A 32-year-old woman with systemic lupus erythematosus (SLE) and chronic renal failure manifests rapidly progressive weakness. On physical examination, she appears pale and has slightly yellow sclerae and an enlarged spleen. Blood tests reveal severe anemia and mild, mostly unconjugated, hyperbilirubinemia. Coombs test is positive at 37 C but negative at 0-4 C. This patient developed anemia because of?

First, what type of anemia is it? It must be a hemolytic form, since it is associated with unconjugated hyperbilirubinemia (hence the yellow sclerae), resulting from increased destruction of red blood cells. Increased erythrocyte destruction is the cause (not the effect) of splenomegaly. Fuhermore, a positive Coombs test implies that hemolysis is mediated by antibodies attached to red blood cells. Thus, the correct choice must be either IgG or IgM. Since the Coombs test is positive at warm temperature (37 C), the antibody is a warm agglutinin. Warm agglutinins are viually always of IgG type and may be triggered by a variety of disorders, including lymphomas, drugs, and autoimmune diseases such as SLE. IgG-coated red cells are then sequestered by the spleen, where hemolysis occurs, thus explaining splenomegaly. By contrast, cold agglutinins are IgM and can be demonstrated by Coombs test at cold temperature (0-4 C). Cold agglutinins are usually triggered by Mycoplasma pneumoniae infection or lymphomas. Note: Bone marrow aplasia is due to failure or suppression of myeloid stem cells, with decreased production of red blood cells, platelets, and leukocytes (pancytopenia). Most commonly, this condition is caused by chemical agents (especially drugs such as chloramphenicol, phenylbutazone, alkylating agents, and antimetabolites) or total body irradiation. Renal failure causes normochromic, normocytic anemia because of decreased synthesis of erythropoietin. Erythropoietin administration is currently the standard treatment for this form of anemia. Although renal failure is a frequent consequence of SLE, there is no evidence that it plays a role in this patient's anemia. Ref: Reid M.E. (2010). Chapter 137. Erythrocyte Antigens and Antibodies. In J.T. Prchal, K. Kaushansky, M.A. Lichtman, T.J. Kipps, U. Seligsohn (Eds),Williams Hematology, 8e.