Early complement component depletion and mixed cryoglobulinemia in a “healthy” family

A family containing two apparently healthy brothers with profound early complement component depletion (C1, C4, C2) and mixed IgG‐IgM polyclonal cryoglobulins was studied. The cryoglobulins possessed rheumatoid factor activity and depleted early complement components in normal human serum. Circulating immune complexes could not be detected by utilizing standard methods. The phenomenon was not HLA‐linked. This study demonstrates the familial occurrence of a chronic hypocomplementemic state associated with cryoglobulinemia in clinically normal subjects.