[citation needed] This condition is caused by mutations in the myotubularin (MTM1) gene which is located on the long arm of the X chromosome (Xq28).

Two exceptions for a female with a X-linked recessive abnormality to have clinical symptoms: one is a manifesting carrier and the other is X-inactivation.

A manifesting carrier usually has no noticeable problems at birth; symptoms show up later in life.

Girls with myopathy and a muscle biopsy showing a centronuclear pattern should be tested for MTM1 mutations.

[1] Abbreviations XL-MTM, XLMTM or X-MTM are sometimes used to emphasize that the mutation occurs on the X chromosome.