Factor XIII deficiency. A family study by measurement of factor XIII subunits A and S.

A girl with congenital factor XIII deficiency and her large family have been studied by electroimmunoassay of factor XIII subunits A and S. The homozygote has absence of subunit A and a decreased level of subunit S. The heterozygotes have decreased levels of both subunits, and were more readily identified by measurement of subunit A than by the ratio subunit S/subunit A. The mother of the propositus appears to be a new heterozygote, but heterozygosity on the paternal side is traced through three generations.