Distinguishing annular pustular psoriasis from subcorneal pustular dermatosis-A diagnostic dilemma in a 10-year-old boy.

Subcorneal pustular dermatosis (SPD) and annular pustular psoriasis (APP) are very rare in childhood and difficult to differentiate both clinically and histopathologically. We report the case of a 10-year-old male with a 9-year history of erythematous scaly annular plaques with scattered pustules on the trunk. Although initially diagnosed as SPD, a lack of response to dapsone, presence of spongiosis on histology, and early age of disease onset led to consideration of APP. The patient was subsequently treated with adalimumab 80 mg weekly and completely cleared. This case illustrates the overlapping features of SPD and APP and suggests that the two disorders may represent a spectrum of the same disease.