Carnitine palmitoyltransferase i deficiency

Carnitine Palmitoyltransferase I Deficiency

Carnitine palmitoyltransferase I deficiency (CPT I deficiency) is a rare metabolic disorder that affects the body's ability to convert certain fats into energy, particularly during periods without food (fasting). This condition is part of a group of disorders known as fatty acid oxidation disorders.

Pathophysiology

CPT I deficiency is caused by mutations in the CPT1A gene, which provides instructions for making an enzyme called carnitine palmitoyltransferase I. This enzyme is found in the outer membrane of mitochondria, the energy-producing centers in cells. It plays a crucial role in the oxidation of long-chain fatty acids by facilitating their transport into the mitochondria. In individuals with CPT I deficiency, the transport of long-chain fatty acids into the mitochondria is impaired, leading to an inability to produce energy from these fats.

Clinical Presentation

Symptoms of CPT I deficiency typically appear in infancy or early childhood and may include:

• Hypoketotic hypoglycemia (low blood sugar without the expected increase in ketones)
• Hepatomegaly (enlarged liver)
• Muscle weakness
• Lethargy
• Seizures

During fasting or illness, individuals with CPT I deficiency are at risk of metabolic crises, which can be life-threatening if not treated promptly.

Diagnosis

Diagnosis of CPT I deficiency is based on clinical symptoms, biochemical tests, and genetic testing. Biochemical tests may show:

• Low levels of ketones in the blood
• Elevated levels of free carnitine
• Abnormal acylcarnitine profile

Genetic testing can confirm the diagnosis by identifying mutations in the CPT1A gene.

Treatment

Management of CPT I deficiency involves dietary modifications and avoidance of fasting. Key aspects of treatment include:

• A high-carbohydrate, low-fat diet
• Frequent meals and snacks to prevent fasting
• Supplementation with medium-chain triglycerides (MCTs), which can be used as an alternative energy source

During illness or metabolic stress, intravenous glucose may be necessary to prevent hypoglycemia and metabolic crises.

Prognosis

With early diagnosis and appropriate management, individuals with CPT I deficiency can lead relatively normal lives. However, they must adhere to dietary restrictions and be vigilant about avoiding fasting and managing illnesses promptly.

Also see

• Fatty acid oxidation disorders
• Carnitine palmitoyltransferase II deficiency
• Medium-chain acyl-CoA dehydrogenase deficiency
• Metabolic disorder