Mode of Inheritance in Psoriasis

To the Editor.— In the JuneArchives(1980;116:718-719), Cutler et al argued that "the bulk of current evidence supports the hypothesis that the mode of inheritance in psoriasis is autosomal dominant." In an editorial in the same issue (1980;116:657), Dobson discusses the difficulty of resolving the controversy surrounding the mode of inheritance and remarks "it may well be that psoriasis is not a single disorder but the phenotypic expression of various heritable and nonheritable processes." An analysis of the frequency distribution in relation to the age at onset of psoriasis in 1,356 patients treated in Leeds, England, gave clear evidence of bimodality in women and possible trimodality in men. 1 From the detailed form of the distributions, we concluded that two genotypes predispose to psoriasis in women and at least two (possibly three) in men. For onset from infancy to 25 years of age, the ratio of female to male