Purpose of review
Our purpose is to review recent publications in the area of marked human HDL deficiency, HDL particles, coronary heart disease (CHD), amyloidosis, the immune response, and kidney disease.
Lack of detectable plasma apolipoprotein (apo) A-I can be due to DNA deletions, rearrangements, or nonsense or frameshift mutations within the APOA1 gene resulting in a lack of apoA-I secretion. Such patients have marked HDL deficiency, normal levels of triglycerides and LDL cholesterol, and can have xanthomas and premature CHD. ApoA-I variants with amino acid substitutions, especially in the region of amino acid residues 50–93 and 170–178, have been associated with amyloidosis. Patients with homozygous Tangier disease have defective cellular cholesterol efflux due to mutations in the adenosine triphosphate-binding cassette transporter A1, detectable plasma apoA-I levels and preβ-1 HDL in their plasma. They have decreased LDL cholesterol levels and can develop neuropathy and premature CHD. Patients with lecithin: cholesterol acyltransferase deficiency have both preβ-1 and α-4 HDL present in their plasma and develop corneal opacities, anemia, proteinuria, and kidney failure.
Patients with marked HDL deficiency can have great differences in their clinical phenotype depending on the underlying defect.