A member asked:

Is the genetic test for huntingtons disease 100% accurate? my grandmother had huntingtons, and my mother was having what she thought were symptoms, so she got tested. the test was negative. can we be completely she doesnt have it, which means i dont e

7 doctors weighed in across 2 answers
Dr. Herbert Krob answered

Specializes 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 10/3/2016


Dr. Scott McLean answered

Specializes in Clinical Genetics

Excellent question: Huntington disease is a serious condition - genetic testing can be extremely helpful. Good information is here: http://www.hdsa.org/. No test is perfect, but the test for HD is 99.9% accurate. To know for sure if your mom had the right test, and to get more info, see a genetic counselor or a clinical geneticist, and take a copy of the test results with you.

Answered 5/23/2016



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