APOA1 and Tangier disease: ABCA1 has been identified as a pivotal gene in the regulation of plasma HDL cholesterol levels and cellular cholesterol homeostasis, and it is defective in Tangier disease patients, an HDL deficiency.17–19 The interaction between ABCA1 and apoA‐I leads to the lipidation of apoA‐I, which then forms the nascent pre‐β (pre‐β1) HDL particle, an important initial step for reverse cholesterol transport.20