In autoimmune hemolytic anemia (AIHA), cold agglutinin disease is associated with IgM antibodies that fix complement optimally at 4°C. The characteristic RBC morphology seen on peripheral blood smear in cold AIHA is:

• A Schistocytes and helmet cells
• B RBC agglutinates (clumping) with relative reticulocytosis ✓
• C Spherocytes with polychromasia
• D Target cells with sickle forms

Explanation

Cold agglutinin disease is characterized by IgM antibodies (usually anti-I) that cause complement-mediated hemolysis and RBC agglutination at peripheral body temperatures. The peripheral smear shows RBC agglutinates/clumps. The direct Coombs test is positive for complement (C3d) only, NOT for IgG. Treatment involves avoiding cold exposure and rituximab. Schistocytes indicate microangiopathic hemolysis (TMA). Spherocytes are seen in warm AIHA (IgG-mediated) and hereditary spherocytosis.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.