The course of psoriasis is inconsistent. It follows an irregular chronic course marked by remissions and exacerbations of unpredictable onset and duration. Two of the chief features of psoriasis are its tendency to recur and persist.
Psoriasis occurs with equal frequency in both sexes.
The onset of psoriasis is at a mean age of 27 years, but the range is wide, from a few months to the seventies. There appears to be a genetic predisposition and Caucasians seem to be more affected than other races. It is uncommon in those of Afro-Caribbean origin. American Indians and native Fijians do not have psoriasis. In Western medicine, the cause of psoriasis is still not clear, although it is believed to be a hereditary skin condition, triggered by infections or psychogenic factors.