Diagnostic Considerations
Congenital conditions
McLeod red cell phenotype and CGD: The gene that controls Kx expression on RBCs is adjacent to the locus involved in CGD. Large deletions in this region may result in the appearance of both CGD and acanthocytic McLeod red cells. Although most patients with CGD do not have both ailments, those in whom both genes are affected have a mild hemolytic anemia. Large deletions around the XK locus may also cause McLeod syndrome to be accompanied with Duchenne muscular dystrophy, retinitis pigmentosa, and ornithine transcarbamylase deficiency. [21]
Acquired conditions
Echinocytes or Burr cells: Acanthocytes should be distinguished from echinocytes (from the Greek word echinos, which means urchin). These cells appear with multiple small projections that are uniformly distributed on the red cell surface. Echinocytes occur in many conditions, including malnutrition associated with mild hemolysis due to hypomagnesemia and hypophosphatemia, uremia, hemolytic anemia in long-distance runners, and pyruvate kinase deficiency. In vitro, elevated pH, blood storage, ATP depletion, calcium accumulation, and contact with glass can lead to formation of echinocytes.
Differential Diagnoses
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This image (magnified X 2000) shows the spiculated thorny RBCs (acanthocytes) as observed in an individual with abetalipoproteinemia. These are indistinguishable from the acanthocytes shown in the next image, which are observed in an individual with spur cell hemolytic anemia. Used with permission from Little, Brown and Company.
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This image (magnified X 2000) demonstrates acanthocytes in an individual with spur cell hemolytic anemia associated with alcoholic cirrhosis. Acanthocytes, unlike echinocytes or burr cells, have fewer spicules. Used with permission from Little, Brown and Company.
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This image (magnified X 2000) shows echinocytes, or burr cells, a universal feature of uremia. The spicules of acanthocytes vary in length and width and project nonuniformly from the cell surface, while burr cells have regularly spaced, smoothly rounded crenulations. The second morphologic feature of RBCs in an individual with uremia is the presence of ellipsoid cells. Used with permission from Little, Brown and Company.
