Genetic aspects of psoriasis

Epidemiological studies indicate that genes play an important role in the p athogenesis of psoriasis. Multiple genes are likely to be involved, interac ting not only with each other but also with the environment to cause diseas e expression. Molecular genetic studies indicate that there are multiple su sceptibility loci present throughout the human genome. It is clear that a g ene 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 c entromeric 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 causativ e 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.