Centronuclear myopathy
| Centronuclear myopathy | |
|---|---|
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| Muscle biopsy from the quadriceps taken at 3 months of age from a girl with X-linked centronuclear ("myotubular") myopathy due to a mutation in the myotubularin (MTM1) gene and extremely skewed X-inactivation (H&E stain, transverse section). Note marked variability in fibre size, moderate increase in connective tissue and numerous central nuclei. | |
| Classification and external resources | |
| Specialty | neurology |
| ICD-10 | G71.2 |
| ICD-9-CM | 359.0 |
| OMIM | 160150 310400 255200 |
| DiseasesDB | 31983 |
| eMedicine | neuro/76 |
| MeSH | D020914 |
| GeneReviews | |
Centronuclear myopathies (CNM) are a group of congenital myopathies where cell nuclei are abnormally located in skeletal muscle cells. In CNM the nuclei are located at a position in the center of the cell, instead of their normal location at the periphery.
Symptoms of CNM include severe hypotonia, hypoxia-requiring breathing assistance, and scaphocephaly. Among centronuclear myopathies, the X-linked myotubular myopathy form typically presents at birth, and is thus considered a congenital myopathy. However, some centronuclear myopathies may present later in life.
As with other myopathies, the clinical manifestations of MTM/CNM are most notably muscle weakness and associated disabilities. Congenital forms often present with neonatal low muscle tone, severe weakness, delayed developmental milestones (particularly gross motor milestones such as head control, crawling, and walking) and pulmonary complications (presumably due to weakness of the muscles responsible for respiration). While some patients with centronuclear myopathies remain ambulatory throughout their adult life, others may never crawl or walk and may require wheelchair use for mobility. There is substantial variability in the degree of functional impairment among the various centronuclear myopathies. Although this condition only affects the voluntary muscles, several children have suffered from cardiac arrest, possibly due to the additional stress placed on the heart.
Other observed features have been high arched palate, long digits, bell shaped chest and long face.
Myotubular myopathy only affects muscles and does not impact intelligence in any shape or form.
X-linked myotubular myopathy was traditionally a fatal condition of infancy, with life expectancy of usually less than two years. There appears to be substantial variability in the clinical severity for different genetic abnormalities at that same MTM1 gene. Further, published cases show significant differences in clinical severity among relatives with the same genetic abnormality at the MTM1 gene. Most truncating mutations of MTM1 cause a severe and early lethal phenotype, while some missense mutations are associated with milder forms and prolonged survival (up to 54 years).
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