LIFE-THREATENING, ANTIGLOBULIN TEST-NEGATIVE, ACUTE AUTOIMMUNE HEMOLYTIC-ANEMIA DUE TO A NON-COMPLEMENT-ACTIVATING IGG1-KAPPA COLD ANTIBODY WITH PRA SPECIFICITY

A 21-year-old man with fulminant cold autoantibody hemolytic anemia (CAHA) was hospitalized with hemoglobinemia, hemoglobinuria, hemoglobin concentration of 3.3 gm per dL, a negative direct antiglobulin test (DAT) with polyspecific and anti-C3d reagents, a negative Donath-Landsteiner test, and a cold agglutinin titer of 80. He failed to respond to corticosteroids, multiple plasma exchanges, and cyclophosphamide; he required 54 transfusions in 10 days to maintain a hemoglobin concentration of 6.0 to 10.0 g per dL. He improved dramatically after a splenectomy was performed. The wide-thermal-amplitude cold agglutinin proved to be an IgG1 κ antibody with Pr(a) specificity. The patient's serum exhibited normal complement activation. When the DAT was carried out at 0 to 4°C, the result was strongly positive for IgG; the indirect antiglobulin test at 0 to 4°C was positive with the patient's serum diluted 1 in 640. Within 6 months, he was in complete remission and receiving no therapy. As compared with eight patients with CAHA that was exclusively IgG-mediated, this patient is remarkable for his requirement for many transfusions and for DATs that were consistently negative for C3d.