Genetic analysis of families with multiple cases of rheumatoid arthritis.

We examined the inheritance of susceptibility to RA in families with multiple cases of RA, and studied existence of any linkage between the putative RA disease susceptibility locus and the HLA-DR locus. A pedigree analysis programme, PAP, was used for both analyses. Our investigation suggests that familial RA is the effect, in part, of an inherited autosomal dominant susceptibility gene with incomplete penetrance rather than that of a recessive gene. Linkage analysis indicates a tight linkage between the putative RA disease susceptibility locus and the HLA-DR locus under an autosomal dominant mode of inheritance.