A 56-year-old man is evaluated for increased fatigability. His past medical history is significant for diabetes mellitus, osteoarthritis, and severe aortic stenosis that required aortic valve replacement. His peripheral blood smear is shown on the slide below. Which of the following laboratory findings is most likely to be seen in this patient?

Question

A 56-year-old man is evaluated for increased fatigability.  His past medical history is significant for diabetes mellitus, osteoarthritis, and severe aortic stenosis that required aortic valve replacement.  His peripheral blood smear is shown on the slide below.  Which of the following laboratory findings is most likely to be seen in this patient?

Quizplus · Accepted Answer

11ec160b_397a_7286_9249_ff2633593fc5_MD0001_00 The fragmented erythrocytes shown on the slide above are called schistocytes or helmet cells. They are formed by mechanical trauma to erythrocytes as they circulate through the vasculature. This patient's schistocytes are most likely due to erythrocyte damage caused by his aortic valve prosthesis. Artificial (mechanical) valves are more traumatic for RBCs than porcine prostheses and frequently cause hemolysis. Schistocytes can also be formed from narrowing of the microvascular spaces, as seen in disseminated intravascular coagulation, hemolytic-uremic syndrome, and thrombotic thrombocytopenic purpura. Hemolytic anemia due to intravascular erythrocyte destruction results in laboratory findings similar to those in other types of hemolytic anemias, including an increase in serum indirect bilirubin. Intravascular erythrocyte damage also results in free hemoglobin in serum (hemoglobinemia) and urine (hemoglobinuria) as well as increased serum lactate dehydrogenase (LDH). Haptoglobin is a serum protein that binds to free hemoglobin and promotes its uptake by the reticuloendothelial system. Haptoglobin levels decrease when significant quantities of hemoglobin are released into the circulation, as occurs with intravascular hemolysis. (Choice A) Increased serum iron occurs in hemochromatosis most classically, but increased serum iron can also be iatrogenic. Hemochromatosis does not cause anemia, but it is associated with cirrhosis and increased incidence of hepatocellular cancer. Hemolysis does not usually have a significant effect on serum iron because the iron released from lysed RBCs remains bound to hemoglobin. (Choice C) Increased mean corpuscular volume (MCV) occurs in megaloblastic anemia (eg, folate/vitamin B12 deficiency) due to the presence of enlarged ovoid erythrocytes. Increased MCV may also occur with other forms of anemia due to a reactive increase in reticulocytes (large, immature RBCs); however, anemia caused by mechanical erythrocyte trauma usually results in decreased MCV due to the presence of small RBC fragments (schistocytes). (Choice D) A decreased reticulocyte count in the presence of anemia is characteristic of aplastic anemia. In hemolytic anemias, the reticulocyte count is increased to compensate for the increased destruction of RBCs. (Choice E) A decreased serum albumin level is associated with cirrhosis (decreased production), nephrotic syndrome (urinary loss), and protein-wasting enteropathy (bowel loss). Educational objective: Schistocytes (helmet cells) are fragmented erythrocytes. They occur secondary to mechanical trauma from microangiopathic hemolytic anemias or prosthetic cardiac valves (macroangiopathic). Intravascular hemolytic anemias are characterized by decreased serum haptoglobin levels as well as increased LDH and bilirubin.

A 56-Year-Old Man Is Evaluated for Increased Fatigability