Prospective, Longitudinal Study of the Natural History and Functional Status of Patients With Myotubular Myopathy (MTM)

This is a prospective, non-interventional, longitudinal study of the natural history and
function of patients with MTM. The study duration is 36 months. The enrollment period will be
12 months and each patient will be assessed over 24 months. Data will be analyzed at baseline
and annually thereafter and reports will be prepared based on these analyses. A final report
will summarize findings after all patients have completed 24 months of follow-up. Assessments
performed in this study will be based on the age and ambulatory status of the patient. The
assessments will also be adjusted to account for the variability in both phenotypes and age
of the patients who may participate in this study. Patients will be evaluated at Baseline,
Month 6, Month 12 and Month 24. It is anticipated that approximately 60 patients from the
United States, Canada and Europe will be included in this study.

Inclusion criteria:

- Patients of any age (newborns included) may participate.

- Patients over 18 years of age and parent(s)/legal guardian(s) of patients <18 years of
age must provide written informed consent prior to participating in the study and
informed assent will be obtained from minors at least 7 years of age when required by
regulation.

- MTM resulting from a mutation in the MTM1 gene.

- Male or symptomatic female. A symptomatic female will be defined by the motor function
assessment by Motor Function Measure (MFM) or North Star Ambulatory Assessment (NSAA)
below 80% of the total score.

- Willing and able to comply with all protocol requirements and procedures.

Exclusion criteria:

- Other disease which may significantly interfere with the assessment of MTM and is
clearly not related to the disease.

- Currently enrolled in a treatment study; or treatment with an experimental therapy
other than pyridostigmine.