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Systemic Primary Carnitine Deficiency.


El-Hattab AW.


GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2015.
2012 Mar 15 [updated 2014 Jun 26].



Systemic primary carnitine deficiency (CDSP) is a disorder of the carnitine cycle that results in defective fatty acid oxidation. It encompasses a broad clinical spectrum including: Metabolic decompensation in infancy typically presenting between age three months and two years with episodes of hypoketotic hypoglycemia, poor feeding, irritability, lethargy, hepatomegaly, elevated liver transaminases, and hyperammonemia triggered by fasting or common illnesses such as upper respiratory tract infection or gastroenteritis; Childhood myopathy involving heart and skeletal muscle with onset between age two and four years; Fatigability in adulthood; or Absence of symptoms. The latter two categories often include mothers diagnosed with CDSP after newborn screening has identified low carnitine levels in their infants.


Plasma carnitine levels are extremely reduced in CDSP. The diagnosis is confirmed by the demonstration of reduced fibroblast carnitine transport or biallelic pathogenic variants in SLC22A5.


Treatment of manifestations: Metabolic decompensation and skeletal and cardiac muscle functions improve with 100-400 mg/kg/day oral levocarnitine (L-carnitine) if it is started before irreversible organ damage occurs. Hypoglycemic episodes are treated with intravenous dextrose infusion; cardiomyopathy requires management by specialists in cardiology. Prevention of primary manifestations: The manifestations of CDSP can be prevented by use of oral L-carnitine supplementation to maintain normal plasma carnitine concentrations. Surveillance: Suggested: Echocardiogram and electrocardiogram: annually during childhood and less frequently in adulthood; Plasma carnitine concentration: monitor frequently until levels reach the normal range, then, measure three times a year during infancy and early childhood, twice a year in older children, and annually in adults; Serum creatine kinase concentration and liver transaminases: consider measuring during acute illnesses. Agents/circumstances to avoid: Fasting longer than age-appropriate periods. Evaluation of relatives at risk: Measure plasma carnitine levels in sibs of an affected individual. Pregnancy management: Pregnant women with CDSP require close monitoring of plasma carnitine levels and increased carnitine supplementation as needed to maintain normal plasma carnitine levels.


CDSP is inherited in an autosomal recessive manner. At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Carrier testing for at-risk family members and prenatal diagnosis for pregnancies at increased risk are possible if the SLC22A5 pathogenic variants in the family are known.

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