HD related diseases are all neurodegenerative disorders with similar and partly overlapping clinical features, or caused by genetic mechanisms characterized by similar biological traits.
Some neurodegenerative diseases of the cerebellum, called ominant Spinocerebellar Ataxia (SCAs), may be associated with similar genetic traits (expansion of DNA traits), though present in different genes, causing symptoms sometimes similar and indistinguishable from chorea. For example, SCA17 or Dentato-rubral pallidoluysian atrophy (DRPLA) may present symptoms very similar to Chorea and a genetic cause that is also due to the expansion of the CAG tract, but in different genes. The list of these very rare diseases is growing year by year and today many of these lesser-known diseases than Huntington, called by acronyms such as SCA1, SCA2, SCA3 etc..., can provide insights for the fight against Chorea and, on the other hand, might in turn benefit from future innovative therapies effective for Huntington, once they become available.
On the other hand, other diseases better known to the scientific community, such as atypical forms of Parkinson's disease, dementia of the Alzheimer type or familial dystonia syndromes (such as Wilson's disease), may also represent 'related diseases', as their symptoms are similar to those of chorea. Therefore, Huntington's disease is considered by the leading international regulatory authorities (such as the FDA) as an important model of study whose gain of knowledge will pave the way to an improved therapeutic approach also for many other more known and incurable diseases.