HLA antigen frequencies in familial Crohn's disease (CD).

A possible association of Crohn's disease (CD) with MHC (major histocompatibility complex) markers was investigated in families with more than one affected member. HLA-A, B, C, DR and DQ typing was performed in 21 CD families with two or more CD patients. The following HLA-antigens showed increased relative risk (RR) values for CD: B44 (RR = 2.43; B15 (Bw62, Bw63) (RR = 2.03); DR7 (RR = 1.85); DR4 (RR = 1.06). Three of 44 patients were DR4- and four DR7-homozygous. The risk haplotype B44/DR7 was observed in four and Bw62/DR4 in three CD patients, respectively. CD affected family members (female greater than male) shared HLA haplotypes more frequently than expected by mendelian laws. None of the differences reached statistical significance.