This retrospective medical chart review (RECENSUS) of approximately 100 XLMTM patients (with a goal to obtain 50 deceased and 20 living records) will provide further knowledge about the clinical manifestations and recorded medical management of XLMTM and potentially inform the design of future therapeutic intervention studies.

Inclusion Criteria:

• Patient diagnosed with XLMTM resulting from a confirmed mutation in the MTM1 gene, or a combination of XLMTM genetically confirmed family history and muscle biopsy
• Patient is male
• Access to available medical records for each patient
• Signed informed consent by the parent(s) or legal guardians and/or assent by the patient (when applicable), unless the associated IRB provides an appropriate consent waiver

Exclusion Criteria:

• Patient data after participation in an interventional study designed to treat XLMTM (patient data prior to participation in an interventional study may be included)

Males with X-linked myotubular myopathy