MSAP for Students 5 by Unknown

Author:Unknown
Language: eng
Format: epub
Publisher: ACP
Published: 2011-02-21T16:00:00+00:00

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Item 9 — Answer: A

Educational Objective: Diagnose autoimmune hemolytic anemia.

This patient has autoimmune hemolytic anemia (AIHA). The hemolytic anemias are characterized by increased destruction of erythrocytes associated with reticulocytosis. Elevated levels of unconjugated bilirubin, lactate dehydrogenase, and uric acid and depressed levels of haptoglobin are characteristic of hemolysis. AIHA may be idiopathic or result from drugs, lymphoproliferative disorders, collagen vascular diseases, or malignancies. Warm antibody-mediated hemolytic anemia, the most common type of AIHA, is diagnosed by the direct antiglobulin (Coombs) test, which detects IgG or complement on the cell surface, and the presence of spherocytes on the peripheral blood smear. In this condition, IgG antibodies bind to Rh-type antigens on the erythrocyte surface at 37.0°C (98.6°F).

Hereditary spherocytosis is a congenital hemolytic anemia caused by abnormalities in erythrocyte membrane proteins and is characterized by spherocytic erythrocytes with increased osmotic fragility due to their large volume/surface area ratio. It would be very unusual for a congential hemolytic anemia to be first diagnosed at this patient's age. Additionally, hereditary spherocytosis is not associated with positive results on a Coombs test. Spherocytes are small round cells that lack the typical central pallor of normal erythrocytes.

Microangiopathic hemolytic anemia is a nonimmune hemolytic anemia. As with other hemolytic anemias, it is characterized by reticulocytosis, elevated levels of unconjugated bilirubin, lactate dehydrogenase, and depressed levels of haptoglobin. Microangiopathic hemolysis may be associated with thrombocytopenia. Another distinguishing characteristic of microangiopathic hemolytic anemia is the presence of schistocytes on the peripheral blood smear. This finding was lacking on this patient's peripheral blood smear.

α-Thalassemia is a congenital hemolytic anemia. Patients with a two-α-gene defect have target cells and an absence of spherocytes on the peripheral blood smear and do not have positive results on a direct antiglobulin test.

Key Point

Warm antibody-mediated hemolytic anemia, a common complication of lymphoid malignancies, is characterized by spherocytes on the peripheral blood smear.

Bibliography

Hauswirth AW, Skrabs C, Schutzinger C, Gaiger A, Lechner K, Jager U. Autoimmune hemolytic anemias, Evans' syndromes, and pure red cell aplasia in non-Hodgkin lymphomas. Leuk Lymphoma. 2007;48(6):1139-1149. [PMID: 17577777]

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