An under-recognized clinical and histopathological condition

Abstract

Conflict of interest: none declared. A 38‐year‐old woman presented with a unilateral left axillary lesion that had been present for 3–4 years. The patient was otherwise well with no previous skin conditions. She was not on medication and had no relevant family history. There had been no response to moderate‐strength topical steroids or to oral doxycycline. Treatment with topical calcipotriene cream had cleared the lesion but on cessation of the treatment, the lesion recurred. On physical examination, a superficially eroded, erythematous plaque was noted (Fig. 1a,b). The differential diagnosis included acanthosis nigricans, pemphigus vegetans, Hailey–Hailey disease and inverse psoriasis. ... On histopathological examination, the stratum corneum was found to be thickened, with parakeratosis and prominent keratohyaline granules visible (Fig. 2). The underlying epidermis was hyperplasic with some papillomatosis. There were no fungal elements on periodic‐acid–Schiff stain. ... What is your diagnosis? Granular parakeratosis (GP).