Genetic aspects of psoriasis.

Epidemiological studies indicate that genes play an important role in the pathogenesis of psoriasis. Multiple genes are likely to be involved, interacting not only with each other but also with the environment to cause disease expression. Molecular genetic studies indicate that there are multiple susceptibility loci present throughout the human genome. It is clear that a gene or genes of major impact on psoriasis is present on chromosome 6 within the major histocompatibility complex (MHC). Linkage disequilibrium studies indicate this gene to reside within a 300 kb interval centred around the centromeric end of class I MHC. Known candidate genes in this region are HLA-C, corneodesmosin and HCR, although novel genes, as yet unknown, may also exist. There is accumulating evidence that HLA-C is not itself the causative gene but rather a marker for it. Identification of the genes involved in psoriasis susceptibility will represent a step forward in our understanding of the disease and our future ability to help patients with psoriasis.