Identification of the infant-type R631C mutation in patients with the benign muscular form of CPT2 deficiency

Carnitine palmitoyltransferase 2 (CPT2) deficiency is the most common defect of mitochondrial fatty acid oxidation; three different clinical phenotypes have been described but the adult form, involving exclusively the skeletal muscle, is the most frequent. We describe herein 3 families where 4 individuals manifested with the adult form of CPT2 deficiency. CPT2 gene molecular analysis identified the homozygous R631C mutation, so far only reported in severe infantile cases. Our data evidenced that R631C mutation is not exclusively detected in the infantile form but it may be present in a wider spectrum of CPT2 phenotypes. These findings indirectly suggest that other modulators may influence clinical severity of CPT2 deficiency.