Acute hemolytic anemia

Classification is based on:


Laboratory findings typically include a normochromic, normocytic anemia with reticulocytosis or rarely reticulocytopenia. Occasionally, a high mean corpuscular volume may result from reticulocytosis or antibody-induced agglutination of erythrocytes. White blood cell count and platelet count are normal or slightly elevated. An indirect hyperbilirubinemia is usually present, but hepatic and renal functions are normal unless the patient has suffered cardiovascular collapse. Haptoglobin level < 25 is 96% specific for hemolysis, but it is an acute phase reactant and a very sensitive test.

Acute lymphoblastic leukemia typically presents with abnormalities of two or more hematologic cell lines, not with an isolated anemia, as described in the vignette. Also, the reticulocytosis demonstrates a normal and robust response to anemia, which would not be seen in acute leukemia, where normal hematopoiesis is replaced by an infiltration of leukemic blasts.

Although acute myocarditis may present with exercise intolerance and physical findings of congestive heart failure, severe anemia and hyperbilirubinemia would not be seen.

Patients who have underlying hemolytic anemias, such as sickle cell disease or hereditary spherocytosis, may develop severe anemia in the setting of infection with parvovirus B19. In these patients, this infection is characterized by an aplastic crisis, which may manifest as a change in exercise tolerance severe enough to warrant transfusion. However, the reticulocytosis described in  the vignette is not consistent with an aplastic crisis related to parvovirus B19 infection.

Children who have hemolytic-uremic syndrome may present with pallor, lethargy, and exercise intolerance. However, physical examination findings typically include hypertension, petechiae, and often edema. Laboratory evaluation reveals not only a hemolytic anemia, but also renal insufficiency and thrombocytopenia.

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