A septic patient in the ICU has falling hemoglobin, platelet count 40 x 10^9/L, prolonged PT and aPTT, and a peripheral smear showing helmet cells and fragmented red cells. The primary mechanism of the fragmented cells is:
- A Mechanical shearing of red cells by fibrin strands in small vessels ✓
- B Autoantibody-mediated removal of red cell membrane by splenic macrophages
- C Oxidant denaturation of hemoglobin forming Heinz bodies
- D Defective spectrin assembly causing membrane loss
Correct answer: A. Mechanical shearing of red cells by fibrin strands in small vessels
Explanation
Disseminated intravascular coagulation produces widespread fibrin deposition in the microcirculation, and red cells are sliced as they pass through these strands, generating schistocytes and helmet cells. This defines microangiopathic hemolytic anemia. Splenic macrophage trimming yields spherocytes, oxidant injury yields bite cells and Heinz bodies, and defective spectrin assembly is the membrane skeleton defect of hereditary elliptocytosis, none of which produce fragmentation.
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.