Molecular pathology selected abstracts
October 2024—Huntington disease is a neurodegenerative disease caused by abnormal CAG trinucleotide repeats in exon one of the HTT gene, in which the number of CAG repeats affects disease presentation. Alleles with 40 or more CAG (cytosine, adenine, guanine) repeats are fully penetrant and age at disease onset is inversely correlated with number of repeats, while 36 to 39 CAG repeats are associated with reduced penetrance and fewer than 36 are not considered to cause Huntington disease. It is thought that inherited CAG repeats may undergo somatic expansion until a harmful threshold is reached before the degenerative process begins.