Is there a genetic basis for psoriasis?

Although a specific genetic abnormality has not been identified, psoriasis is generally considered to be a genetically determined disease. There are reports of striking family pedigrees that suggest an autosomal dominant inheritance, but with only partial penetrance. Keep in mind that psoriasis is probably not a single disease, but a family of diseases involving epidermal hyperproliferation. The external environment presumably plays a role in the clinical expression. The strongest evidence for the importance of external factors in the expression of psoriasis is seen in acute guttate psoriasis, which often occurs in association with streptococcal pharyngitis.

Travers JB, Hamid QA, Norris DA, et al: The environment of psoriasis allows enhanced reactivity to epicutaneously applied bacterial exotoxins, J Clin Invest 104:1181–1189, 1999.