l-Carnitine deficiency leads to an accumulation of free fatty acids in the cell cytoplasm and of acyl-coenzyme A (CoA) in the mitochondria. This produces a toxic effect and disturbs fatty acid use for energy production (Kletzmayr et al 1999). Deficiency symptoms (Kelly 1998) include the following:
• progressive myasthenia
• congestive heart failure
• neuromuscular disorders
• failure to thrive in infants
• muscle fatigue and cramps
• myoglobinaemia following exercise.
Elevation of triglycerides may also occur due to the role of carnitine in fatty acid metabolism. PRIMARY DEFICIENCY
People at risk of primary deficiency are vegetarians, preterm infants and infants receiving a carnitine-free formula, and those with an inherited functional defect.
Clinical note— Primary carnitine deficiency: an uncommon inherited disorder
Primary carnitine deficiency is an uncommon inherited disorder, related to a functional defect in plasma membrane carnitine transport in muscle and the kidneys. These conditions have been classified as either systemic or myopathic (Evangeliou & Vlassopoulos 2003, Matera et al 2003). Systemic carnitine deficiency is reflected by low levels of carnitine in plasma and muscle and may result in cardiomyopathy, skeletal myopathy, hypoglycaemia and hyperammonaemia (Hendler & Rorvik 2001). Myopathic deficiency presents with normal plasma but low muscle carnitine levels and is a defect of carnitine transport across the muscle cell membrane (Winter et al 1987)._
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