Biologic false-positive serologic tests for syphilis and other serologic abnormalities in autoimmune hemolytic anemia and thrombocytopenic purpura.

Autoimmune hemolytic anemia (AIHA), the first autoimmune disease to be recognized, is a manifestation of defective immune regulation. Although often associated with a lymphoid neoplasm or an overt immunologic disorder, AIHA frequently appears without apparent cause. Many patients with the "idiopathic" disease have been found to have various immunologic abnormalities in addition to the antibodies reacting with red cells. Although familial AIHA is uncommon, other autoimmune diseases and serologic abnormalities have been encountered in relatives of numerous patients. Few detailed family studies have been performed, but the available data suggest that predisposition to AIHA and to the associated immunologic disorders often is genetically transmitted. Less information is available about autoimmune thrombocytopenic purpura, in part because of the historic difficulty in recognizing autoantibodies that react with platelets. However, there is good evidence for genetically determined predisposing factors in some cases. Using the BFP reaction as an indicator, we add to the evidence that AIHA and autoimmune thrombocytopenia, like SLE, tend to occur in persons with a long-standing occult immunologic defect that often has a genetic basis. In our studies, 11 patients with AIHA or ITP had BFP reactions. The serologic abnormality in 4 had been known to precede the blood disorder by 6 to 44 years. Five of the patients had an additional disease believed to have an immunologic pathogenesis. Serologic abnormalities apart from the BFP reaction and the red cell or platelet antibodies were demonstrated in 9. Autoimmune diseases or serologic changes are known to have affected relatives of 5 patients, including 4 who had 1 or more relatives with BFP reactions. Serologic tests for syphilis were negative in 2 sibs with autoimmune thrombocytopenic purpura whose father had a chronic BFP reaction and thyroiditis, but all 3 had low levels of IgA and IgM. Lymphoproliferative disorders appeared in 3 of the patients with BFP reactions, and 2 had relatives with lymphoid neoplasms. A lymphoma occurred in a woman with cold agglutinin disease 21 years after the discovery of the erythrocyte antibody. Our observations support the view that an abnormality of cells of the immune system, often genetically determined, may predispose to serologic changes, immune deficiency, autoimmune diseases and neoplasia.