Granular Parakeratosis: Response to Calcipotriene and Brief Review of Current Therapeutic Options

A 34-year-old Hispanic woman presented with an 18-month history of an intermittent, asymptomatic eruption that began on her left axilla after using a depilatory cream containing corn starch and thioglycolate (Figure 1A). The eruption then spread to her right axilla and lower abdomen (Figure 1B). She reported worsening with deodorant use, but had been using the same deodorant for many years and had continued using it twice a day. Treatment with topical corticosteroids had not helped. The patient coincidentally had been started on isotretinoin 5 months previously for acne, but it had no effect on her axillary or abdominal lesions. Physical examination revealed multiple dark brown and black papules with a "stuck-on" appearance in both axillae and on the lower right abdomen. A biopsy of the left axilla revealed a thickened parakeratotic stratum corneum with retention of keratohyalin granules within the parakeratoric cells, which is considered diagnostic of granular parakeratosis (Figure 2). The patient was prescribed calcipotriene cream twice daily. After 2 weeks, she had complete resolution of the axillary lesions, but the abdominal lesions persisted. She has since had mild recurrences while using calcipotriene.