What causes Juvenile Huntington disease ?
What causes Juvenile Huntington disease (HD)? Mutations in the HTT gene cause Huntington disease. The HTT gene provides instructions for making a protein called huntingtin. Although the function of this protein is unknown, it appears to play an important role in nerve cells (neurons) in the brain. When the huntingtin protein is abnormally made, it is thought to lead to the death of neurons in certain areas of the brain, which causes the signs and symptoms of Juvenile HD. The HTT mutation that causes Huntington disease involves a DNA segment known as a CAG trinucleotide repeat. This segment is made up of a series of three DNA building blocks (cytosine, adenine, and guanine) that appear multiple times in a row. Normally, the CAG segment is repeated 10 to 35 times within the gene. In people with juvenile HD, the CAG segment is repeated more than 60 times.