Natural History and Genotype-Phenotype Correlations in Mitochondrial Leukoencephalopathies

Inclusion Criteria: * Confirmed diagnosis of ML, confirmed by: * Neuroradiological evidence of a MRI pattern of white matter alterations compatible with leukoencephalopathy * Genetic evidence of pathogenic variants in nuclear or mitochondrial genes * Availability of clinical data, including medical records detailing symptom onset, disease progression, neuroimaging findings, and clinical management. * Written informed consent obtained from the patient or their legal guardian (for minors or individuals with cognitive impairment). If the patient is deceased, consent for the use of medical records in this study will be obtained from the legally authorized representative or next of kin Exclusion Criteria: * Unconfirmed diagnosis of mitochondrial leukoencephalopathy , including cases where: * MRI findings do not demonstrate a white matter alteration pattern compatible with leukoencephalopathy * There is neither genetic confirmation of a pathogenic variant in nuclear or mitochondrial genes * Insufficient clinical data, including cases where medical records lack essential information on symptom onset, disease progression, neuroimaging findings, or clinical management, preventing a meaningful contribution to the study's objectives. * Concomitant diagnosis of another genetic disorder that may independently contribute to white matter abnormalities or neurological symptoms, confounding the assessment of ML progression and clinical outcomes * Unavailability of written informed consent