Concomitance of psoriasis and atopic dermatitis.

There is a widespread belief that psoriasis (Ps) and atopic dermatitis (AD) are clinically mutually exclusive. A prospective study was undertaken to record the concurrent and/or consecutive coincidence of the two conditions and any shared clinical features. Patients attending a dermatology clinic were systematically examined for the presence of Ps and/or AD. Nine hundred and eighty-three patients were studied--428 with Ps, 224 with AD, 45 with both Ps and AD, and 286 controls. Of AD patients 16.7% had Ps, and 9.5% of Ps patients had AD. In consecutive occurrences, Ps generally followed AD. The ratio of concurrent to consecutive incidences was 3:1. The two diseases are shown not to be mutually exclusive and may coexist in the same individual.