IDDM9 and a locus for rheumatoid arthritis on chromosome 3q appear to be distinct

Markers near a locus for type 1 diabetes on chromosome 3q22-q25 (IDDM9) demonstrate linkage to rheumatoid arthritis, however it is not clear whether these two loci overlap. Sex-specific linkage analysis may be of interest for rheumatoid arthritis on chromosome 3q since linkage of type 1 diabetes to IDDM9 derives predominantly from affected female sibpairs, and rheumatoid arthritis is more common in females than males. Using data from a recent genome scan for rheumatoid arthritis and sex-specific linkage analysis we show that linkage of rheumatoid arthritis to chromosome 3q peaks approximately 30 cM centromeric to IDDM9. Furthermore, there is no evidence for linkage to IDDM9 in females with rheumatoid arthritis.