This study looks at how often cancer happens in people with Parkinson's Disease (PD) who have a special change in their DNA called a *heterozygous mutation* in the **GBA1 gene**. A *heterozygous mutation* means that only one copy of a gene has changed. PD is a disease that affects movement, making it hard for people to control their muscles. The study wants to see if these people get cancer more often than other people. It will compare them to people with idiopathic PD, which means their PD has no known cause, and also to people without PD. The study will check if there's a link between these DNA changes and cancer, and it could help doctors take better care of people with PD by screening for cancer early.

• Study uses data from about 3000 PD patients.
• Only people over 18 with a clear PD diagnosis can join.
• Researchers will use local cancer records to find cancer cases.