Abstract

Background: Multiple sclerosis (MS) is a disease widely believed to be autoimmune in nature. Genetic-epidemiological studies implicate susceptibility genes in pathogenesis, although non-MHC susceptibility linkages have been difficult to confirm. Insight into pathways intrinsic to other complex diseases has come from the genetic analysis of large, autosomal dominant kindreds. Here we present a genetic study of a large and unique kindred in which MS appears to follow an autosomal dominant pattern of inheritance with consistent penetrance in 4 generations.

Methods: Eighty-two individuals of this 370 member family were genotyped with 681 microsatellite markers spanning the genome with an average spacing of 5.3 cM.

Results: Parametric linkage analysis was performed and no significant LOD score (LOD>3.3) was observed. For a rare dominant disease model with reduced penetrance, 99.6% of the genome was excluded at a lod score <-1 and 96% at a lod score <-2. The HLA-DRB1 candidate gene was also genotyped by allele-specific methods. In each instance where at least one parent was positive for HLA-DRB1*15, one or more HLA-DRB1*15 alleles were transmitted to the affected offspring (11/11). HLA-DRB1*15 was transmitted equally from both the familial and the married-in parents and therefore this locus does not appear to be the autosomal dominant acting gene in this family but an important modifier of risk.

Conclusions: These results further stress the importance of the HLA-DRB1*15 bearing haplotype in determining MS susceptibility. Furthermore this study highlights the complexity of MS genetics; even in the presence of a single family seemingly segregating MS as an autosomal dominant trait.