Cryoglobulinemia and cutaneous vasculitis in human brucellosis.

We report the occurrence of cryoglobulinemia and cutaneous vasculitis in three patients with brucellosis caused by Brucella melitensis. The isolated cryoglobulins were characterized as mixed polyclonal or type III. Brucella agglutinin activity was not detected in any of the cryoglobulins analyzed. However, the same agglutinin titer and the presence of precipitin lines of identity in immunodiffusion gels were observed in the supernatant of the cryoglobulins and the serum. Rheumatoid-factor activity was present in all the cryoprecipitates tested. Resolution of the purpuric lesions with therapy coincided with a decrease in serum cryoglobulins and, in one patient, with normalization of his serum C3 levels. These findings suggest that the immunological abnormalities manifested by our patients were the direct consequence of the brucellosis infection and provide additional evidence to support the role for immunological mechanisms in the pathogenesis of human brucellosis.