Porokeratosis of Mibelli induced by topical corticosteroid.

BACKGROUND: [corrected] Prorokeratosis of Mibelli is a chronic disorder characterised by slightly atrophic plaques surrounded by keratotic border.

METHODS AND RESULTS: A 45-year-old with clobetazole propionate ointment for psoriasis over 15 years developed characteristic lesions of porokeratosis Mibelli on the elbows. Histopathological examination revealed the cornoid lamellae located on the edges of the specimen and psoriasiform acanthosis and a spongiotic pustule formation in the center of the specimen; thus, it was suggested as 'psoriasis encircled by porokeratosis'.

CONCLUSIONS: Development of porokeratosis may be explained by the local immunosuppressive effect of the prolonged application of the topical steroid.