A woman in her 20s was seen with a 6-year history of recurrent, pruritic skin eruptions involving the middle and lower back. Before evaluation in our department, the patient had undergone a skin biopsy that showed spongiotic dermatitis, had patch testing that was reportedly negative, and received a diagnosis of atopic dermatitis. She was treated with potent topical corticosteroids and oral prednisone, with no improvement. She denied use of heating pads, space heaters, or other forms of external radiation. Physical examination showed several discrete, erythematous, scaly papules admixed with light brown reticulated macules and patches (Figure , A and B). Punch biopsy specimens were obtained for further evaluation (Figure, C and D). A Light brown macules and patches Punch biopsy specimen C Punch biopsy specimen D B Scaly papules and hyperpigmented patches Figure. A, Light brown macules and patches on the back show a strikingly reticular pattern. B, Discrete erythematous and scaly papules and overlying hyperpigmented patches are shown. C, Histopathologic examination shows eosinophilic spongiosis with interface dermatitis, dyskeratosis, and neutrophilic exocytosis (hematoxylin-eosin, original magnification ×20). D, Prominent dermal melanophages are present (hematoxylin-eosin, original magnification ×20). WHAT IS YOUR DIAGNOSIS? A. Erythema ab igne B. Prurigo pigmentosa C. Dowling-Degos disease D. Confluent and reticulated papillomatosis Clinical Review & Education