We found a heterozygous variant OSBPL1A p.C39X in subjects with high-density-lipoprotein cholesterol (HDL-C) <1st percentile.

Sera of the carriers displayed a reduced capacity to act as acceptors for cholesterol efflux.

Fibroblasts from a p.C39X carrier showed reduced cholesterol efflux to lipid-free apoA-I.

GFP-OSBPL1A-39X protein remained cytosolic and failed to bind Rab7, the receptor of OSBPL1A on late endosomes/lysosomes.

This is the first report on a human OSBPL1A mutation, and suggests that rare OSBPL mutations may contribute to dyslipidemias.