Recurrent, isolated factor X deficiency in myeloma: repeated normalization of factor X levels after cytostatic chemotherapy followed by late treatment failure associated with the development of systemic amyloidosis.

We describe the case of a 64-year-old woman with isolated severe factor X deficiency associated with kappa light chain myeloma. At the time of diagnosis there was no evidence for amyloidosis. Complete remission (CR) of myeloma as well as normalization of factor X levels were achieved after cytostatic chemotherapy. Subsequently, factor X deficiency recurred twice without any evidence for relapse of myeloma. The first time factor X normalized again following cytostatic treatment, the second time, however, factor X deficiency was refractory to chemotherapy. Finally, relapse of myeloma became evident associated with rapidly progressing, systemic amyloidosis, which was fatal within a few months. Initially, factor X infusion studies showed a normal recovery, but when amyloidosis became overt the recovery decreased to 0%. We assume that factor X deficiency was due to a binding of factor X to kappa light chains associated with the proliferation of the malignant myeloma cell clone.