CPT2 and hyperinsulinemic hypoglycemia, familial, 4: Symptomatic CPT-II deficiency is usually caused by homozygous or compound heterozygous mutations in CPT2. The CPT2 p.R477W mutation found in the Nunavik Inuit is likely to lead to the loss of function as it is located in a highly conserved region where mutations known to cause CPT-II deficiency occur [28, 29].