[Factor X deficiency and systemic amylosis].

The case of a 52-year-old patient with systemic amylosis diagnosed upon examination of an osteomedullary biopsy specimen is reported. The most prominent clinical manifestation was a major hemorrhagic syndrome which was recognized as being a result of severe factor Stuart deficiency. The new classification of amyloses based on the latest biochemical and immunological findings is recalled. Current physiopathogenic speculations put emphasis on plasmocyte-macrophage cooperation. Lastly, factor Stuart deficiency, which is as classical as it is uncommon, could originate in the particular affinity of amyloid fibers for this factor and in a "mass effect" (quantity of amyloid substance directly exposed to blood flow), explaining why splenectomy is effective in some instances.