The lesson discusses Parkinson’s disease (PD), affecting an estimated 600,000 to 1 million people in the United States, with symptoms typically diagnosed through medical history and physical examination rather than lab tests. Although often considered an older person’s disease, PD can develop in individuals as young as 40, and its impact varies significantly among patients, each experiencing a unique set of symptoms. The decline of dopamine-producing brain cells is central to PD, with research indicating that it may arise from a complex interplay of genetic and environmental factors.