What Is Your Diagnosis? Axillary Granular Parakeratosis

A 52-year-old obese woman presented with dark brown, scaly, nontender, and nonpruritic eruptions in both axillae that gradually had enlarged and thickened in the last 6 weeks. The left axilla (left) appeared to be more affected than the right axilla (right). The lesions initially appeared as hyperpigmented papules that coalesced into dark plaques covered by an adherent, keratotic, friable scale. Her medical history was notable for mild asthma, seasonal allergies, and obesity. She denied any history of diabetes mellitus. There was no other intertriginous involvement. Potassium hydroxide preparation of the lesion was negative for fungi.