What Is Carnitine Palmitoyltransferase II Deficiency?
Carnitine Palmitoyltransferase II (CPT II) deficiency, caused by mutations in the CPT2 gene, is an inherited disease in which the body cannot convert long-chain fatty acids into energy to fuel the body. There are three forms of the disease, and the severity and symptoms vary based on the form. In all three forms, symptoms can be triggered by periods without eating (fasting).
Lethal Neonatal Form
The lethal neonatal form of CPT II deficiency is the most severe form of the disease. Symptoms begin within days of birth and include liver failure, respiratory failure, problems with the heart muscle (cardiomyopathy), irregular heartbeat (arrhythmia), kidney disease, and brain abnormalities. Affected infants tend to experience metabolic crises involving low blood sugar and low blood ketones (hypoketotic hypoglycemia). Most infants with the lethal neonatal form of CPT II will pass away within the first year.
Severe Infantile Hepatocardiomuscular Form
Symptoms of the severe infantile hepatocardiomuscular form of CPT II deficiency usually begin between the ages of six months and two years. They include an enlarged liver (hepatomegaly), problems with the heart muscle, irregular heartbeat, seizures, low blood sugar, abdominal pain, headache, and muscle weakness in the arms and legs. Severe episodes of metabolic crises can be triggered by periods without eating and illness. Infants with this form of CPT II deficiency are at risk for damage to their liver and brain, and they are at risk of coma or sudden death.
Mild Myopathic Form
The mild myopathic form of CPT II deficiency is the most-common and least-severe form of the disease. Symptoms can begin in childhood or adulthood. Individuals with the mild myopathic form of CPT II deficiency will experience episodes of muscle pain (myalgia) and muscle breakdown (rhabdomyolysis) as their primary symptom. Excessive muscle breakdown can also lead to kidney damage, resulting in potential kidney failure. Symptoms can be triggered by fasting, exercise, illness, and other forms of stress. Individuals with this form of CPT II deficiency typically do not experience symptoms between these episodes, though some will experience frequent muscle pain.
The mild myopathic form of CPT II deficiency is more common in men than women. Studies have shown the ratio of symptomatic men to women to be as high as five to one. The reason for this gender differential is not well understood.
How Common Is Carnitine Palmitoyltransferase II Deficiency?
CPT II deficiency is quite rare. The lethal neonatal form of CPT II has been reported in 13 families while the severe infantile hepatocardiomuscular form has been reported in 20 families. There are more than 200 reported cases of the mild myopathic form, but scientists believe the true incidence of the mild myopathic form of CPT II deficiency may be more common, due to some individuals having minimal symptoms.
How Is Carnitine Palmitoyltransferase II Deficiency Treated?
There is no cure for CPT II deficiency, and very little can be done to help infants and children with the lethal neonatal form and severe infantile hepatocardiomusclar form of the disease other than to treat symptoms as they arise and make the patients as comfortable as possible.
Individuals with the mild myopathic form of CPT II deficiency should avoid strenuous exercise, long periods without eating, and extreme temperatures. They are recommended to eat a modified diet that consists of frequent, high-carbohydrate, low-fat meals. Some doctors also suggest using carnitine supplements. During infection, individuals with CPT II deficiency may benefit from infusions of glucose. During episodes of muscle pain and muscle breakdown, individuals should drink plenty of fluids to prevent kidney damage.
In general, individuals with CPT II deficiency should avoid taking ibuprofen, valproic acid, and diazepam in high doses. They should also notify their physician before undergoing general anesthesia, as this can provoke an episode of muscle pain and weakness.
What Is the Prognosis for an Individual with Carnitine Palmitoyltransferase II Deficiency?
Infants with the lethal neonatal form of CPT II deficiency typically die within the first year of life.
Infants and children with the severe infantile hepatocardiomuscular form are susceptible to life-threatening heart problems and typically have shortened lifespans with numerous medical issues.
Individuals with the mild myopathic form of the disease typically have normal lifespans with episodes of muscle breakdown, sometimes leading to kidney damage. This form of the disease is usually manageable and allows for a near-normal quality of life.
Additional Considerations for Carriers
Carriers of fatty-acid oxidation defects, including CPT II deficiency, do not typically show symptoms of the disease. However, there may be an increased risk of serious pregnancy complications, particularly in the third trimester, in women carrying a fetus affected with a fatty-acid oxidation defect. A woman whose pregnancy may be affected by a fatty-acid oxidation defect, such as CPT II deficiency, should speak with her physician for recommendations and may benefit from consultation with a high-risk physician.