Axillary Granular Parakeratosis.

We describe a case of an 85-year-old Caucasian female who presented to the dermatology clinic with pruritic, scaly hyperpigmented papules and plaques with surrounding erythema in the left axilla. Based on the history and physical examination, there was concern for possible varicella zoster infection, and the patient was started on valacyclovir 1000 mg three times daily for seven days. A shave biopsy was taken from the left axilla to confirm a diagnosis. Microscopic examination revealed compact hyperparakeratosis with keratohyalin granules throughout the parakeratotic stratum corneum as well as admixed eosinophils within the stratum corneum. The epidermis was acanthotic with irregular hyperplasia of the rete ridges. These microscopic findings supported a diagnosis of axillary granular parakeratosis, a benign skin condition caused by a defect in epidermal differentiation. Granular parakeratosis is seemingly rare but is felt to be an underreported condition. It is important for clinicians to be aware of the disease in order to correctly identify the lesions and reassure patients of its benign nature and provide appropriate treatment recommendations.