VLCAD, a key enzyme in the first step of mitochondrial fatty acid β-oxidation, catalyzes the dehydrogenation of lipid acyl coenzyme A from carbon chains of different lengths containing 14 to 18 carbons, with the coenzyme flavin adenine dinucleotide (FAD), which receives the hydrogen atoms generated by dehydrogenation and enters the mitochondrial respiratory chain for oxidative phosphorylation to produce ATP. VLCAD is expressed in mitochondria of liver, cardiac muscle, skeletal muscle, and skin fibroblasts, and catalyzes the production of long-chain esteryl coenzyme A to produce allyl coenzyme A. The process of β-oxidation of long-chain fatty acids is completed by the action of three enzymes: allyl coenzyme A hydratase, hydroxyesteryl CoA dehydrogenase, and ketoesteryl CoA sulfurylase, each producing one acetyl Acetyl coenzyme A can participate in the tricarboxylic acid cycle for oxidative phosphorylation for energy supply, and can also form ketone bodies in the liver to produce energy under exercise, starvation, stress, etc. VLCAD deficiency will lead to impaired metabolism of long-chain fatty acids in the body, and long-chain fatty acids cannot be oxidized for energy supply, and at the same time accumulate in the cells to produce toxic effects on the heart muscle, skeletal muscle, liver, etc., resulting in VLCADD has a series of clinical symptoms and signs. The prevalence of VLCADD is uncertain, and tandem mass spectrometry newborn screening for VLCADD using myristoyl carnitine (C14:1) as a newborn screening indicator has shown significant differences in prevalence between countries: an estimated 1/31,500 in Australia, 1/125,000 in Germany, and 1/42,500 in the U.K. Lindner et al. counted approximately 5,250,000 newborns in Australia, Germany, and the U.S. The incidence of VLCADD was estimated to be about 1/85,000 by Lindner et al. in a tandem mass spectrometry screening of 278775 newborns at the Shanghai Institute of Pediatric Medicine, and no patients with VLCADD were found in a tandem mass spectrometry screening of 102,200 newborns in Japan by Shigematsu Y et al. This suggests that the disease is rare in Asian countries. However, Tanmoki et al. found 8 cases of VLCADD (12.5%) among 64 cases of fatty acid oxidation disorders detected in 187 large medical institutions in Japan between 1985 and 2000, 3 cases of VLCADD (23.1%) among 13 cases of fatty acid oxidation disorders detected in a screening of 3070 patients at high risk for genetic metabolic diseases at the Shanghai Institute of Pediatric Medicine, and a total of 83 cases of fatty acid oxidation disorders detected subsequently. Of the 83 cases of fatty acid oxidation disorders, 11 cases were VLCADD (13.3%).