Everyone is born with the Huntington gene. Huntington’s disease is caused by an abnormal copy of the gene that is passed from parent to child. HD occurs only when a person is born with the abnormal gene and may then pass it on to their children. Every person who carries the abnormal gene will eventually develop symptoms if they live long enough.
Soon after the HD gene was identified in 1993, a specific gene test was developed which allows a person to find out if they carry the abnormal HD gene and will someday develop the disease. The test is very accurate but it cannot determine when the symptoms of the disease will begin or how severe the symptoms will be. People who test positive for the gene and do not have symptoms of HD may remain unaffected for many years.