Carnitine palmitoyltransferase II deficiency

Carnitine palmitoyltransferase II (CPT II) deficiency is a rare inherited disorder of long-chain fatty acid oxidation caused by mutations in the CPT2 gene. The CPT II enzyme is located on the inner mitochondrial membrane and is essential for transporting long-chain fatty acids into the mitochondria, where they are broken down to produce energy. When this enzyme is deficient or dysfunctional, the body cannot properly use long-chain fats as an energy source, particularly during periods of fasting, illness, or prolonged exercise. Three clinical forms are recognized. The most common is the myopathic (adult) form, which typically presents in adolescence or young adulthood with recurrent episodes of muscle pain (myalgia), muscle stiffness, and rhabdomyolysis (breakdown of muscle tissue) triggered by prolonged exercise, fasting, cold exposure, infection, or emotional stress. Rhabdomyolysis can lead to myoglobinuria (dark-colored urine) and, in severe cases, acute kidney failure. The severe infantile hepatocardiomuscular form presents in the first year of life with liver failure, cardiomyopathy, hypoketotic hypoglycemia, and seizures, and is often fatal. The lethal neonatal form is the most severe, presenting at birth with multiple organ failure, brain and kidney malformations, cardiomyopathy, and is usually fatal within days to months. Treatment focuses on prevention and supportive care. For the myopathic form, management includes avoidance of known triggers such as prolonged fasting, intense or sustained exercise, and cold exposure. A diet high in carbohydrates and low in long-chain fats, with supplementation of medium-chain triglycerides (MCT oil), is recommended to provide an alternative energy source. Adequate hydration and prompt medical attention during episodes of rhabdomyolysis are critical to prevent kidney damage. For the infantile and neonatal forms, treatment is largely supportive, and outcomes remain poor despite intervention. Newborn screening programs in some regions can identify affected individuals through acylcarnitine profiling.

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