Amicrobial pustulosis of the folds: Report of 4 cases.

Amicrobial pustulosis of the folds (APF) is a rare disease characterized by aseptic pustular lesions involving cutaneous folds, typically occurring in the context of an autoimmune disorder. We present 4 patients with APF, focusing on clinical and histopathologic characteristics to improve the recognition of this entity. All 4 patients had intertriginous and extra-intertriginous involvement. Common histopathologic features of skin biopsies in these patients were intracorneal, subcorneal, intraepidermal, perivascular, perifollicular and interstitial neutrophilic inflammation. Pustules overlying adnexal ostium and papillary dermal edema were consistently observed. The pustules were negative for microorganisms on stain testing. In these cases, associated conditions were undifferentiated connective tissue disease, systemic lupus erythematosus, antiphospholipid syndrome, Crohn disease and Hashimoto thyroiditis. The aforementioned clinical and histopathologic characteristics of patients with suspected or diagnosed connective tissue disorders should lead to suspicion for APF.