Carnitine Uptake Defect (CUD)
CUD is inherited in an autosomal recessive pattern. Normally a person has two functional SLC22A5 genes. In people with CUD, both genes have a mutation and there is a deficiency of the critical protein. Each parent of a newborn with CUD typically has one functional and one mutated gene and is considered a carrier. When both parents are carriers, the chance of a newborn inheriting two mutated genes is 25%.
Carriers of CUD do not typically have symptoms.
The symptoms are extremely variable. Some people with CUD never develop symptoms. In some children, symptoms may begin in infancy or early childhood and include cardiac (heart) symptoms (cardiomyopathy), irritability, lethargy, hepatomegaly (enlarged liver) and intermittent hypoglycemia (low blood sugar). Symptoms may also begin in early childhood (myopathy and cardiomyopathy) or adulthood (chronic fatigue). Myopathy is a muscle disease.
- Incidence: The overall incidence is approximately 1 in 100,000.
- New York State Method of Screening (First Tier): Screening for CUD is accomplished by measuring total acylcarnitines and free carnitine by tandem mass spectrometry (MS/MS).
- Second Tier Screening: None
- Testing can be affected by: Maternal CUD
- Interpretation/reporting of data: Results are reported as within acceptable limits, borderline or as a referral. A repeat specimen should be collected for a borderline result. Prompt consultation with a specialist is required for a referral.
- Referral to Specialty Care Center: Patients with an abnormal newborn screen for CUD are referred to an Inherited Metabolic Disorder Specialty Care Center for evaluation by a biochemical geneticist trained in the diagnosis and treatment of CUD.
Diagnostic testing includes quantification of plasma acylcarnitines and molecular genetic testing of the SLC22A5 gene. Testing may also include carnitine transport studies on fibroblasts (skin cells).
Treatment is carnitine supplementation.
Prognosis is good as long as carnitine supplementation is taken.
Carnitine uptake defect (CUD) is a fatty acid oxidation disorder (inherited metabolic disorder).
CUD is caused by mutations in the SLC22A5 gene, which provides instructions for a protein that moves carnitine into the cells. Carnitine is needed in the cell to convert certain fats to energy. People with CUD may have symptoms during times of high energy need such as when fasting or ill.