Saturday, August 12, 2017

A CMT potpourri

Cornett KM, Menezes MP, Shy RR, Moroni I, Pagliano E, Pareyson D, Estilow T, Yum SW, Bhandari T, Muntoni F, Laura M, Reilly MM, Finkel RS, Eichinger KJ, Herrmann DN, Bray P, Halaki M, Shy ME, Burns J; CMTPedS Study Group. Natural history of Charcot-Marie-Tooth disease during childhood. Ann Neurol. 2017 Aug 10. doi: 10.1002/ana.25009. [Epub ahead of print]

To determine the rate of disease progression in a longitudinal natural history study of children with Charcot-Marie-Tooth disease (CMT).
206 (103 female) participants aged 3-20 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%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), nine participants with CMT1B/MPZ mutation progressed by 2.2±5.1 (11% change), six participants with CMT2A/MFN2 mutation progressed by 6.2±7.9 (23% change), and seven 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) while 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.

Cornett KM, Menezes MP, Bray P, Halaki M, Shy RR, Yum SW, Estilow T, Moroni I, Foscan M, Pagliano E, Pareyson D, Laurá M, Bhandari T, Muntoni F, Reilly MM, Finkel RS, Sowden J, Eichinger KJ, Herrmann DN, Shy ME, Burns J; Inherited Neuropathies Consortium. Phenotypic Variability of Childhood Charcot-Marie-Tooth  Disease. JAMA Neurol. 2016 Jun 1;73(6):645-51. 

Disease severity of childhood Charcot-Marie-Tooth disease (CMT) has not been extensively characterized, either within or between types of CMT to date.
To assess the variability of disease severity in a large cohort of children and adolescents with CMT.
A cross-sectional study was conducted among 520 children and adolescents aged 3 to 20 years at 8 universities and hospitals involved in the Inherited Neuropathies Consortium between August 6, 2009, and July 31, 2014, in Australia, Italy, the United Kingdom, and the United States. Data analysis was conducted from August 1, 2014, to December 1, 2015.
Scores on the Charcot-Marie-Tooth Disease Pediatric Scale (CMTPedS), a well-validated unidimensional clinical outcome measure to assess disease severity. This instrument includes 11 items assessing fine and gross motor function, sensation, and balance to produce a total score ranging from 0 (unaffected) to 44 (severely affected).
Among the 520 participants (274 males) aged 3 to 20 years, CMT type 1A (CMT1A) was the most prevalent type (252 [48.5%]), followed by CMT2A (31 [6.0%]), CMT1B (15 [2.9%]), CMT4C (13 [2.5%]), and CMTX1 (10 [1.9%]). Disease severity ranged from 1 to 44 points on the CMTPedS (mean [SD], 21.5 [8.9]), with ankle dorsiflexion strength and functional hand dexterity test being most affected. Participants with CMT1B (mean [SD] CMTPedS score, 24.0 [7.4]), CMT2A (29.7 [7.1]), and CMT4C (29.8 [8.6]) were more severely affected than those with CMT1A (18.9 [7.7]) and CMTX1 (males: 15.3 [7.7]; females: 13.0 [3.6]) (P < .05). Scores on the CMTPedS tended to worsen principally during childhood (ages, 3-10 years) for participants with CMT4C and CMTX1 and predominantly during adolescence for those with CMT1B and CMT2A (ages, 11-20 years), while CMT1A worsened consistently throughout childhood and adolescence. For individual items, participants with CMT4C recorded more affected functional dexterity test scores than did those with all other types of CMT (P < .05). Participants with CMT1A and CMTX1 performed significantly better on the 9-hole peg test and balance test than did those with all other types of CMT (P < .05). Participants with CMT2A had the weakest grip strength (P < .05), while those with CMT2A and CMT4C exhibited the weakest ankle plantarflexion and dorsiflexion strength, as well as the lowest long jump and 6-minute walk test distances (P < .05). Multiple regression modeling identified increasing age (r = 0.356, β = 0.617, P < .001) height (r = 0.251, β = 0.309, P = .002), self-reported foot pain (r = 0.162, β = .114, P = .009), and self-reported hand weakness (r = 0.243, β = 0.203, P < .001) as independent predictors of disease severity.
These results highlight the phenotypic variability within CMT genotypes and mutation-specific manifestations between types. This study has identified distinct functional limitations and self-reported impairments to target in future therapeutic trials.

Panosyan FB, Laura M, Rossor AM, Pisciotta C, Piscosquito G, Burns J, Li J, Yum SW, Lewis RA, Day J, Horvath R, Herrmann DN, Shy ME, Pareyson D, Reilly MM, Scherer SS; Inherited Neuropathies Consortium—Rare Diseases Clinical Research Network (INC-RDCRN). Cross-sectional analysis of a large cohort with X-linked Charcot-Marie-Tooth disease (CMTX1). Neurology. 2017 Aug 2. pii:10.1212/WNL.0000000000004296. doi: 10.1212/WNL.0000000000004296. [Epub ahead of  print]

To extend the phenotypic description of Charcot-Marie-Tooth disease (CMTX1) and to draw new genotype-phenotype relationships.
Mutations in GJB1 cause the main X-linked form of CMTX (CMTX1). We report cross-sectional data from 160 patients (from 120 different families, with 89 different mutations) seen at the Inherited Neuropathies Consortium centers.
We evaluated 87 males who had a mean age of 41 years (range 10-78 years) and 73 females who had a mean age of 46 years (range 15-84 years). Sensory-motor polyneuropathy affects both sexes, more severely in males than in females, and there was a strong correlation between age and disease burden in males but not in females. Compared with females, males had more severe reduction in motor and sensory neurophysiology parameters. In contrast to females, the radial nerve sensory response in older males tended to be more severely affected compared with younger males. Median and ulnar nerve motor amplitudes were also more severely affected in older males, whereas ulnar nerve motor potentials tended to be more affected in older females. Conversely, there were no statistical differences between the sexes in other features of the disease, such as problems with balance and hand dexterity.

In the absence of a phenotypic correlation with specific GJB1 mutations, sex-specific distinctions and clinically relevant attributes need to be incorporated into the measurements for clinical trials in people with CMTX1.

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