Abetalipoproteinemia (ABL) and
familial hypobetalipoproteinemia (FHBL) are
genetic diseases characterized by
low density lipoprotein deficiency. ABL presents early in life with the gastroenterological manifestations of fat malabsorption,
steatorrhea, and
failure to thrive, and later in life, with progressive ophthalmopathy and neuropathy as a result of deficiency of the fat-soluble
vitamins A and E. Heterozygous FHBL subjects are usually asymptomatic, but may develop
fatty liver disease. In homozygous (compound heterozygous) FHBL, the clinical and biochemical features are indistinguishable from those of ABL and treatment recommendations are the same:
dietary fat restriction to prevent
steatorrhea, and long-term high-dose
vitamin E and A supplementation to prevent or at least slow the progression of neuromuscular and
retinal degenerative disease. Despite their low plasma
vitamin E levels, individuals with heterozygous FHBL do not require
vitamin E supplementation. There are conflicting reports on whether increased oxidative stress is seen in ABL; these differences may relate to the small size of patient groups as well as differences in patient age and dose of
vitamin E supplementation, or the contribution from dietary sources of
vitamin E.
High density lipoproteins in ABL appear to be severely oxidized yet able to inhibit platelet aggregation by binding to
scavenger receptor B1. We review the role of
vitamin E and oxidative stress in ABL and FHBL.