What is the mortality and morbidity associated with carnitine deficiency?

Updated: Dec 13, 2019
  • Author: Fernando Scaglia, MD, FACMG; Chief Editor: Maria Descartes, MD  more...
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In order to abate the mortality and morbidity of undiagnosed primary carnitine deficiency, this condition has been included in the expanded newborn screening program in several states within the United States. [4] Primary carnitine deficiency can be identified in infants by expanded newborn screening using tandem mass spectrometry. [5] Low levels of free carnitine (C0) are detected. However, low carnitine levels in newborns may also reflect maternal primary carnitine deficiency.

Sudden death: Unfortunately, the first clinical manifestation in asymptomatic individuals with primary carnitine deficiency may be sudden death. This also may occur in patients with secondary carnitine deficiency as a consequence of ventricular tachycardia or fibrillation. [6]

Heart failure: Patients with primary carnitine deficiency develop a progressive cardiomyopathy that usually presents at a later age. The cardiac function does not respond to inotropes or diuretics. If the condition is not correctly diagnosed and no carnitine is supplemented, progressive heart failure eventually leads to death. Heart failure caused by dilated cardiomyopathy may be the presenting syndrome in patients with secondary carnitine deficiency caused by defects in beta-oxidation, such as long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) and very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency.

Hypoglycemic hypoketotic encephalopathy: Acute encephalopathy accompanied by hypoketotic hypoglycemic episodes usually presents in younger infants with primary carnitine deficiency. Periods of fasting in association with viral illness trigger these acute episodes. Some patients have developmental delay and CNS dysfunction associated with these episodes. If no carnitine replacement is given, recurrent episodes of encephalopathy may ensue.

A significant cohort of patients with primary carnitine deficiency do not present in infancy or early childhood as previously thought but remain asymptomatic into adulthood. These observations are derived from the experience of expanded newborn screening programs that identified maternal primary carnitine deficiency in mothers who were for the most part minimally symptomatic or asymptomatic. One mother with primary carnitine deficiency was reported to have a history of syncope that worsened during pregnancy, when plasma carnitine levels are physiologically lower. [7]

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