CPT-II deficiency is inherited in an autosomal recessive pattern. Normally a person has two functional CPT-2 genes. In people with CPT-II deficiency, both genes have a mutation and there is a deficiency of the critical enzyme activity. Each parent of a newborn with CPT-II deficiency typically has one functional and one mutated gene and is considered a carrier. When both parents are carriers, the chance of a newborn inheriting two mutated genes is 25%.
Carriers of CPT-II deficiency do not typically have symptoms.
There are three types of CPT-II: neonatal, severe infantile and myopathic.
Neonatal: The neonatal form is lethal and appears in the first few days of life. Symptoms include respiratory distress, liver failure, hypoketotic hypoglycemia (low ketones and low blood sugar), cardiomyopathy (heart muscle disease) and seizures.
Severe infantile: Infants with severe CPT-II deficiency typically have liver failure, hypoketotic hypoglycemia (low ketones and low blood sugar), cardiomyopathy (heart muscle disease) and seizures. The symptoms begin within the first year of life.
Myopathic: The symptoms of this form of CPT-II deficiency can begin anytime during the lifespan. Symptoms include muscle pain and weakness due to extensive exercise, physical stress or illness and myoglobinuria (myoglobin in the urine).
- Incidence: CPT-II deficiency is rare. There have been less than 50 patients with the severe infantile and neonatal form reported in the literature. Although more common than the early onset forms, the myopathic form is still very rare, and has been reported in less than 500 people.
- New York State Method of Screening (First Tier): Screening for CPT-II deficiency is accomplished by measuring acylcarnitines (C16 and C18:1) by tandem mass spectrometry (MS/MS), in combination with a low value for the ratio of C0/(C16+C18:1).
- Second Tier Screening: None
- Testing can be affected by: Screening may be normal in patients who received IV glucose or who were not ill when the specimen was collected. Newborn screening cannot distinguish CPT-II from carnitine acylcarnitine translocase (CAT) deficiency.
- Interpretation/reporting of data: Results are reported as screen negative or as a referral. Prompt consultation with a specialist is required for a referral.
- Referral to Specialty Care Center: Patients with an abnormal newborn screen for CPT-II deficiency are referred to an Inherited Metabolic Disorder Specialty Care Center for evaluation by a biochemical geneticist trained in the diagnosis and treatment of CPT-II deficiency.
Diagnostic testing may include an acylcarnitine profile, CPT-2 enzyme analysis and molecular genetic analysis of the CPT-2 gene.
Treatment is dietary, including avoidance of fasting, a high-carbohydrate, low fat diet and carnitine supplementation. During times of illness, hospitalization may be required to monitor and treat hypoglycemia.
Prognosis is poor for the neonatal and severe infantile forms. For the myopathic form, prognosis is variable and dependent on multiple factors, including the severity of disease and response to treatments.
Carnitine palmitoyltransferase 2 (CPT-II) deficiency is a fatty acid oxidation disorder (inherited metabolic disorder).
CPT-II deficiency is caused by mutations in the CPT-2 gene. Individuals with this disorder are unable to convert certain fats to energy and may develop symptoms during times of high energy need such as fasting or illness.