Long Chain Acyl CoA Dehydrogenase (LCAD) deficiency is a rare inherited disorder of fatty acid metabolism. It was believed that this effect was due to deficiency of LCAD, one of the enzymes that carry out the initial step of beta oxidation of fatty acids. However, of late, it is becoming increasingly clear that the defect involves the VLCAD (Very Long Chain Acyl CoA Dehydrogenase) enzyme, and that all cases believed to be LCAD deficiencies, are actually those of VLCAD Deficiencies. The condition causes accumulation of toxic long chain acyl Co-A intermediates in the mitochondria. These toxic metabolites impair normal mitochondrial functioning including gluconeogenesis, glycogenolysis, and ureagenesis. Thus, affected patients tend to become hypoglycemic upon the slightest amount of stress, and may often go into hypoglycemic coma, are hypoketotic, and have low plasma and tissue carnitine levels.

Diagnostic findings include low LCAD activity, elevated serum urea, uric acid, creatinine phosphokinase, and urinary long and medium chain dicarboxylic acids, and low urinary ketones. LCAD deficiency is a chronic disease and needs life long management. There is no cure for the condition. The goal of management is to avoid acute episodes and manage diet so as to prevent a hypoglycemic condition. Carnitine may be supplied to circumvent the carnitine deficiency associated with this disorder.

LCAD is one of the four enzymes, along with SCAD, MCAD, and VLCAD, that catalyze the alpha, beta dehydrogenation of acyl Co A, which is the first step in the beta oxidation of fatty acids. LCAD can catalyze the oxidation of branched as well as straight chain fatty acids and also, some mono unsaturated acyl Co As. It was understood that mutations in the LCAD gene was what cause LCAD Deficiency. However, recent studies have revealed that affected patients have normal cDNA levels of LCAD, but have deficient activity or absence of the VLCAD enzyme, suggesting that the condition is actually a VLCAD Deficiency.