SCIENTIFIC BACKGROUND

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ABCA1

Description

Tangier disease is a very rare autosomal recessive disorder of high-density lipoprotein (HDL) metabolism characterized by an absence of mature HDL particles in plasma and lipid deposits in various parenchymal organs. Characteristic features include orange hyperplastic tonsils, splenomegaly, and recurrent neuropathies. Biochemically, plasma is found to contain only pre-β-1-HDL andhas an almost complete absence of HDL cholesterol (<5 mg/dl), as well as low apoAI, low cholesterol, and normal or elevated triglycerides. Tangier disease patients have a moderately increased coronary risk.

The disease is caused by pathogenic variants in the ABCA1 gene (ATP-binding cassette transporter 1), a membrane protein involved in cholesterol and phospholipid efflux from the cell. Due to ABCA1 dysfunction, nascent HDL particles cannot take up sufficient cholesterol and phospholipids from peripheral cells and are rapidly metabolized. Other monogenic diseases that lead to HDL particle maturation dysfunction and are therefore associated with HDL deficiency (hypoalphalipoproteinemia) (HDL-C < 10 mg/dl) are lecithin-cholesterol acyltransferase (LCAT) deficiency, partial LCAT deficiency (fish eye disease), and apolipoprotein A-I (apo A-I) deficiency. Apo A-I deficiency is also associated with an increased risk of coronary heart disease (CHD).

References
Shapiro M.D. 2018, Endotext [Internet] / Hooper et al. 2017, EJHG 25:e1 / Schaefer et al. 2016, Prog. Cardiovasc. Dis. 59:97 / Ramasamy I. 2016, Clin Chim Acta. 454:143 / Schaefer et al. 2016, Endotext [Internet]