Extreme hypercomplementemia in the setting of mixed cryoglobulinemia.

Elevated levels of complement components, C3 and C4, are often seen in inflammatory diseases. They are generally not thought to be responsible for organ injury but simply reflect stimulation of the immune system. Extremely high elevations of these components are rarely seen. Such values are usually reported in patients with hematopoietic malignancies. We report here a case of C3 elevation to 9.22 g/L (5 times the upper limit of normal) and C4 elevation to 2.48 g/L (6 times the upper limit of normal). To our knowledge, no prior elevations of this magnitude have been reported previously from our institution or in the published medical literature (+/- MEDLINE search, using keywords hypercomplementemia, C3, C4, and lymphoplasmacytic lymphoma). In this case, there appeared to be no adverse end-organ damage from the excessive complement components or their activation.