Natural history of Charcot-Marie-Tooth disease during childhood

To determine the rate of disease progression in a longitudinal natural history study of children with Charcot-Marie-Tooth (CMT) disease.

Two hundred six (103 female) participants aged 3 to 20 years enrolled in the Inherited Neuropathies Consortium were assessed at baseline and 2 years. Demographic, anthropometric, and diagnostic information were collected. Disease progression was assessed with the CMT Pediatric Scale (CMTPedS), a reliable Rasch-built linearly weighted disability scale evaluating fine and gross motor function, strength, sensation, and balance.

On average, CMTPedS Total scores progressed at a rate of 2.4 ± 4.9 over 2 years (14% change from baseline; p < 0.001). There was no difference between males and females (mean difference, 0.5; 95% confidence interval [CI], -0.9 to 1.9; p = 0.49). The most responsive CMTPedS items were dorsiflexion strength (z-score change, -0.3; 95% CI, -0.6 to -0.05; p = 0.02), balance (z-score change, -1.0; 95% CI, -1.9 to -0.09; p = 0.03), and long jump (z-score change, -0.4; 95% CI, -0.7 to -0.02; p = 0.04). Of the most common genetic subtypes, 111 participants with CMT1A/PMP22 duplication progressed by 1.8 ± 4.2 (12% change from baseline; p < 0.001), 9 participants with CMT1B/MPZ mutation progressed by 2.2 ± 5.1 (11% change), 6 participants with CMT2A/MFN2 mutation progressed by 6.2 ± 7.9 (23% change), and 7 participants with CMT4C/SH3TC2 mutations progressed by 3.0 ± 4.5 (12% change). Participants with CMT2A progressed faster than CMT1A (mean difference, -4.4; 95% CI, -8.1 to -0.8; p = 0.02). Children with CMT1A progressed consistently through early childhood (3-10 years) and adolescence (11-20 years; mean difference, 1.1; 95% CI, -0.6 to 2.7; p = 0.19), whereas CMT2A appeared to progress faster during early childhood than adolescence (mean difference, 10.0; 95% CI, -2.2 to 22.2; p = 0.08).

Using the CMTPedS as an outcome measure of disease severity, children with CMT progress at a significant rate over 2 years. Understanding the rate at which children with CMT deteriorate is essential for adequately powering trials of disease-modifying interventions. Ann Neurol 2017;82:353-359.