Botulinum toxin-induced resolution of axillary granular parakeratosis

A 44-year-old woman presented with an 18-month history of a pruritic dermatitis in the axillae bilaterally, beginning in the springtime. There was no history of significant hyperhidrosis. The patient did not recall any change in deodorant, soap, detergent, or other topical products. Her family history was unremarkable for anyone with similar symptoms. Physical examination revealed hyperpigmented plaques on an erythematous base in both axillae. The inframammary and intertriginous folds were free of lesions. Histologic examination taken from the left axilla was notable for mild digitate papillomatosis, compact hyperparakeratosis with large nuclei, and retained keratohyaline granules within the stratum corneum (Figure), consistent with axillary granular parakeratosis. A periodic acid-Schiff stain was negative for hyphae. Patch testing utilizing the thin-layer rapid-use epicutaneous test (T.R.U.E. Test, Mekos Laboratories, Hillerod, Denmark) was unremarkable. The patient was initially treated with fluticasone propionate 0.05% cream without notable improvement. She then received Clostridium botulinum type A neurotoxin injections to the axillae (50 U/axilla) with complete resolution of the rash within a few days. At 6-months' follow-up, the patient remained asymptomatic.