Incomplete fibrin formation and highly elevated Factor XIII activity in multiple myeloma.

Bleeding is a common complication in patients suffering from multiple myeloma. In some cases a defect in fibrin formation has been suggested as one possible cause of haemorrhagic tendency. As shown in this investigation the defect in fibrin formation, ascertained using PAGE, is due to a lack of alpha-chain polymerization of fibrin monomers in 5/11 patients with IgG myeloma and in 2/5 patients with IgM paraproteinaemia. No disturbed fibrin polymerization could be observed in IgA myeloma (n = 6). Factor XIII concentrations of subunit A and to a lesser extent of subunit S (Laurell technique) were highly elevated in all cases with regular fibrin formation. comparable values were obtained by measuring the transamidase activity of factor XIII by incorporation of 14C-labelled purtrescin into casein. Levels up to 600% of normal could be recorded. In contrast, all patients with a lack of alpha-chain polymerization had a factor XIII activity within the normal range. Addition of factor XIII concentrate to plasma from patients with defective fibrin formation led in 5/8 cases to a partial cross-linking of alpha-monomers. we conclude that in some cases paraproteins can inhibit the factor XIII and prevent its action on fibrin.