A natural history study of X-linked myotubular myopathy
Kimberly Amburgey, Etsuko Tsuchiya, Sabine de Chastonay, Michael Glueck, Rachel Alverez, Cam-Tu Nguyen, Anne Rutkowski, Joseph Hornyak, Alan H Beggs, James J Dowling, Kimberly Amburgey, Etsuko Tsuchiya, Sabine de Chastonay, Michael Glueck, Rachel Alverez, Cam-Tu Nguyen, Anne Rutkowski, Joseph Hornyak, Alan H Beggs, James J Dowling
Abstract
Objective: To define the natural history of X-linked myotubular myopathy (MTM).
Methods: We performed a cross-sectional study that included an online survey (n = 35) and a prospective, 1-year longitudinal investigation using a phone survey (n = 33).
Results: We ascertained data from 50 male patients with MTM and performed longitudinal assessments on 33 affected individuals. Consistent with existing knowledge, we found that MTM is a disorder associated with extensive morbidities, including wheelchair (86.7% nonambulant) and ventilator (75% requiring >16 hours of support) dependence. However, unlike previous reports and despite the high burden of disease, mortality was lower than anticipated (approximate rate 10%/y). Seventy-six percent of patients with MTM enrolled (mean age 10 years 11 months) were alive at the end of the study. Nearly all deaths in the study were associated with respiratory failure. In addition, the disease course was more stable than expected, with few adverse events reported during the prospective survey. Few non-muscle-related morbidities were identified, although an unexpectedly high incidence of learning disability (43%) was noted. Conversely, MTM was associated with substantial burdens on patient and caregiver daily living, reflected by missed days of school and lost workdays.
Conclusions: MTM is one of the most severe neuromuscular disorders, with affected individuals requiring extensive mechanical interventions for survival. However, among study participants, the disease course was more stable than predicted, with more individuals surviving infancy and early childhood. These data reflect the disease burden of MTM but offer hope in terms of future therapeutic intervention.
Copyright © 2017 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.
Figures
References
- Laporte J, Hu LJ, Kretz C, et al. . A gene mutated in X-linked myotubular myopathy defines a new putative tyrosine phosphatase family conserved in yeast. Nat Genet 1996;13:175–182.
- Das S, Dowling J, Pierson CR. X-linked centronuclear myopathy. In: Pagon RA, Adam MP, Bird TD, et al., editors. GeneReviews. Seattle, WA: University of Washington; 1993–2017.
- Childers MK, Joubert R, Poulard K, et al. . Gene therapy prolongs survival and restores function in murine and canine models of myotubular myopathy. Sci Transl Med 2014;6:220ra210.
- Lawlor MW, Armstrong D, Viola MG, et al. . Enzyme replacement therapy rescues weakness and improves muscle pathology in mice with X-linked myotubular myopathy. Hum Mol Genet 2013;22:1525–1538.
- Cowling BS, Chevremont T, Prokic I, et al. . Reducing dynamin 2 expression rescues X-linked centronuclear myopathy. J Clin Invest 2014;124:1350–1363.
- Sabha N, Volpatti JR, Gonorazky H, et al. . PIK3C2B inhibition improves function and prolongs survival in myotubular myopathy animal models. J Clin Invest 2016;126:3613–3625.
- McEntagart M, Parsons G, Buj-Bello A, et al. . Genotype-phenotype correlations in X-linked myotubular myopathy. Neuromuscul Disord 2002;12:939–946.
- Herman GE, Finegold M, Zhao W, de Gouyon B, Metzenberg A. Medical complications in long-term survivors with X-linked myotubular myopathy. J Pediatr 1999;134:206–214.
- Abath Neto O, Silva MR, Martins Cde A, et al. . A study of a cohort of X-linked myotubular myopathy at the clinical, histologic, and genetic levels. Pediatr Neurol 2016;58:107–112.
- Lee EH, Yum MS, Park SJ, et al. . Two cases of X-linked myotubular myopathy with novel MTM1 mutations. J Clin Neurol 2013;9:57–60.
- Colombo I, Scoto M, Manzur AY, et al. . Congenital myopathies: natural history of a large pediatric cohort. Neurology 2015;84:28–35.
- Wang CH, Dowling JJ, North K, et al. . Consensus statement on standard of care for congenital myopathies. J Child Neurol 2012;27:363–382.
- Main M, Kairon H, Mercuri E, Muntoni F. The Hammersmith Functional Motor Scale for children with spinal muscular atrophy: a scale to test ability and monitor progress in children with limited ambulation. Eur J Paediatr Neurol 2003;7:155–159.
- Pierson CR, Dulin-Smith AN, Durban AN, et al. . Modeling the human MTM1 p.R69C mutation in murine Mtm1 results in exon 4 skipping and a less severe myotubular myopathy phenotype. Hum Mol Genet 2012;21:811–825.
- Laporte J, Blondeau F, Gansmuller A, Lutz Y, Vonesch JL, Mandel JL. The PtdIns3P phosphatase myotubularin is a cytoplasmic protein that also localizes to Rac1-inducible plasma membrane ruffles. J Cell Sci 2002;115:3105–3117.
- Fattori F, Maggi L, Bruno C, et al. . Centronuclear myopathies: genotype-phenotype correlation and frequency of defined genetic forms in an Italian cohort. J Neurol 2015;262:1728–1740.
Source: PubMed