D-bifunctional protein (DBP) deficiency is an autosomal recessive inborn error of peroxisomal fatty acid oxidation. DBP is a homodimeric enzyme with 79-kDa subunits, each of which consists of three functional units. And it catalyzes the second and third steps of peroxisomal beta-oxidation of fatty acids. The biochemical hallmark of this disorder is the accumulation of very long-chain fatty acids (VLCFA), 2-methyl branched-chain fatty acids, and the bile acid intermediates (DHCA/THCA). The clinical presentation is very severe, and most affected children die within the first 2 years of life. Virtually all patients present with neonatal hypotonia and seizures.
