HLA haplotypes in families with high frequency of multiple sclerosis.

Eight families from southern Sweden having two or more members with multiple sclerosis (MS) were typed for various alleles of the HLA system. The MS patients within each family shared one major histocompatibility system (MHS) haplotype, which was identical to the hitherto-described MS-associated haplotype A3B7Dw2 only in two of the families. Healthy relatives of MS patients were often found to carry the same haplotype as the affected members, which makes an estimate of the degree of penetrance of disease in individuals carrying the MS-predisposing MHS-linked gene possible.