Many work stress that people with psoriasis have a well-defined HLA system. In 66% of them found HLA CW6. Clearly, there is a specific constellation called CW6, which is located on the C gene at chromosome 6. It is not a genetic abnormality, but a factor associated with psoriasis. Kind of like red argues that the present distinction of having the skin more sensitive to UV rays than brown. This gene has therefore been no change. Moreover, the mere fact of being a carrier of this gene does not necessarily psoriasis since 10% of the general population is HLA CW6. Conversely, there are patients who do not carry this gene. Given all these data, measuring how psoriasis is a complex disease. We understand why scientists are wondering whether the various types of psoriasis (plaque psoriasis, pustular psoriasis, psoriatic arthritis) do not correspond to distinct diseases, and involving different susceptibility genes vary clinical forms. The fact that the age of onset of the disease, and variability of its development (some patients will only push while others will have to live with the disease during their lifetime) researchers confirm this hypothesis. The wealth of scientific studies conducted around the world testifies to the involvement of other genes responsible for this skin disease.