Genetic epidemiology, demographic, and clinical characteristics of Charcot-Marie-tooth disease in the island of Gran Canaria (Spain).

Charcot-Marie-Tooth (CMT) disease is the most common hereditary neuromuscular disorder. This study involves the entire known CMT patient registry in Gran Canaria, represented by 256 patients belonging to 79 unrelated families, who were clinically and genetically characterized, along with physical and neurophysiological evaluation on 181 and 165 patients, respectively. Complete genotyping showed an estimated prevalence of CMT disease of 30.08/100 000 (95% confidence interval [CI] = 26.5;33.9), corresponding mainly (78.5%) to CMT1A (23.6/100 000) and hereditary neuropathy with liability to pressure palsies [HNPP] 17.5%; 5.29/100 000). Most patients (198) with CMT1A carried the 17p11.2 duplication including the PMP22 gene, 45 patients with HNPP were all affected by deletion of the 17p11.2 locus, and 10 patients presented with axonal phenotypes: CMT2A (MFN2), CMT2N (AARS), and CMT1X (GJB1). Despite showing a classical CMT1A phenotype, we found a much earlier age of onset in our CMT1A patients, along with increased frequency of appearance of postural hand tremor. Bilateral tongue atrophy was an additional phenotype observed. Being this CMT1A group, one of the largest cohorts known to date, this study provided a unique opportunity to further define the clinical phenotype of CMT1A patients carrying the 17p11.2 duplication in a homogeneous ethnic group.