Analysis of linkage between the major histocompatibility system and juvenile, insulin-dependent diabetes in multiplex families. Reanalysis of data.

Linkage analysis between the major histocompatibility system (HLA) and juvenile, insulin-dependent diabetes, assuming an autosomal recessive mode and 50% penetrance was performed on 21 juvenile, insulin-dependent diabetic multiplex families (two or more diabetics per sibship) with phenotypically normal parents. The total lod score was the highest (3.98) at a recombination fraction of 13%. For a penetrance of 100%, the highest total lod score was 2.92 at a recombination fraction of 18%. These results are compatible with the existence of linkage between an autosomal recessive diabetic gene with 50% penetrance and the HLA in some of the families studied. Our ascertainment strategy would be expected to increase the likelihood of selecting for genetically homogenous diabetes and against sporadic forms of the disease. Thus, our findings may apply only to a small proportion of all cases of juvenile, insulin-dependent diabetes.