How do people treat chromosomal abnormalities?

Chromosomal Abnormal. Chromosomal abnormalities is a broad category. It means there is some gene or genes that are missing or extra. Depending on the particular chromosome affected is the kind of therapy needed. This usually is not something fixed but you can offer modalities to strengthen the weak areas. Usually physical therapy occupational therapy and speech. You work on the problems caused by the abnormality.
Depends. Each chromasome defect has its own set of issues. Some, like down syndrome, or trisomy 21, has a series of health issues. Yet if managed appropriately, an extended lifespan well into the 60's is possible.There is no majic pill to reverse the process as the defect is usually present in every cell in the body. Identification of risks & supportive care are the general approach to care.