Eccrine hidradenitis sine neutrophils: a toxic response to chemotherapy

We present a case of hidradenitis occurring in a patient after chemotherapy for acute myeloid leukemia (AML) in the setting of profound neutropenia. Neutrophilic eccrine hidradenitis (NEH) presents as tender erythematous papules and plaques and is often associated with chemotherapy for AML. NEH is postulated to be due to toxic injury to the sweat glands followed by neutrophilic inflammation. Alternatively, some hypothesize that NEH represents a primary neutrophilic process. Our patient's clinical presentation was similar to previously reported cases of NEH; however, degenerative changes of the sweat ducts were noted on microscopy without neutrophilic inflammation. She had fewer than 0.01 thousand neutrophils per microliter for 4 days preceding the biopsy. At the same time, a separate area of superficial skin infection developed because of Staphylococcus epidermidis and also lacked neutrophilic inflammation. The similar clinical course and shared histopathologic features between our case and NEH argue that neutrophils are a secondary response to a toxic effect rather than the primary effector in NEH. Neutrophil-poor variants of hidradenitis, both infectious and due to drug toxicity, should be considered diagnostically in neutropenic patients.