Variant of Factor IX Deficiency in Female with 45, X Turner’s Syndrome

The case of an 11-year-old girl with a severe bleeding diathesis, a factor IX level of 4 per cent, and 45, X Turner’s syndrome is described. Family studies revealed severe factor IX deficiency in 4 male relatives and mild deficiencies in 4 heterozygous female carriers. The B_m or B⁺ variant of this disorder was demonstrated in all affected members of the kindred.