Carnitine palmitoyltransferase II deficiency, which is also known as CPT II deficiency, is an inherited inborn error of metabolism (IEM) of fatty acid oxidation leading to muscle weakness. It is the most common inherited disorder of lipid metabolism affecting the skeletal muscle of adults. It is an autosomal recessive disorder associated with a mutation in the enzyme carnitine palmitoyltransferase II. Carnitine palmitoyltransferase II (CPT2) is a peripheral inner mitochondrial membrane protein found in all tissues that oxidize fatty acids. It catalyzes the transesterification of palmitoylcarnitine back into palmitoyl-CoA which is a substrate for beta-oxidation inside the mitochondrial matrix. CPT2 is responsible for the formation of acylcarnitines by catalyzing the transfer of the acyl group of a long-chain fatty acyl-CoA from CoA to carnitine. Carnitine, a natural substance acquired mostly through the diet, is used by cells to process fats and produce energy. Deficiencies or mutations in the CPT2 gene lead to disorders of long-chain fatty acid oxidation. There are three forms of CPT II deficiency: (1) lethal neonatal form, (2) severe infantile hepatocardiomuscular form, and (3) the myopathic form. More than 300 CPT II deficiency cases have been described with the myopathic form being the most common (myopathic form: 86%, severe infantile form: 8%, neonatal form: 6% of cases). The myopathic form is usually mild and can manifest from infancy to adulthood. The infantile and neonatal forms are severe multisystemic diseases characterized by liver failure with hypoketotic hypoglycemia, cardiomyopathy, seizures, and early death. The adult-onset myopathic form is characterized by exercise-induced muscle pain and weakness, sometimes associated with myoglobinuria. The most common cause of hereditary myoglobinuria is the myopathic form of CPT II deficiency and affects men more than women.
References
Carnitine Palmitoyl Transferase Deficiency II References
Wieser T: Carnitine Palmitoyltransferase II Deficiency
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