Carnitine Palmitoyltransferase II (CPT2) deficiency is the most common defect of mitochondrial fatty acid oxidation. Three clinical phenotypes have been described. The most common type, described in over 200 cases, is the myopathic (or adult-onset) form characterized by recurrent attacks of myalgia accompanied by myoglobinuria (triggered by exercise, fasting, cold exposure or stress), possible weakness during attacks and usually no signs of myopathy between attacks, with onset between the first and sixth decade. For reasons currently unknown, the majority (~80%) of myopathic form patients are males. The severe infantile form of CPT2 has been described as liver failure, cardiomyopathy, seizures, hypoketotic hypoglycemia, peripheral myopathy and attacks of abdominal pain and headache with onset in the first year of life. A lethal neonatal form has been identified and is characterized by dysmorphic features (cystic renal dysplasia and neuronal migration defects) along with the symptoms of the infantile form, with death usually occurring within the first month.