Psoriasis has been the subject of intense investigation in many parts of the world, but the cause of this skin disease still remains an enigma. Among studies on psoriasis, a comprehensive data gathering endeavor has provided a valuable resource for the study of the genetics of psoriasis.
In the search for the etiology of any disease, a good beginning is to establish whether there is an hereditary involvement. A genetic component has long been suspected for psoriasis. Our studies on genetic and environmental factors support the hypothesis that psoriasis is compatible with multifactorial inheritance. Multifactorial inheritance is a condition in which the heritable components are alleles at an unspecified number of loci, each contributing a small effect, along with environmental factors to the phenotype.
We are aware of the methodological pitfalls of the investigative approaches.1 For example, the application of the twin method in the genetics of psoriasis illustrates