• Loss of dopamine-producing neurons in the substantia nigra.
• Lewy bodies and alpha-synuclein aggregation leading to cellular dysfunction.
• Mitochondrial dysfunction and oxidative stress leading to neuronal death.
• Dysregulation of motor pathways in the basal ganglia, causing motor symptoms.
• Neuroinflammation contributing to the progressive loss of neurons.
• Genetic factors influencing familial forms of the disease.

Together, these processes lead to the clinical symptoms of Parkinson’s disease, including the hallmark motor symptoms as well as a wide array of non-motor symptoms.