Carnitine-acylcarnitine translocase deficiency

Roser Pons MD (Dr. Pons of the University of Athens in Greece has no relevant financial relationships to disclose.)
Tyler Reimschisel MD, editor. (Dr. Reimschisel of Vanderbilt University has received contracted research grants from Shire.)
Originally released November 28, 1994; last updated November 27, 2017; expires November 27, 2020

This article includes discussion of carnitine-acylcarnitine translocase deficiency, CACT deficiency, translocase deficiency, fatty acid oxidation defect, and inborn error of energy metabolism. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.


Carnitine-acylcarnitine translocase deficiency is a rare inborn error of energy metabolism involving the carnitine cycle. This enzyme deficiency is considered the most severe disorder of fatty acid oxidation. Its clinical features are related to the impairment of fasting adaptation and cardiac and skeletal muscle metabolism, and its presentation overlaps with the clinical presentation of the severe neonatal form of carnitine palmitoyltransferase type-2 deficiency. In this article, the author describes the developments of this disorder including the expanding clinical phenotype, the management, and the advances in the understanding of the genetics of this condition since the human gene was cloned in 1997.

Key points


• Carnitine-acylcarnitine translocase deficiency shares clinical features with other defects of long-chain fatty acid oxidation.


• The biochemical findings may be indistinguishable from the neonatal form of carnitine palmitoyltransferase type-2 deficiency.


• The mortality rate is high and it occurs mainly in the first year of life.


• In at least a quarter of cases, patients show a mild presentation with long-term survival.


• Treatment consists of low-fat/high-carbohydrate diet with frequent meals and avoidance of fasting.

Historical note and terminology

Carnitine-acylcarnitine translocase deficiency was 1 of the latest inborn errors of mitochondrial fatty acid oxidation to be discovered (Stanley et al 1992). Approximately a dozen defects in the pathway are known and 4 of them involve the carnitine cycle. These disorders all share similar clinical features related to their impairment of fasting adaptation, cardiac metabolism, and skeletal muscle metabolism (Tein 2013).

Since the first report of carnitine-acylcarnitine translocase deficiency by Stanley and colleagues in 1992, approximately 57 additional cases have been reported (Lopriore et al 2001; Iacobazzi et al 2004; Wang et al 2011; Vitoria et al 2015; Yan et al 2017). The majority of patients become symptomatic in the newborn period. The mortality rate reaches up to 65% of patients in the first year of life due to cardiac complications (Mahapatra et al 2017). Several patients have been described with a milder phenotype and long-term survival (Lopriore et al 2001; Iacobazzi et al 2004; Rubio-Gozalbo et al 2004; Vitoria et al 2015).

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