Parkinson's disease (also known as Parkinson disease, Parkinson's, idiopathic parkinsonism, primary parkinsonism, PD, or paralysis agitans) is a degenerative disorder of the central nervous system. The motor symptoms of Parkinson's disease result from the death of dopamine-generating cells in the substantia nigra, a region of the midbrain; the cause of this cell death is unknown. Early in the course of the disease, the most obvious symptoms are movement-related; these include shaking, rigidity, slowness of movement and difficulty with walking and gait. Later, cognitive and behavioural problems may arise, with dementia commonly occurring in the advanced stages of the disease. Other symptoms include sensory, sleep and emotional problems. PD is more common in the elderly, with most cases occurring after the age of 50.

The main motor symptoms are collectively called parkinsonism, or a "parkinsonian syndrome". Parkinson's disease is often defined as a parkinsonian syndrome that is idiopathic (having no known cause), although some atypical cases have a genetic origin. Many risk and protective factors have been investigated: the clearest evidence is for an increased risk of PD in people exposed to certain pesticides and a reduced risk in tobacco smokers. The pathology of the disease is characterized by the accumulation of a protein called alpha-synuclein into inclusions called Lewy bodies in neurons, and from insufficient formation and activity of dopamine produced in certain neurons within parts of the midbrain. Lewy bodies are the pathological hallmark of the idiopathic disorder, and the distribution of the Lewy bodies throughout the Parkinsonian brain varies from one individual to another. The anatomical distribution of the Lewy bodies is often directly related to the expression and degree of the clinical symptoms of each individual. Diagnosis of typical cases is mainly based on symptoms, with tests such as neuroimaging being used for confirmation.

Michael J. Fox, OC (born Michael Andrew Fox; June 9, 1961) is a Canadian American actor, author, celebrity, producer, activist and voice-over artist. With a film and television career spanning from the late 1970s, Fox's roles have included Marty McFly from the Back to the Future trilogy (1985–1990); Alex P. Keaton from Family Ties (1982–1989) for which he won three Emmy Awards and a Golden Globe Award; and Mike Flaherty from Spin City (1996–2000), for which he won an Emmy, three Golden Globes, and two Screen Actors Guild Awards.

Fox was diagnosed with Parkinson's disease in 1991, and disclosed his condition to the public in 1998. Fox semi-retired from acting in 2000 as the symptoms of his disease worsened. He has since become an activist for research toward finding a cure. This led him to create the Michael J. Fox Foundation, and on March 5, 2010, Sweden's Karolinska Institutet gave him a honoris causa doctorate for his work in advocating a cure for Parkinson's disease.

Since 2000 Fox has mainly worked as a voice-over actor in films such as Stuart Little and Atlantis: The Lost Empire, and taken guest TV roles such as in Boston Legal, The Good Wife, Scrubs, Curb Your Enthusiasm and Rescue Me. He has also released three books, Lucky Man: A Memoir (2002); Always Looking Up: The Adventures of an Incurable Optimist (2009); and A Funny Thing Happened on the Way to the Future: Twists and Turns and Lessons Learned (2010). He was inducted as an Officer of the Order of Canada on May 27, 2011, for his outreach and fundraising work.