Clinical Guidance
Long-chain hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency and trifunctional protein (TFP) deficiency are caused by impairment of mitochondrial TFP. TFP has three enzymatic activities – long-chain enoyl-CoA hydratase, long-chain 3-hydroxyacyl-CoA dehydrogenase, and long-chain 3-ketoacyl-CoA thiolase. Deficiency of the enzyme long-chain 3-hydroxyacyl-CoA dehydrogenase occurs in individuals with LCHAD deficiency, while deficiency of all three enzymes occurs in individuals with TFP deficiency. LCHAD and TFP deficiency are disorders of long-chain fatty acid oxidation, which typically present with recurrent episodes of hypoketotic hypoglycemia precipitated by fasting or illness. In addition, the other characteristic manifestations of long-chain fatty acid oxidation defects (FAODs) such as cardiomyopathy, liver dysfunction, or rhabdomyolysis may be present. However, peripheral neuropathy and retinopathy are unique complications of these disorders not seen in other FAODs. The clinical presentation represents a continuous spectrum of severity ranging from severe neonatal-onset to mild late-onset forms. Individuals with LCHAD deficiency usually present with a severe-to-intermediate phenotype, while individuals with TFP deficiency typically present with a severe-to-mild phenotype. Table 2. LCHAD/TFP Deficiency: Frequency of Select Features
