Because patients with abetalipoproteinemia are unable to secrete apolipoprotein B, they cannot normally transport lipids in their circulation and thus have depressed plasma concentrations of various lipophilic substances, including triglycerides, cholesterol, and fat-soluble vitamins (1, 2). Administration of vitamin A and water-soluble preparations of vitamin E has halted or slowed the progressive neurologic and retinal deterioration seen in patients with this disease (3-6). These beneficial effects occurred despite the inability of plasma vitamin E to return to normal levels (5). By evaluating plasma and hepatic levels of vitamins A and E in a patient with abetalipoproteinemia after she received replacement...