Fatty acid β-oxidation defects

Inherited fatty acid oxidation disorders (FAOD) are among the most common inborn errors of metabolism. The spectrum of clinical phenotypes associated with FAOD is wide, correlates to the severity of the specific enzyme deficiency, and includes cardiomyopathy, fasting or illness-induced hypoketotic hypoglycemia, or recurrent rhabdomyolysis, generally triggered by exercise or febrile illness. Diagnosis is accomplished through specialized biochemical analysis followed by either measurement of specific enzyme activity or more commonly molecular analysis of disease-associated genes. Newborn screening detects the majority of but not all infants with FAOD and frequently allows treatment initiation prior to symptom onset. Avoidance of extreme fasting prevents hypoglycemia and is life saving for at risk infants. Restriction of dietary fat intake and replacement with medium chain triglyceride (MCT) oil to provide a usable energy substrate may also be included in the treatment of individuals with defects in long chain fatty acid oxidation. Long term outcomes for many FAOD are generally satisfactory once a diagnosis has occurred and steps to avoid episodes of metabolic decompensation have been taken. However, chronic complications of peripheral neuropathy or pigmentary retinopathy associated with vision loss may occur in specific disorders of long chain FAOD despite dietary therapy.