Homozygous familial hypercholesterolemia, also known as Autosomal recessive hypercholesterolemia (ADH), is characterized by high levels of low-density lipoprotein (LDL) cholesterol, and associated with premature cardiovascular disease and myocardial infarction. Approximately 1:500 individuals worldwide are affected by ADH. Most ADH is caused by genetic variants leading to decreased intracellular uptake of cholesterol. The majority of these cases have familial hypercholesterolemia (FH), which is due to mutations in the LDLR gene, which encodes for the LDL receptor. Approximately 15% of ADH cases have familial defective apolipoprotein B-100 (FDB) due to mutations in the LDL receptor-binding domain of the APOB gene, which encodes for apolipoprotein B-100.