Systemic primary carnitine deficiency

Systemic primary carnitine deficiency is an inborn error of fatty acid transport. A defect in the OCTN2 transporter, encoded by the SLC22A5 gene on chromosome 5, stops carnitine from crossing the cell membrane into tissues, so fatty acid oxidation is impaired. The result can be chronic muscle weakness, cardiomyopathy, low blood sugar and liver dysfunction. It is inherited in an autosomal recessive manner, with a mutated allele from each parent. Acute episodes are often preceded by metabolic stress such as prolonged fasting, infection or vomiting, while cardiomyopathy can develop without one and can be fatal. Where expanded newborn screening exists the condition can be found soon after birth, and lifelong high-dose carnitine supplementation is an effective treatment that must be rigorously maintained.