Autoimmune hemolytic anemia due to IgA class autoantibodies.

Autoimmune hemolytic anemia due to warm-reacting autoantibodies solely of the IgA class is very rare, and only five cases were identified among 5,177 patients referred during 13.5 years. All were females (ages 21-69 years) and all presented with idiopathic "Coombs negative" autoimmune hemolytic anemia, a diagnosis that was confirmed using monospecific anti-human IgA reagents. Red cell-bound IgG was reduced, but in two patients IgM was initially increased, an occurrence that was thought to reflect the developing autoimmune response. The autoantibodies had high affinity for red cells with very little free antibody detectable in the serum; in two instances Rh specificity was evident. Hemolysis was severe in four patients. Two of them had intravascular hemolysis, one of whom also had marked dyserythropoiesis and a transiently positive Ham's test. Although IgA autoantibodies caused hemolysis predominantly through immune adherence, on occasions they also seemed to be able to induce complement activation, possibly via the alternative pathway. Prednisolone was the mainstay of treatment, and was occasionally augmented with azathioprine and intravenous immunoglobulin. Blood transfusion was required in two patients, both of whom eventually required splenectomy that resulted in full remission. The one patient with mild hemolysis recovered without treatment.