This will be a single-center, single-arm, non-interventional natural history study to evaluate the longitudinal clinical course, functional outcome measures, and candidate biomarkers for individuals with DNA repair disorders, including Cockayne syndrome (CS), xeroderma pigmentosum (XP), and trichothiodystrophy (TTD).

This will be a single-center, single-arm, non-interventional natural history study to evaluate the longitudinal clinical course, functional outcome measures, and candidate biomarkers for individuals with DNA repair disorders, including Cockayne syndrome (CS), xeroderma pigmentosum (XP), and trichothiodystrophy (TTD). Our hypothesis is that a reliable and reproducible baseline natural history course can be established for DNA repair disorders using the Early Childhood Assessment of Balance (ECAB) as a primary endpoint and other measures as secondary and exploratory endpoints that may be used in future therapeutic clinical trials.

Inclusion Criteria:

• Diagnosis of Cockayne syndrome (CS), xeroderma pigmentosum (XP), or trichothiodystrophy (TTD), based on genetic testing and/or key clinical characteristics l characteristics
• Has one or more of the following neurodevelopmental or neurological complications
• Gross motor delay (non-ambulatory or started walking after age 18 months)
• Language delay (non-verbal or started talking after 18 months)
• Altered muscle tone (hypertonia, dystonia, hypotonia)
• Gait difficulties, including stiff gait, short stride, frequent falls, use of orthotics, use of walker
• Tremors
• Microcephaly
• Is a family member of an individual with the above condition
• No restrictions regarding current ambulatory status
• Minimum age for enrollment eligibility will be 6 months due to fragility of neonates with severe forms of DNA repair disorders and limitations of motor assessment scales in infants younger than 6 months. There will be no maximum age for enrollment eligibility.
• No restrictions regarding gender, race, or ethnicity.
• Voluntary written consent from the participant if adult capable of consenting or parent/guardian if minor or not capable of consenting
• Written consent of Legally Authorized Representative if enrolling adult lacks capacity to consent

Exclusion Criteria:

• Any prior history of systemic gene or cell-based therapy
• Current participation in an interventional clinical trial

Any person 6 months or older who is either diagnosed with a DNA repair disorder, or has a family member who is diagnosed with a DNA repair disorder

This study will be conducted in accordance with the following publication and data sharing policies and regulations: National Institutes of Health (NIH) Public Access Policy, which ensures that the public has access to the published results of NIH funded research. It requires scientists to submit final peer-reviewed journal manuscripts that arise from NIH funds to the digital archive PubMed Central upon acceptance for publication.

This study will comply with the NIH Data Sharing Policy and Policy on the Dissemination of NIH-Funded Clinical Trial Information and the Clinical Trials Registration and Results Information Submission rule. As such, this trial will be registered at ClinicalTrials.gov. In addition, every attempt will be made to publish results in peer-reviewed journals.