Carnitine palmitoyltransferase II deficiency, sometimes shortened to CPT-II or CPT2, is an autosomal recessively inherited genetic metabolic disorder characterized by an enzymatic defect that prevents long-chain fatty acids from being transported into the mitochondria for utilization as an energy source.

The infantile form involves multiple organ systems and is primarily characterized by hypoketotic hypoglycemia (recurring attacks of abnormally low levels of fat breakdown products and blood sugar) that often results in loss of consciousness and seizure activity.

[4] Muscle weakness and pain typically resolves within hours to days, and patients appear clinically normal in the intervening periods between attacks.

Symptoms are most often exercise-induced, but fasting, a high-fat diet, exposure to cold temperature, sleep deprivation, or infection (especially febrile illness) can also provoke this metabolic myopathy.

In a minority of cases, disease severity can be exacerbated by three life-threatening complications resulting from persistent rhabdomyolysis: acute kidney failure, respiratory insufficiency, and episodic abnormal heart rhythms.

[citation needed] In addition to similarities shared by the acyltransferases, CPT II also contains a distinct insertion of 30 residues in the amino domain that forms a relatively hydrophobic protrusion composed of two alpha helices and a small anti-parallel beta sheet.

The catalytic core of the CPT II enzyme contains three important binding sites that recognize structural aspects of CoA, palmitoyl, and carnitine.

[11] The majority of the genetic abnormalities in CPT II deficient patients affect amino acid residues somewhat removed from the active site of the enzyme.

[6] Two groups[14][15] have recently reported a limited correlation (lacking in statistical significance) between the genotypic array and the clinical severity of the phenotype in their patient cohorts.

[16] This group concluded that both the type and location of CPT2 mutation in combination with at least one secondary genetic factor modulate the long-chain fatty acid flux and, therefore, the severity of the disease.

[16] Carnitine is a hydrophilic natural substance acquired mostly through dietary meats and dairy products and is used by cells to transport hydrophobic fatty acids.

[14] To date, sixty disease-causing mutations within the coding sequence of CPT2 have been reported in the literature, of which 41 are thought to result in amino acid substitutions or deletions at critical residues.

[14] Standard of care for treatment of CPT II deficiency commonly involves limitations on prolonged strenuous activity and the following stipulations: This article incorporates public domain text from The U.S. National Library of Medicine