Plaques and erosions around orifices and acral regions in an infant

A 7-month-old male who had been born prematurely presents with a 2-month history of diarrhea, failure to thrive, alopecia, and rash involving the perioral, perianal, and acral areas. He had been treated unsuccessfully for presumed atopic dermatitis with topical corticosteroids. He was exclusively breastfed until 2 months ago, when he was transitioned to formula. Examination reveals an irritable, thin infant ...