GBA1 and Parkinson disease: Later, with dedicated research and numerous contributions, most notably by Ellen Sidransky from the NIH, and particularly her meta-analysis from 2009 (which confirmed an odds ratio of 5.43 for each GBA1 variant in PD patients compared to controls) [2], GBA1-related PD became an established entity with the following three unique features compared to idiopathic PD: an earlier age of onset, a more severe clinical course, and a higher likelihood of developing dementia [3].