Streptococcal infection distinguishes different types of psoriasis: Table 1

### Key points Epidemiologically, the first manifestations of psoriasis are promoted by upper respiratory tract infections with Streptococcus pyogenes . Parallels to post-streptococcal disorders are obvious but still lack pathogenetic proof. Two types of non-pustular psoriasis, types I and II, can be distinguished according to age of onset, family history, and inheritance of certain HLA alleles. Here we show that only type I but not type II psoriasis is associated with streptococcal infection. Psoriasis vulgaris is a chronic inflammatory disease that affects 1.5-2% of people in western societies with severe and disabling inflammation of the skin and, occasionally, arthritis. It is currently regarded as an autoimmune-like disorder that is mediated by antigen specific activation of T cells in the skin of genetically predisposed subjects.1 A high incidence of streptococcal throat infections as the main trigger of first psoriasis exacerbation2,3 favours streptococcal antigens as causative agents that may induce cross reactive …