Psoriasis: odd varieties in the adult.

Occasionally we observe particular varieties of psoriasis and in rare cases transitional features with other diseases, which pose problems concerning the differential diagnosis and the nosological classification. This communication deals with the following clinical and histological aspects of psoriasis: 1) Sebopsoriasis. Relationship of psoriasis to pityriasis rubra pilaris. 2) Erythema annulare centrifugum type of psoriasis. 3) Is subcorneal pustular dermatosis an expression of pustular psoriasis? 4) Salient histopathological criteria for the diagnosis of the different atypical forms of psoriasis. 5) Presentation of an unusal case with striated and retiform verrucous psoriasis-like eruptions, which show a relationship to parakeratosis variegata.