[Genetic study of mani-depressive psychoses].

The aim of the present work is to investigate the heredity of manic-depressive syndromes, in particular to test the hypothesis of a dominant X-linked transmission in these disorders. The Maximum Likelihood Estimate method was applied to linkage analysis between several X-linked genetic markers and bipolar manic-depressive illness, as well as to a control population of unipolar depressive patients. The genetic markers studied were deuteranopia and protanopia (two X-linked recessive markers) and the Xg blood group (X-linked dominant marker). The sampling methods were identical for both groups of patients and the family studies were performed "blind" (i,e. without knowledge of the proband's diagnosis). The results demonstrate the presence of strong linkage between manic-depressive (bipolar) illness, deuteranopia and protanopia. Linkage (although less strong) was also shown for bipolar illness and the Xg blood group. The genetic data are based on mathematical analysis of 36 informative kindreds ascertained from a sample of 134 manic-depressive patients. The results are concordant and demonstrate that, in this sample, manic-depressive (biopolar) psychosis is genetically transmitted through a X-linked dominant factor. We have also demonstrated the absence of linkage between unipolar depressive illness and the studied genetic markers in 16 informative kndreds ascertained from a sample of 71 unipolar patients. The genetic analyses described in this study demonstrate the existence of a manic-depressive syndrome which phenotype is dominant and determined by a gene located on the short arm of the Xchromosome. Apart from some forms of mental deficiency, manic-depressive psychosis represents the first known instance of a mendelian heredity machanism in psychiatric disorder;