Laboratory Studies
CBC count reveals mild-to-moderate normocytic anemia with an elevated reticulocyte count. Peripheral blood smear findings reveal 0.2-90% acanthocytes.
Iron and folate may be deficient.
Direct antibody test results are negative.
Blood group may show McLeod or null Lutheran phenotype.
Total bilirubin and lactate dehydrogenase levels are elevated, reflecting the degree of hemolysis.
Liver function tests and total protein and albumin levels are abnormal in liver disease.
Serum creatine kinase is elevated in chorea-acanthocytosis and McLeod syndrome.
Plasma lipid profile may be abnormal. In abetalipoproteinemia, plasma cholesterol levels are very low, less than 50 mg/dL. Plasma phospholipid levels are very low. Plasma apolipoprotein B is absent. Chylomicrons, VLDLs, and LDLs are absent. Serum triglyceride levels are very low, less than 10 mg/dL. Plasma sphingomyelin levels are relatively increased at the expense of lecithin. [12]
Levels of fat-soluble vitamins E, A, D, or K are decreased in abetalipoproteinemia, hypobetalipoproteinemia, and malnutrition.
Prothrombin time (PT) is prolonged in vitamin K deficiency.
Fecal fat is elevated in abetalipoproteinemia, hypobetalipoproteinemia, and malnutrition.
MTP or APOB sequencing may identify mutations (not widely available).
Endocrine studies may reflect hypothyroidism or panhypopituitarism.
Other Tests
Nerve conduction velocity test findings reveal slow nerve conduction and decreased amplitude of sensory potentials.
Electromyography findings reflect denervation in abetalipoproteinemia.
Procedures
Intestinal and peripheral nerve biopsy is indicated when abetalipoproteinemia is suspected.
Histologic Findings
Intestinal biopsy findings reveal engorgement of mucosal cells with lipid droplets and normal villi but a lack of apolipoprotein B using immunofluorescence.
Peripheral nerve biopsy findings reveal paranodal demyelination in abetalipoproteinemia.
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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.
