A 3-year-old boy is brought to the physician with jaundice and pallor. He was adopted and his family history is unknown. Laboratory studies show anemia, reticulocytosis, and increased indirect bilirubin. A peripheral blood smear shows red blood cells without central pallor. This patient is most likely to have which of the following additional findings?
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This patient's anemia, reticulocytosis, and increased indirect bilirubin are indicative of hemolytic anemia. His peripheral blood smear shows red blood cells without central pallor (ie, spherocytes), which suggests acquired or hereditary spherocytosis. Hereditary spherocytosis is caused by defective binding of the red cell cytoskeleton to the plasma membrane due to mutations involving ankyrin, band 3, or spectrin proteins; acquired spherocytosis is most often caused by autoimmune hemolytic anemia. Compared to normal red blood cells, spherocytes are smaller and have a more intensely-staining cytoplasm due to membrane loss and red cell dehydration. The red cell index most specific for spherocytosis is an elevation in mean corpuscular hemoglobin concentration (MCHC).
(Choice A) Lactate dehydrogenase (LDH) is an enzyme present in red blood cells. LDH will be elevated in any cause of hemolytic anemia.
(Choice B) Haptoglobin is an acute phase reactant that combines with free hemoglobin in the circulation to preserve body iron stores and prevent tissue damage. Haptoglobin levels decrease in any form of hemolytic anemia (even with extravascular hemolysis, as some free hemoglobin will spill into the blood stream).
(Choice D) The mean corpuscular volume (MCV) is generally normal to low in hereditary spherocytosis.
(Choice E) Red blood cell inclusions, such as Howell-Jolly bodies (DNA) and Pappenheimer bodies (iron), are occasionally associated with hemolytic anemia but are more commonly associated with splenectomy and sideroblastic anemia, respectively.
Educational objective:
In spherocytosis, mean corpuscular hemoglobin concentration (MCHC) is increased due to mild dehydration of the red blood cell. Markers of hemolysis are often evident and include elevated lactate dehydrogenase, reticulocytosis, and decreased haptoglobin.