A 55-year-old woman has slowly worsening anemia, mild jaundice, and splenomegaly. Direct antiglobulin (Coombs) test is strongly positive at 37 degrees Celsius. Peripheral smear shows numerous spherocytes without evidence of schistocytes or fragmented cells. The predominant antibody class and site of red cell destruction are:

• A IgM, intravascular lysis by complement in the circulation
• B IgG, extravascular phagocytosis by splenic macrophages ✓
• C IgG, complement-mediated intravascular hemolysis in renal vasculature
• D IgA, hepatic Kupffer cell sequestration

Explanation

Warm autoimmune hemolytic anemia is caused by IgG antibodies reactive at body temperature. IgG-coated cells lose membrane to splenic macrophage partial phagocytosis, forming spherocytes that are destroyed extravascularly in the red pulp. Cold agglutinin disease uses IgM and complement-mediated intravascular lysis, making option A describe the wrong entity. First-line treatment is corticosteroids, and secondary causes include lymphoproliferative disease, lupus, and drugs such as methyldopa.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.