<p>This invention relates to polymorphisms in the human epidermal gene cluster in the major histocompatability complex. In particular, the invention relates to four polymorphisms in the sequence of the alpha-helix coiled-coil rod homologue (HCR) gene, the structure of the corresponding allelic polypeptides encoded thereby, and the similarity of these polypeptides with streptococcal surface antigen M proteins. The invention provides diagnostic assays for, and methods of manufacture of medicaments for both prophylaxis and treatment of guttate psoriasis and/or psoriasis vulgaris.</p>
