Aseptic and alopecic nodules of the scalp (AANS), previously known as pseudocysts of the scalp, is a rare, acquired condition where skin-colored, nontender, dome-shaped nodules with overlying nonscarring alopecia appear on the scalp.

AANS predominantly affects young males between 20 and 30 years of age. The nodules are firm or fluctuant and most are asymptomatic, but patients may have mild pruritus, pain, or discomfort. Nodules vary in size from 1.5-3 cm.

The etiology of AANS has not been studied. The current hypothesis suggests that nodule formation may be attributed to an immunological-driven granulomatous reaction to a foreign body or follicular disruption that occludes the follicle. The granulomatous infiltrate is located deep in the hair follicle and is likely responsible for nonscarring alopecia.