Body-wide, pruritic, papular rash • scalp lesion • excoriation • Dx?

THE DIAGNOSIS

The answer is C, dermatophytid reaction.

DISCUSSION

A dermatophytid reaction is a type of id reaction, or autoeczematization. An id reaction is when a localized dermatitis becomes a generalized pruritic eruption.¹ In this case, the patient’s dermatitis was the result of a dermatophyte infection (tinea capitis), but an id reaction can also occur in response to noninfectious dermatitides and may be of an atopic, contact, or seborrheic nature.¹

Dermatophytid reactions occur in up to 5% of all dermatophyte infections (most commonly tinea pedis) and are proposed to be type IV hypersensitivity reactions to the release of fungal antigens.¹ These reactions can occur either before or after the initiation of antifungal treatment. They manifest as symmetric, pruritic, papulovesicular eruptions with fine scaling and commonly affect the face, trunk, extremities, palms, and interdigital spaces.¹

What about other possible diagnoses?

Gianotti-Crosti syndrome is an asymptomatic, symmetric, papulovesicular dermatosis that involves the face, limbs, and buttocks of children 2 to 6 years of age.² The lesions develop in response to a respiratory or gastrointestinal illness.² They are typically associated with Epstein-Barr virus, hepatitis B, cytomegalovirus, respiratory syncytial virus, and coxsackievirus, but can occur with bacterial infections or following administration of routine immunizations.²

While the initial impulse may be to discontinue oral antifungals, these treatments help resolve the underlying dermatophyte infection and should be continued.

The lesions are self-limited and resolve within 2 months.² Symptomatic lesions may be treated with oral antihistamines or steroids (topical or systemic).²

Continue to: Atopic dermatitis