Dentatorubral-pallidoluysian atrophy (DRPLA) and Huntington’s disease (HD) are rare genetic disorders affecting the brain, caused by a specific type of genetic change, an elongation of a repetitive stretch of the letters “C-A-G”. In DRPLA that expansion is found in the Atrophin-1 gene, while in HD, it affects the Huntingtin gene. Both conditions are part of a group of at least nine diseases caused by similar genetic changes, each associated with a different gene.
DRPLA and HD cause a range of neurological symptoms due to the degeneration of brain cells, but they affect different brain regions. Both HD and DRPLA are associated with changes in deep parts of the brain called the “basal ganglia”, which can lead to jerky, dance-like movements. DRPLA also impacts a brain region called the cerebellum, which helps regulate the correction of movements, and so deterioration of this brain region presents with a type of clumsy movement called “ataxia”, which is rarely seen in HD. HD symptoms usually appear between ages 30 and 50, whereas DRPLA has a broader age range. Both conditions worsen over time.
DRPLA and HD share many similarities. Both are inherited from an affected parent, giving each children a 50% risk of developing the condition. They also exhibit anticipation, meaning symptoms tend to appear earlier in each generation. Unfortunately, neither has treatments that alter their progression, so management focuses on symptom relief.