A case of rheumatoid hyperviscosity syndrome with characterization of the serum immune complexes

The clinical and immunologic data in a case of rheumatoid arthritis complicated by serum hyperviscosity are reported. The elevation in the serum viscosity was accompanied by the presence of intermediate immune complexes which were partially purified from the patient's serum by gel filtration chromatography. These complexes had a molecular weight of approximately 510,000 daltons and contained polyclonal IgG and IgA immunoglobulins. The hyperviscosity syndrome in this patient was likely due to the presence of intermediate complexes and unrelated to the rheumatoid factor activity which was found predominantly within the IgM fraction of the serum. This case demonstrates that the hyperviscosity syndrome may, in rare cases, develop as a complication of rheumatoid arthritis. It is important to consider this possibility before the clinical symptoms of increased serum viscosity become manifest.