Polyglutamine disorders are a group of neurodegenerative diseases caused by the abnormal expansion of CAG trinucleotide repeats in specific genes, leading to the production of proteins with extended polyglutamine tracts that are toxic to neurons. These disorders, including Huntington's disease and several spinocerebellar ataxias, are characterized by progressive neuronal dysfunction and loss, resulting in a wide range of motor, cognitive, and psychiatric symptoms.