Charcot–Marie–Tooth disease misdiagnosed as chronic inflammatory demyelinating polyradiculoneuropathy: An international multicentric retrospective study

Background and purpose Charcot–Marie–Tooth (CMT) disease, an untreatable hereditary polyneuropathy, may mimic chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), a treatable neuropathy. Methods In this retrospective study, we analyzed the characteristics of CMT patients misdiagnosed as CIDP at 16 university hospitals in three countries, compared these patients with a reference group of CIDP patients, and estimated the cost of misdiagnosis. Results Among 1104 CIDP cases, we identified 35 CMT patients misdiagnosed as CIDP (3.2%). All were initially diagnosed with definite or probable CIDP (European Federation of Neurological Societies/Peripheral Nerve Society criteria), and mutations in PMP22, MPZ, and 10 other CMT genes were found in 34%, 31%, and 35% of cases, respectively. In comparison with a reference group of 35 CIDP patients, CMT patients were younger (median age at disease onset = 39 vs. 56 years) and more frequently had motor weakness at disease onset (80% vs. 29%), hearing loss (14% vs. 0%), normal brachial plexus imaging (70% vs. 40%), lower cerebrospinal fluid protein content (median = 0.5 vs. 0.8 g/L), and lower treatment response (20% vs. 69%). Treatment cost in these 35 misdiagnosed patients was estimated at 4.6 million euros (M€), whereas the cost of CMT genetic analysis in 1104 patients was estimated at 2.7 M€. Conclusions In this study, 35 of 1104 (3.2%) patients initially diagnosed with CIDP had CMT. Importantly, the cost of treating these 35 misdiagnosed patients was significantly higher than the cost of performing CMT genetic analysis in 1104 patients (4.6 M€ vs. 2.7 M€), suggesting that CMT genetic investigations should be more widely used before diagnosing CIDP. Amongst 1,104 CIDP cases, we identified 35 CMT patients misdiagnosed as CIDP (3.2%). In comparison with a reference group of 35 CIDP patients, CMT patients were younger, had more frequently motor weakness at disease onset, hearing loss, lower cerebrospinal fluid protein content, and lower treatment response. The cost of treating these 35 misdiagnosed patients was significantly higher than the cost of performing CMT genetic analysis in 1,104 patients (4.6 M€ vs 2.7 M€).