Carnitine Acylcarnitine Translocase Deficiency

Definition

Definition of Carnitine Acylcarnitine Translocase Deficiency
Carnitine-acylcarnitine translocase (CACT) deficiency is a condition that prevents the body from using certain fats for energy, particularly during periods without food (fasting). Signs and symptoms of this disorder usually begin soon after birth and may include breathing problems, seizures, and an irregular heartbeat (arrhythmia). Affected individuals typically have low blood sugar (hypoglycemia) and a low level of ketones, which are produced during the breakdown of fats and used for energy. Together these signs are called hypoketotic hypoglycemia. People with CACT deficiency also usually have excess ammonia in the blood (hyperammonemia), an enlarged liver (hepatomegaly), and a weakened heart muscle (cardiomyopathy).

Symptoms

Symptoms of Carnitine Acylcarnitine Translocase Deficiency
The signs of carnitine-acylcarnitine translocase deficiency usually begin within the first few hours of life. Seizures, an irregular heartbeat, and breathing problems are often the first signs of this disorder. This disorder may also cause extremely low levels of ketones (products of fat breakdown that are used for energy) and low blood sugar (hypoglycemia). Together, these two signs are called hypoketotic hypoglycemia. Other signs that are often present include ammonia in the blood (hyperammonemia), an enlarged liver (hepatomegaly), heart abnormalities (cardiomyopathy), and muscle weakness. This disorder can cause sudden infant death.

Causes

Causes of Carnitine Acylcarnitine Translocase Deficiency
CAT deficiency occurs when an enzyme, called "carnitine acylcarnitine translocase" (CAT), is either missing or not working properly. This enzyme's job is to help change certain fats in the food we eat into energy. It also helps to break down fat already stored in the body.

Energy from fat keeps us going whenever our bodies run low of their main source of energy, a type of sugar called glucose. Our bodies rely on fat for energy when we don't eat for a stretch of time - like when we miss a meal or when we sleep.

Diagnosis

Diagnosis of Carnitine Acylcarnitine Translocase Deficiency
Newborn screening of a dried blood spot using tandem mass spectrometry reveals elevations of several long-chain acylcarnitines (i.e. C16, C18, C18:1 and C18:2). These findings are characteristic but not definitive of CACT Deficiency, because Carnitine Palmitoyl Transferase II Deficiency has similar results. Quantitative urine organic acid determination is usually not helpful, as elevations of long chain fatty acids, including dicarboxylic and 3-hydroxy-dicarboxylic acids are inconsistently present. Plasma acylcarnitine profile testing can confirm elevations of the above acylcarnitines. Definitive diagnosis of CACT Deficiency requires testing cultured fibroblasts or performing DNA mutation analysis of the gene. Prenatal diagnosis can be accomplished using DNA analysis if mutations are identified in the parents.

Treatment

Treatment of Carnitine Acylcarnitine Translocase Deficiency
Your baby’s primary doctor will work with a metabolic doctor to care for your child. Your doctor may also suggest that you meet with a dietician familiar with CAT deficiency.

Certain treatments may be helpful for some children but not others. When necessary, treatment usually needed throughout life. The following are treatments sometimes recommended for children with CAT deficiency:

1.  Avoid going a long time without food : Infants and young children with CAT deficiency need to eat frequently to prevent a metabolic crisis. Your metabolic doctor will tell you how often your child needs to be fed.  In general, it is often suggested that infants be fed every four to six hours. Some babies need to eat even more frequently than this. It is important that infants be fed during the night. They may need to be woken up to eat if they do not wake up on their own. Your metabolic doctor and dietician will give you an appropriate feeding plan for your infant. Your doctor will also give you a ‘sick day’ plan, tailored to your child’s needs, for you to follow during illnesses or other times when your child will not eat.

2. Diet : Sometimes a low-fat, high carbohydrate diet is advised. Carbohydrates give the body many types of sugar that can be used as energy. In fact, for children needing this treatment, most food in the diet should be carbohydrates (bread, pasta, fruit, vegetables, etc.) and protein (lean meat and low-fat dairy food). Any diet changes should be made under the guidance of a dietician. People with CAT deficiency cannot use particular building blocks of fat called "long chain fatty acids". A dietician can help you create a food plan low in these fats. Any diet changes should be made under the guidance of a dietician experienced with CAT deficiency.

3. L-carnitine and MCT oil : Some children may be helped by taking L-carnitine. This is a safe and natural substance that helps body cells make energy. It also helps the body get rid of harmful wastes. Your doctor will decide whether or not your child needs L-carnitine. Unless you are advised otherwise, use only L-carnitine prescribed by your doctor. Do not use L-carnitine without checking with your doctor.

Medium Chain Triglyceride oil (MCT oil) is sometimes used as part of the food plan for people with CAT deficiency. This special oil has medium chain fatty acids that people with CAT deficiency can use in small amounts for energy. Your metabolic doctor or dietician can guide you in how to use this supplement. You will need to get a prescription from your doctor to get MCT oil.

Prognosis

Prognosis of Carnitine Acylcarnitine Translocase Deficiency
Consult with your doctor.

Prevention

Prevention of Carnitine Acylcarnitine Translocase Deficiency
Consult with your doctor.