A 50-year-old man with sepsis has a falling hemoglobin and platelet count. Peripheral smear shows helmet cells and fragmented red cells without polychromasia of uniform size. The direct antiglobulin test is negative. The mechanism of his anemia is:

• A Mechanical fragmentation of red cells crossing fibrin strands in microvasculature ✓
• B Complement mediated intravascular lysis
• C Macrophage mediated extravascular destruction in the spleen
• D Oxidant denaturation of hemoglobin with Heinz body formation

Explanation

Microangiopathic hemolytic anemia occurs when red cells are sheared by fibrin strands deposited in small vessels during DIC, TTP, HUS, or malignant hypertension, producing schistocytes and helmet cells. The negative Coombs test excludes immune hemolysis, and complement mediated lysis would suggest PNH rather than fragmentation. Extravascular destruction produces spherocytes, and Heinz bodies indicate oxidant injury such as G6PD deficiency, neither of which matches the fragmented morphology described.

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.