Molecular Epidemiology of Charcot-Marie-Tooth Disease in Northern Ostrobothnia, Finland: A Population-Based Study

Background: Charcot-Marie-Tooth (CMT) disease is the most common hereditary neuromuscular disorder with a population prevalence of 9.7-82.3/100,000. In this study, we have estimated the prevalence of CMT and its subtypes in Finland and examined the frequency of molecular etiologies. Methods: A population-based survey included adult patients with peripheral neuropathy from the province of Northern Ostrobothnia, Finland. Secondary causes of peripheral polyneuropathy were excluded and patients with clinical and neurophysiological features pertinent with CMT were included. Molecular diagnostics was carried out when DNA was available. Results: We found 107 subjects with CMT yielding a prevalence 34.6/100,000 in Northern Ostrobothnia. The heterozygous point mutation p.His123Arg in ganglioside induced differentiation associated protein 1 (GDAP1) was found in 31.5% and peripheral myelin protein 22 (PMP22) duplication in 16.9% of the affected. Point mutations in myelin protein zero, mitofusin 2, and gap junction protein beta 1 accounted for 6.7% of the cases. In addition, 18 persons had hereditary neuropathy with liability to pressure palsies and 15 of them carried the PMP22 deletion. Conclusions: The prevalence of CMT in Northern Ostrobothnia, Finland, seems to be slightly higher than those in previous studies in European populations. Founder mutation in the GDAP1 gene accounts for a large part of the genetically defined CMT2 in Finland.