A 60-year-old African-American female is evaluated for fatigue. Past surgical history includes mitral valve repair with a mechanical valve due to severe mitral insufficiency. She has 30-pack year history of smoking and occasionally drinks alcohol. Examination shows pallor. Laboratory studies show the following:Complete blood count Serum chemistries are within normal limits. Her peripheral smear shows red blood cell fragments, "burr cells," and "helmet cells". Which of the following is the most likely cause of her condition?

Question

A 60-year-old African-American female is evaluated for fatigue.  Past surgical history includes mitral valve repair with a mechanical valve due to severe mitral insufficiency.  She has 30-pack year history of smoking and occasionally drinks alcohol.  Examination shows pallor.  Laboratory studies show the following:Complete blood count  Serum chemistries are within normal limits.  Her peripheral smear shows red blood cell fragments, "burr cells," and "helmet cells".  Which of the following is the most likely cause of her condition?

Quizplus · Accepted Answer

All of the choices represent mechanisms for anemia. The key to answering this question is this patient's history and peripheral smear. Red blood cell fragments, burr cells and helmet cells are consistent with traumatic hemolysis, which can result from either microangiopathic hemolytic anemia or mechanical damage (e.g. prosthetic valve). Prosthetic valves produce excessive shear and turbulence in the cardiac circulation, causing mechanical trauma to the RBCs. Burr cells are erythrocytes with short, evenly-spaced projections. They can occur as an artifact or in association with uremia, pyruvate kinase deficiency, microangiopathic hemolytic anemia, or mechanical damage. (Choice A) Microvascular thrombi are the pathophysiologic mechanism for microangiopathic hemolytic anemia, which causes thrombocytopenia. In this patient, platelet count is normal. (Choice B) Cytoskeleton abnormalities describe an intracorpuscular defect characteristic of a group of anemias that includes hereditary spherocytosis, hereditary elliptocytosis, and hereditary stomatocytosis. Respectively, spherocytes, elliptocytes, or stomatocytes are characteristically seen in the peripheral blood smear. (Choice C) Impaired DNA synthesis is the pathophysiologic mechanism for megaloblastic anemia. Ovalo-macrocytes are the associated morphologic RBC variant seen in this group of anemia. In addition, hypersegmented neutrophils are also characteristic. (Choice D) Gastrointestinal blood loss results in hypochromic, microcytic anemia due to iron deficiency. (Choice E) Mutation of the beta globin chain results in beta thalassemia; target cells are the RBC morphologic variant commonly seen. (Choice F) Paroxysmal nocturnal hemoglobinuria is an episodic hemolysis caused by a complement-mediated mechanism. Leukopenia and thrombocytopenia (pancytopenia) are commonly associated. Educational Objective:

A 60-Year-Old African-American Female Is Evaluated for Fatigue