A 33-year-old previously healthy man with persistent fever and heart murmur is diagnosed with infective endocarditis. He receives a high dosage of a cephalosporin antibiotic during the next 10 days. He now has increasing fatigue. On physical examination, he has tachycardia and scleral icterus. Laboratory studies show a hemoglobin level of 7.5 g/dL, platelet count of 261,000/ mm3, and total WBC count of 8300/ mm3. The direct Coombs test is positive. The peripheral blood smear shows reticulocytosis. Which of the following is the most likely cause of his anemia?
Correct Answer: Immune-mediated hemolysis
Description: Drug-induced hemolytic anemias are neither common nor severe enough to be recognized since the hemolysis is mainly extravascular. However, many patients receive drugs, so the potential for a drug reaction exists, and this immune-mediated mechanism must be distinguished from other causes for anemia. Cephalosporins are the most frequent drugs implicated. Treatment consists of cessation of therapy with the drug because most cases are due to drug-dependent antibody formation. Nutrient deficiencies reduce marrow production, so reticulocytosis is unlikely. DIC is unlikely with a normal platelet count. Parvovirus infection may suppress erythropoiesis transiently in individuals with normal red cells but may precipitate an aplastic crisis in those with a hemoglobinopathy. Persons with abnormal red cells are likely to have a history of anemia. Hemoglobinopathies are not Coombs positive.
Category:
Pathology
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