In a preceding paper, we described the molecular
biological defects in a patient with a severe form of the familial
lipoprotein disorder
type III hyperlipoproteinemia (HLP) and an unusual
apolipoprotein (
apo) E1 phenotype and epsilon 1/"null" genotype. The index case was a 60-year-old white male of German ancestry who suffered from a
myocardial infarction at age 50 years. He had distinctly elevated levels of plasma
lipids (
triglycerides 551 mg/dl and
cholesterol 747 mg/dl, respectively) and typical clinical signs of this inborn error of
lipoprotein metabolism. His mutant
apo E1 was shown to be identical to a rare (already described)
apo E1 (Gly127----Asp, Arg158----Cys) variant. A second independent defect at the molecular level was a
nucleotide deletion of a
guanosine (G) in the
codon for
amino acid 31 of the proband's apo epsilon 3 allele. This single base deletion (not described before) changed his apo epsilon 3 allele to a nonfunctional "null" allele devoid of a stable gene product. Here we describe the response to combined dietary and medical treatment of the patient with this unusual form of type III HLP. His response to
therapy was excellent, similar to patients with "classical" type III HLP and homozygosity for
apo E2. However, the correct diagnosis of this familial
lipoprotein disorder seems to be necessary, even in patients without the expected
apo E2/2 phenotype, in terms of the prompt and beneficial response to therapeutic interventions.