Identifies a specific genetic mechanism (compound heterozygous APOB mutations) causing normotriglyceridemic hypobetalipoproteinemia and chronic vitamin E deficiency.
May prompt genetic testing in unexplained vitamin E deficiency; leaves open broader phenotypic correlations.
A 12-year-old boy with mental retardation, obesity, ataxia, and visual impairment was shown to have normal fasting plasma triglyceride but low cholesterol and vitamin E levels. Investigations indicated that he was compound heterozygous for two mutations in the apolipoprotein B gene (APOB), resulting in a failure to express apolipoprotein B-100, yet retain apolipoprotein B-48 production. The proband therefore was able to form chylomicrons, but not a low-density lipoprotein capable of receptor-mediated endocytosis. This resulted in chronic vitamin E deficiency. We suggest the term normotriglyceridemic hypobetalipoproteinemia for this easily recognizable condition.
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Homer et al. (2005) studied this question.
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