ATXN2 and obesity due to melanocortin 4 receptor deficiency: In addition to causing SCA2 and increasing the risk of developing ALS, mutations in ATXN2 may play a role in a handful of other diseases, including Parkinson’s disease (PD), spinocerebellar ataxia type I (SCA1), Machado-Joseph Disease (SCA3), tauopathies, primary open-angle glaucoma (POAG), obesity and type I diabetes.