Identification of Four Novel Mutations in Patients with Carnitine Palmitoyltransferase II (CPT II) Deficiency

Carnitine palmitoyltransferase II (CPT II) deficiency, an autosomal recessive disorder of fatty-acid oxidation, presents as three distinct phenotypes (neonatal, infantile, and adult onset). In order to investigate the molecular basis of these three phenotypes, six patients with CPT II deficiency have been studied. All six unrelated patients in this study experienced the clinical symptoms of CPT II deficiency. Three patients had the neonatal form, one had the milder infantile form, and the remaining two had the adult-onset form with “muscular” symptoms only. Their diagnoses were based uponin vitroanalysis of the mitochondrial β-oxidation pathway in fibroblasts and standard enzyme assays. We devised a method to screen the entire coding sequence and flanking splice junction of the CPT II gene. A total of six different mutations have been identified, including four novel mutations. Among them, the previously reported common mutation, S113L, was only found in 3 of 12 variant alleles. Three of the six mutations have been identified in a few unrelated patients, while the remaining three have been found in single families. This study, as well as those by others, indicates genetic heterogeneity in this disease. In addition to tabulating the mutations, the correlation of mutant genotype to clinical phenotype is briefly discussed.