Some research suggests that this theory may be acceptable for infant-onset myotubular myopathy (mutations at the MTM1 gene on the X chromosome) but may not be acceptable for the autosomal forms of centronuclear myopathy, while other research suggests that the growth arrest mechanism may be responsible for all forms of MTM and CNM. Regardless of whether the myopathy is caused by arrest at the "myotubular" stage, for historical reasons the name myotubular myopathy persists and is widely accepted.As a reference to the term myotubular myopathy (MTM), when a genetic abnormality on the X chromosome was determined to be involved in a substantial percentage of individuals with the myotubular/centronuclear appearance on muscle biopsy, researchers named the gene segment MTM1. Similarly, the protein typically produced by that gene is called "myotubularin". Advocacy
There are several global advocacy groups working closely to educate newly affected families on care guidelines. The Joshua Frase Foundation is a comprehensive resource for care guidelines for Centronuclear myopathies. In the United States, children with congenital myopathies often receive therapy services through Early Intervention Programs (EIP, providing services from birth to 3 years old) administered by the state of residence. After the child is 3 years old, Special Education services are provided under the federal Individuals with Disabilities Education Act (IDEA, with myopathies being eligible when classified under conditions causing muscular weakness).
Centronuclear myopathies (CNM) are a group of congenital myopathies where cell nuclei are abnormally located in the center of muscle cells 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. Presentation
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). Involvement of the facial muscles may cause ophthalmoplegia or ptosis. A mutation in the RYR1 gene causing CNM may also cause susceptibility to malignant hyperthermia, a potentially life-threatening reaction to anesthesia. 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 had 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.