Haemophilia A: carrier detection by DNA analysis.

From 46 families of predominantly German origin, afflicted with haemophilia A, 178 females were tested for carrier status. Two polymorphic restriction endonuclease sites, the extragenic marker locus DXS 52 (St 14 probe) and the intragenic Bcl I RFLP were investigated in these families. In some cases the results were corroborated by identifying (i) deletions within the factor VIII:C gene and (ii) eliminating a restriction endonuclease site. Two new alleles of the DXS 52 marker locus were found. According to this strategy, 27 women were classified as carriers and 74 as non-carriers. Forty-six women were classified as carriers according to pedigree analysis. Twenty-five females of families with sporadic cases and 6 test persons, who had mothers who where homozygous for the marker alleles, were diagnosed by additional use of conventional carrier detection.