Carnitine transporter defect (CTD)

Alternative names
  • Systemic or primary carnitine deficiency
  • Carnitine uptake defect
  • Deficiency of plasma-membrane carnitine transporter
About the condition CTD is a fatty acid oxidation disorder. It is a hereditary disease that is caused by a missing protein needed to reabsorb carnitine in the kidney. The features of the condition are caused by intracellular carnitine deficiency, which is needed to convert fat into energy.
Inheritance Autosomal recessive
Year screening started in WA 2005 
Incidence in WA Approximately 1 in 40,000 births
Defect Caused by defects in the SLC22A5 gene, which encodes the carnitine transporter OCTN2.
Symptoms if untreated
  • Hypoketotic hypoglycaemia
  • Vomiting, lethargy, seizures and coma
  • Hepatomegaly
  • Cardiomyopathy
  • Skeletal myopathy
Metabolites on bloodspot screening
  • Decreased free carnitine (C0)
  • Decreased long-chain acylcarnitines (C16 and C18)
Diagnostic tests
  • Plasma carnitine
  • Plasma acylcarnitine profile
  • Urine carnitine fractional excretion
  • SLC22A5 gene analysis
Treatment
  • Carnitine supplementation
  • Avoidance of fasting
Screening issues
  • Some children with CTD may be asymptomatic
  • Maternal CTD deficiency may be detected incidentally