A member asked:
Is the genetic test for huntington’s disease 100% accurate? My grandmother had huntington’s, and my mother was having what she thought were symptoms, so she got tested. The test was negative. Can we be completely she doesn’t have it, which means i don’t e
1 doctor answer
Dr. Herbert Krob answered
28 years experience in Neurology
Huntington's : Huntington's disease is a complicated neurodegenerative disorder that can cause involuntary writhing, dance-like movements of the limbs, other abnormal movements, personality changes and psychiatric symptoms, heart disease and other problems. It is an uncommon condition (about 5-10 cases per 100000 people). Huntington's disease is caused by a mutation in the huntingtin gene. Inside this gene is a stretch of dna that consists of repeating sequences the genetic code letters, or nucelotides, c, a, and g. These three nucleotides can be repeated (cagcagcag...) dozens of times. The number of "trinucleotide repeats" seems to determine if and when the disease will make itself known. People with less than 28 repeats are normal. People with 28 to 35 repeats are "intermediate". People with 35 to 40 repeats may or may not develop huntington's disease. People with more than 40 repeats will be affected, and the higher the number of repeats, the earlier the disease starts. Gene tests for huntington's disease are not usually reported as "positive" or "negative". They usually report the number of trinucleotide repeats that are present. It is not common for children of people with a normal number of repeats to spontaneously develop huntington's disease.
Answered on Oct 3, 2016
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