usually seen in the summer and fall, although newer strains of coxsackievirus tend to defy seasonality. It most commonly affects children from age 1 year to preschool age.
Classically, HFMD presents with erythematous macules, papules and oval gray-white vesicles on the palms, soles, and oral mucosa. The rash may be accompanied by fever, fussiness, diarrhea and/or cervical and submandibular lymphadenopathy. Oral lesions are often painful and can result in decreased intake of food and water. Resolution of the rash can be followed a few weeks later with shedding of the nails, known as onychomadesis, which regrow over time.
Although Coxsackie A16 virus is responsible for most cases of classic HFMD, Coxsackie A6 virus causes atypical HFMD. This variant presents with the classic HFMD lesions, along with an exuberant eruption composed of vesicles and erosions accentuated on the perioral region, extremities, groin and buttocks. When the lesions concentrate in areas of eczema, the diagnosis has been coined “eczema coxsackium” (correct choice — D). Depending on the severity of the underlying eczema, the blistering lesions can become quite widespread.
Children with eczema are at risk for superinfection given the combination of impaired barrier function and immune dysregulation in the skin. Thus, the differential diagnosis of a blistering and erosive rash in a child with eczema should always include other infectious etiologies such as herpes simplex virus, varicella and bullous impetigo. These entities may be difficult to distinguish from one another and from enterovirus infection, so it is important to test the vesicle fluid with a bacterial culture and viral PCRs for varicella, HSV and enterovirus if the diagnosis is not clear. If a fresh vesicle is not present, viral PCRs can be taken from the oropharynx, where enterovirus can remain present for up to 2 weeks after infection, or the perianal region, where the virus may be shed up to 6 weeks later. Some clinical clues that can help differentiate eczema coxsackium from eczema herpeticum include abrupt onset, acral and symmetric distribution and lack of punched-out erosions. Scabies can also present with pruritic, scaling papules and eczematous lesions concentrated on palms and soles. However, scabies tends to start more insidiously and is not accompanied by systemic symptoms or oral erosions.
All forms of HFMD are self-limited and resolve without therapy. Treatment is largely supportive. Although the rash usually resolves within 1 week, children are often still infectious because of persistent viral shedding in the stool. In eczema coxsackium, it may be helpful to treat the underlying dermatitis with a mild-potency topical steroid. Complications are very rare but can include aseptic meningitis, encephalitis and myocarditis.
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