Carnitine palmitoyltransferase II deficiency

Carnitine palmitoyltransferase II (CPT II) deficiency is a condition that prevents the body from using certain fats for energy, particularly during periods of fasting. There are three main types of CPT II deficiency that vary in severity and the age at which symptoms first appear: a lethal neonatal form, a severe infantile hepatocardiomuscular form, and a myopathic form.

The lethal neonatal form of CPT II deficiency becomes apparent soon after birth. Infants with this form of the disorder develop respiratory failure, liver failure, a weakened heart muscle (cardiomyopathy), and an irregular heartbeat (arrhythmia). In many cases, the brain and kidneys are also structurally abnormal. Affected individuals have low levels of glucose in the blood and low levels of ketones, which are produced during the breakdown of fats and used for energy. Together, these signs are called hypoketotic hypoglycemia. If affected individuals fast for long periods of time, they can experience seizures or coma. Because of these serious health complications, infants with the lethal neonatal form of CPT II deficiency usually live for only a few days to a few months.

The severe infantile hepatocardiomuscular form of CPT II deficiency affects the liver, heart, and muscles. Signs and symptoms usually appear within the first year of life. This form involves recurring episodes of hypoketotic hypoglycemia, seizures, liver dysfunction, cardiomyopathy, arrhythmia, and muscle weakness (myopathy) in the arms and legs. Signs and symptoms of this form of CPT II deficiency can be triggered by fasting or by illnesses such as viral infections. Individuals with the severe infantile hepatocardiomuscular form of CPT II deficiency are at risk for liver failure, nervous system damage, coma, and sudden death.

The myopathic form is the least severe type of CPT II deficiency. This form is characterized by recurrent episodes of muscle pain (myalgia) and occasional weakness that is associated with the breakdown of muscle tissue (rhabdomyolysis). The destruction of muscle tissue releases a protein called myoglobin. This excess myoglobin may cause urine to be red or brown (myoglobinuria). Episodes of myalgia and rhabdomyolysis may be triggered by exercise, stress, exposure to extreme temperatures, infections, or fasting. The first episode of myalgia usually occurs during childhood or adolescence. The severity and frequency of episodes varies among affected individuals. Most people with the myopathic form of CPT II deficiency have no signs or symptoms of the disorder between episodes.

People with CPT II deficiency are often encouraged to avoid triggers such as long periods of fasting and intensive exercise to limit the occurrence of serious health problems.

CPT II deficiency is often detected shortly after birth by newborn screening, which identifies abnormal levels of certain compounds in the blood. In individuals with CPT II deficiency, the blood levels of certain fats are elevated.