A Medical Chart Review of Patients With X-Linked Myotubular Myopathy (XLMTM)

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)