Abstract
Familial hypobetalipoproteinemia (FHBL) is a rare co-dominant genetic disorder characterized by decrease of plasma low density lipoprotein-cholesterol (LDL-c) or apolipoprotein B (Apo-B) equal to or less than the 5th percentile for the population. We describe a 48-year-old male who presented with fatty liver disease (FLD), insulin resistance (IR), obesity and hypertension. Our patient thus met the latest diagnostic criteria of the metabolic syndrome (MS) proposed by the Adult Treatment Panel and the International Diabetes Federation. However, he had very low plasma concentration of LDL-c and Apo-B. DNA sequencing showed that he and two first-degree relatives affected by obesity and mild IR were heterozygous for a single nucleotide deletion on exon 15 of the APOB gene, which was predicted to form a truncated Apo-B designated Apo B-15.56.