Carnitine palmitoyltransferase II (CPT II) deficiency impairs the body’s ability to convert long-chain fatty acids into energy for its functions.
CPT II deficiency presents in three distinct forms, each varying in severity and symptoms. All three forms can be triggered by fasting periods.
Lethal Neonatal Form: The most severe variant of CPT II deficiency, it manifests within days of birth. Symptoms include liver and respiratory failure, cardiomyopathy, arrhythmias, kidney issues, and brain abnormalities. Metabolic crises involving low blood sugar and ketones (hypoketotic hypoglycemia) are common. Unfortunately, most infants with this form do not survive beyond the first year.
Severe Infantile Hepatocardiomuscular Form: Symptoms typically emerge between six months and two years of age and encompass hepatomegaly, heart muscle problems, irregular heartbeats, seizures, low blood sugar, abdominal pain, headaches, and limb muscle weakness. Metabolic crises can occur during fasting and illness, risking liver and brain damage, as well as coma or sudden death.
Mild Myopathic Form: This is the most common and least severe form, with symptoms arising in childhood or adulthood. Individuals with this form primarily experience muscle pain (myalgia) and muscle breakdown (rhabdomyolysis). Excessive muscle breakdown may lead to kidney damage and potential kidney failure. Symptoms can be triggered by fasting, exercise, illness, or stress, with symptom-free intervals between episodes. This form is more prevalent in men than women, with a ratio of up to five to one, although the reason for this gender difference remains unclear.
CPT II deficiency is caused by pathogenic (disease-causing) variants in the CPT2 gene and exhibits autosomal recessive inheritance. This means that both parents must be carriers to have a 25% chance to have a child with the condition. The risk of being a carrier is based on a person’s ancestry or ethnic background. For example, individuals of Ashkenazi Jewish descent have a 1 in 45 chance to be a carrier.
CPT II deficiency carriers 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.
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Revised September 2023
