MTTP and autosomal recessive disease: ABL is a rare autosomal recessive disease characterized by markedly low levels of LDL-c, triglycerides and apoB, caused by loss-of-function (LOF) alterations in the Microsomal Triglyceride Transfer Protein (MTTP) gene that result in truncated forms of the coded protein (Wetterau et al., 1992; Hooper et al., 2005).