Because of the high rate of alloimmunization in sickle cell patients, transfusion of red cells matched as closely as possible with those of the recipient is recommended. Viscosity of plasma proteins is influenced by the concentration and heavy-chain class of the paraprotein. IgM, being the largest plasma protein and nearly 100 percent intravascular, is most likely to cause hyperviscosity. IgA and IgG3 are more likely to aggregate and thus are also more likely than the other subclasses of IgG to be associated with hyperviscosity. As in leukostasis, the choice between plasma exchange and chemotherapy is a clinical decision guided mainly by the clinical symptoms and their rate of progression.
Plasma exchange can lower viscosity in hours, whereas most chemotherapy requires days.
There is some evidence that acute-onset renal failure caused by myeloma proteins can be improved by lowering the plasma concentration of paraprotein, but more data are needed before this can be considered an established indication. Despite the role that antibody and immune complexes play in hematologic cytopenia, there are no well-controlled studies supporting the use of plasma exchange. The available case reports usually describe plasma exchange as backup after failure of more established primary therapies. A recent direct comparison of plasma infusion versus plasma exchange with fresh frozen plasma replacement showed a better response to plasma exchange, which is now the treatment of choice for all but the mildest forms of thrombotic thrombocytopenia. A controlled study of sham plasma exchange in patients with polymyositis and dermatomyositis also failed to confirm therapeutic benefit from plasma exchange.