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[Decreased C0 and other acylcarnitines]

Carnitine Uptake Defect (CUD)


Differential Diagnosis: Carnitine uptake defect (CUD). 

Condition Description: CUD is caused by a defect in the carnitine transporter that moves carnitine across the plasma membrane. Reduced carnitine limits acylcarnitine formation preventing transport of fatty acids into mitochondria, thereby limiting energy production. Tissues with high energy needs (skeletal and heart muscle) are particularly affected. 


  • Contact family to inform them of the newborn screening result and ascertain clinical status (poor feeding, lethargy, tachypnea)
  • Consult with pediatric metabolic specialist
  • Evaluate the newborn (tachycardia, hepatomegaly, reduced muscle tone); initiate emergency treatment as indicated by metabolic specialist
  • Initiate timely confirmatory/diagnostic testing recommended by specialist
  • Educate family about signs, symptoms and need for urgent treatment if infant becomes ill
  • Report findings to state newborn screening program (Carleigh Soule at 307-777-6297)  

Diagnostic Evaluation: Plasma and urine carnitine analysis will reveal decreased free and total carnitine (C0) in plasma and over excretion of carnitine in urine. The newborn’s mother should be investigated as well because several cases of maternal CUD have been identified following an abnormal screening result in their offspring. Transporter assays and OCTN2 gene sequencing establish diagnosis. 

Clinical Considerations: Carnitine transporter defect has a variable expression and variable age of onset. Characteristics manifestitations include lethargy, hypotonia, hepatomegaly, and cardia decomposition due to cardiomyopathy. Hypoglycemia is typical in acute episodes. 

Additional Information: (Click on the name to take you to the website) 

Genetic Home Reference                                    Wyoming Department of Health                                

New England Consortium                                     Colorado Newborn Screening                   

Online Mendelian Inheritance in Man                       American Academy of Pediatrics                     


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