Subunits A and S inheritance in four families with congenital factor XIII deficiency.

Previous studies of the inheritance of the two molecular subunits of fibrin stablizing factor (factor XIII) refer to isolated cases. The present work investigates the hereditary mode of transmission of subunits A and S, measured by the Laurell technique, in seven homozygotes and in 29 heterozygotes belonging to four families with factor XIII deficiency. The results indicate that the homozygotes were devoid of immunologically identifiable A subunit, whereas the heterozygotes could be identified by measuring this protein. The subunit S has been found to be decreased both in homozygous and in heterozygous patients, so that it seems that the two subunits, even if their synthesis is controlled by different genes, are genetically related. The mode of transmission of this disorder, supported by quantitative determinations of plasma subunit A, is autosomal recessive.