Both traumatic hemolysis and microangiopathic hemolytic anemia produce red blood cell fragments, burr cells, and schistocytes (helmet cells) on peripheral blood smear.
Mechanical damage, such as that induced by a prosthetic valve, can cause excessive shear and turbulence in the cardiac circulation that damages red blood cells. The patient’s normal platelet count suggests that she is not suffering from microangiopathic anemia. Expected laboratory results also include a decreased hemoglobin level and an elevated reticulocyte percentage.
Dhaliwal et al. discuss the presentation and diagnosis of hemolytic anemia. They conclude that clinical presentation may include acute or chronic anemia, reticulocytosis, and jaundice. Characteristic laboratory findings include increased unconjugated bilirubin, increased lactate dehydrogenase, and decreased haptoglobin.
Bettadapur et al. review the clinical complication of prosthetic heart valves. They find that although severe hemolytic anemia is relatively uncommon, it may occur when RBCs are sheared and destroyed by turbulent blood flow across a foreign material such as a prosthetic cardiac valve.
Illustration A demonstrates schistocytes, fragmented and irregularly shaped RBCs.
Illustration B depicts burr cells (echinocytes), RBCs with short and evenly spaced projections frequently associated with uremia. Mechanical damage (traumatic hemolysis) and microangiopathic hemolysis can produce both cell types.
Answer 1: Bite cells and Heinz bodies are characteristic of glucose-6-phosphate dehydrogenase (G6PD) deficiency.
Answer 2: Sickle cells and target cells are characteristic of sickle cell anemia.
Answer 4: Round macrocytes and target cells are characteristic of marcocytic anemia from chronic alcoholism.
Answer 5: Macrocytes and hypersegmented neutrophils are characteristic of megaloblastic anemia.
Bettadapur MS, Griffin BP, Asher CR. Caring for patients with prosthetic heart valves. Cleve Clin J Med. 2002 Jan;69(1):75-87. Review
PMID:11811724 (Link to Abstract)
Dhaliwal G, Cornett PA, Tierney LM Jr. Hemolytic anemia. Am Fam Physician. 2004 Jun 1;69(11):2599-606.
PMID:15202694 (Link to Abstract)
USMLE World Step 1 QBank Question #1297. Copyright © USMLEWorld, LLC 2012.