Myotubular Myopathy; X-Linked Centronuclear Myopathy; Centronuclear Myopathy; Classic X-Linked Myotubular Myopathy

X-Linked Myotubular Myopathy (XLMTM) is a condition that primarily affects muscles used for movement (skeletal muscles) and occurs almost exclusively in males. Individuals with this condition have muscle weakness (myopathy) and decreased muscle tone (hypotonia) that is usually evident at birth. These muscle problems impair the development of motor skills such as sitting, standing, and walking. Affected infants may also have difficulties with feeding due to muscle weakness. Individuals with X-linked myotubular myopathy frequently lack the muscle strength for unassisted breathing and must be supported with a mechanical ventilator. Some individuals need full-time breathing assistance, while some require only periodic assisted ventilation, typically during sleep. Affected individuals may also have weakness in the muscles that control eye movement and other muscles of the face, absent reflexes, and musculoskeletal deformities or contractures.

Because of their severe breathing problems, individuals with XLMTM usually survive only into early childhood; however, some people with this condition live into adulthood.

Diagnostic testing: Once clinical manifestations have occurred, the diagnosis is established by a combination of clinical examination, muscle biopsy, and genetic testing.

Physical findings: The physical findings of XLMTM may include:

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  Hypotonia;

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  Difficulties with feeding due to muscle weakness;

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  Weakness in the eye muscles that control eye movement (ophthalmoplegia);

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  Absent reflexes (areflexia);

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  An abnormal curvature of the spine (scoliosis);

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  Joint contractures of the hips and knees; and

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  A large head with a narrow and elongated face.

ICD-9: 359.0

ICD-10: G71.2

XLMTM presents at birth with weakness, hypotonia, and respiratory distress. Because of their severe breathing problems, individuals with severe XLMTM usually have a high incidence of death from respiratory failure in infancy or early childhood. Most males will fail to reach milestones and will not gain ambulation.

Treatment is supportive and symptomatic. Tracheostomy, G-tube feeding, and assistive communication devices are often required. Medical subspecialists should address specific medical complications (for example, scoliosis).

SUGGESTED PROGRAMMATIC ASSESSMENT*

REMARKS

Listing level musculoskeletal findings must be documented; diagnosis of XLMTM or lab testing results alone does not meet listing severity.