Natural History Study for DNA Repair Disorders

The study coordinator or another team member will review standard health questions relevant to DNA repair disorders. The control group will not undergo an interval history. These questions will include: 1. How the participant's appetite and general weight trajectory has been since the last assessment 2. Any episodes of unexplained bleeding or bruising 3. Any jaundice 4. General level of alertness and interaction with family and others 5. Any changes in cognitive function such as speech, following commands, comprehension 6. Any changes in motor function, including the development of tremors and stiffness in movements

A board-certified neurologist (the principal investigator) will perform a general physical examination and a neurological examination and complete a standard CRF to document relevant findings. The control group will not undergo a physical examination.

An Early Clinical Assessment of Balance (ECAB) will be performed by the physical therapist. Part I can be assessed in all affected individuals, and Part II requires ambulation. For non-ambulatory individuals, only Part I will be applied. The items in the ECAB are summarized as follows: Part I. Head and trunk postural control (maximum 36 points) Head righting - lateral (right and left) Head righting - extension Head righting - flexion Rotation in trunk (right and left) Equilibrium reactions in sitting (right and left) Protective extension - side Protection extension - backward Part II. Sitting and standing postural control (maximum 64 points) Sitting with back unsupported but feet supported on floor or on a stool Sitting to standing Standing unsupported with eyes closed Standing unsupported with feet together Turns 360 degrees Placing alternate foot on the step while standing unsupported

For ambulatory participants, the physical therapist will also assess standardized gait outcome measures, including: 1. Gait Speed: may be measured over a 10 meter distance, assessing both "comfortable" walking speed and "fast" walking speed 2. 10-meter walk/run: timed assessment at fastest gait attainable. This assessment would be omitted for those participants who are determined to have a high fall risk. 3. Timed Up and Go (TUG): time to stand from a chair, walk 3 meters, go around a cone, and return to the chair (with or without an assistive device) 4. Dynamic Gait Index (DGI): assesses 8 balance challenges while walking

Total blood volumes collected at each visit will be limited to 5mL/kg body weight, with a maximum of 18mL. Saliva samples may be obtained if research is taking place where blood samples cannot be drawn or transferred.