Muscle carnitine palmitoyltransferase (CPT) II deficiency is an autosomal recessive disorder of fatty acid oxidation characterized by attacks of myalgia and myoglobinuria. This review summarizes the clinical features of this disease, analyzing data of 28 patients with biochemically and genetically confirmed CPT II deficiency. The review shows that exercise-induced myalgia is the most frequent symptom, whereas myoglobinuria, known as the clinical hallmark, is missing in 21% of the patients. Typically, myalgia starts in childhood, whereas attacks with myoglobinuria mostly emerge in adolescence or early adulthood. However, there are also patients with only myalgia, patients with attacks triggered by factors other than exercise, and patients with late-onset disease. Molecular or biochemical analysis is necessary for diagnosis, since no myopathologic hallmark exists. For screening patients, analysis of not only the common S113L mutation but also the P50H and Q413fs-F448L mutations is recommended. The phenotype of muscle CPT II deficiency might be influenced by the underlying mutation, and patients with a truncating mutation on 1 allele might be affected more severely.
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