SLC25A20 gene

Also known as: CACT deficiency


1. The disease:

Carnitine-acylcarnitine translocase (CACT) deficiency is a life-threatening, inherited disorder of fatty acid oxidation, which usually presents in the neonatal period with severe hypoketotic hypoglycemia, hyperammonemia, cardiomyopathy and/or arrhythmia, hepatic dysfunction, skeletal muscle weakness, and encephalopathy.

2.The symptoms:

Most patients with CACT deficiency have a severe phenotype presenting within the first 48 hours of life as hypoketotic hypoglycemia, hyperammonemia, cardiomyopathy and arrhythmias, skeletal muscle damage, liver dysfunction and hypothermia. Neurological involvement with encephalopathy, epilepsy and developmental delay can also be described. Some patients can present as a sudden infant death (SIDS). A rare milder phenotype presenting in infancy/early childhood is also described that manifests with episodes of hypoketotic hypoglycemia and hyperammonemia often precipitated by fasting and/or intercurrent illness. Lack of early signs or symptoms does not exclude the diagnosis.

3. Actions to take in case of early diagnosis

  • Infants with a positive genetic test (having 2 pathogenic variants or 2 copies of a single pathogenic variant in the SLC25A20 gene) should continue breastfeeding and AVOID FASTING. Early treatment is crucial in preventing chronic symptoms.
  • Biochemical correlation is essential for confirming diagnosis with blood acylcarnitine analysis shows a very high acyl fraction with marked increase in C16, C18, and C18:1 species. Free carnitine is very low. Biochemical NBS with tandem mass spectrometry can also help.
  • CACTD is a lifelong disease that requires lifetime management and regular follow-up with a metabolic physician and a multidisciplinary approach to care.
  • During an acute episode, intravenous glucose is administered in order to inhibit lipolysis.
  • Strict avoidance of fasting along with the institution of a low long-chain fat diet and medium chain triglyceride (MCT) supplementation is necessary. However, the MCT formula should be as low as possible in C10 and C12 fatty acids as high dietary intake of these can lead to decompensation. Carnitine supplementation is also recommended.
  • Genetic counseling is highly recommended for family planning and evaluation of at-risk family members such as siblings.

4. For more information