NOTE:Read Jackson's full letter to his supporters here.
Rev. Jesse Jackson's announcement Friday that he has been diagnosed with Parkinson's disease came as a surprise to many, but his diagnosis was apparently not a secret to all.
Though he had not publicly announced it, Northwestern Medicine said Jackson was diagnosed with the disease in 2015. He has been treated as an outpatient in the years since, the hospital said.
Congressman Danny Davis (D-Chicago) added that those close to Jackson "have noticed some of the signs."
The 76-year-old civil rights leader and prominent religious and political figure announced the news in an emotional letter to supporters Friday.
"For me, a Parkinson's diagnosis is not a stop sign but rather a signal that I must make lifestyle changes and dedicate myself to physical therapy in hopes of slowing the disease’s progression," he wrote.
Jackson's father also suffered from the disease.
Parkinson's disease is an uncurable neurodegenerative disorder that affects movement, according to the Mayo Clinic. It can lead to tremors, slowed movement, rigid muscles, loss of movement and speech changes.
Jackson is known for his work as a civil rights activist with Rev. Martin Luther King Jr. and as a Democratic presidential candidate in the 1980s. He founded Chicago's Rainbow PUSH coalition and has remained a prominent religious and political figure, continuing his outspoken activism recently following the fatal shooting of 17-year-old Laquan McDonald in Chicago. He also spoke out about police shootings nationwide, including in Ferguson, Missouri.