Summary

exclude the possibility of a new, dominant mutation. The possibility that it may be a characteristic of exogenous origin must also be kept in mind. Against the assumption that it is a heterozygous manifestation of the gene which in homozygous form manifests itself in the syndrome, is the circumstance that none of the homozygotes, i.e. the probands, have polydactyly. The marked similarity among the probands with regard to the clinical picture of the syndrome speaks against the assumption that the isolated polydactyly is a homozygous manifestation of the gene in question. Against this assumption, also, is the circumstance that the ancestors of the father can be traced back to an entirely different part of Sweden from that of the probable heterozygous lines in the ancestors of the probands. No conclusive evidence for any of the interpretations presented here has been obtained. In our opinion it is not probable that the polydactyly in this case is genetically associated with the syndrome. The question must, however, remain open. Two of the three proband parents, examined audiometrically, have a neurogenous hearing impairment. It does not seem unlikely to us that this represents a heterozygous manifestation of the pathological recessive gene, but no definite conclusions in this respect can be drawn on the basis of the small number of observations made. Even the decreased glucose tolerance observed in two of the parents can be interpreted in this way. Our aim is to extend the investigation by examining the cases of L.M.B.B. already registered by us, and such others as may be traced in Sweden. These cases will be examined by the same methods as those used for the present cases, including the determination of the sex chromatin pattern. In addition a careful genealogical study of their families will be made. Through a combined clinical and genetic analysis of these families it ought to be possible to shed further light on the problems dealt with in the present work.