Comedian and actor Richard Lewis, 75, recently announced in a Twitter video that he was diagnosed with Parkinson’s disease two years ago.

"I started walking a little stiffly, I was shuffling my feet, so I went to a neurologist and they gave me a brain scan, and I was diagnosed with Parkinson’s disease," he shared in the video.

The "Curb Your Enthusiasm" star appeared optimistic about the fact that he was diagnosed with the central nervous system disorder later in life, at 73 years old.

RICHARD LEWIS REVEALS PARKINSON'S DISEASE DIAGNOSIS: 'I'M FINISHED WITH STAND-UP'

"Luckily, I got it late in life … I’m on the right meds — so I’m cool," the actor said.

Late-onset vs. early-onset Parkinson’s

While the majority of people with Parkinson’s disease are diagnosed after age 60, some develop it earlier in life.

When a person is diagnosed at 50 years old or younger, it is considered early-onset Parkinson’s disease, according to the Parkinson’s Foundation.

When it afflicts someone older than 50, the disease is considered late-onset. 

What's relatively the same across all age groups are early motor symptoms such as tremors, stiffness, slowness of movement, fatigue, depression, anxiety, loss of smell and trouble sleeping, among others.

Early-onset Parkinson’s more likely to be hereditary

While it’s possible for someone to get early-onset Parkinson’s disease even if it doesn’t run in the family, the younger cases are more likely to be hereditary, according to Dr. Charalampos Tzoulis, professor of neurology and neurogenetics at the University of Bergen and Haukeland University Hospital in Norway.

"Such causes include mutations in genes such as PRKN (Parkin) and PINK1," the doctor told Fox News Digital. 

Richard Lewis

Comedian and actor Richard Lewis, 75, recently announced in a Twitter video that he was diagnosed with Parkinson’s disease two years ago. (Getty Images)

About 15% of those with Parkinson’s have a family history of the disease, per Johns Hopkins Medicine.

These cases are caused by genetic mutations in the genes LRRK2, PARK2, PARK7, PINK1 or SNCA.

Outcomes of early-onset Parkinson's

Actor Michael J. Fox, who is now 61, was diagnosed with Parkinson's disease in 1991 at just 29 years old (he didn't share his diagnosis publicly until 1998). 

In 2000, he started the Fox Foundation for Parkinson's Research, which is dedicated to finding a cure for the disease through funding and research of therapies. Fox has also written four memoirs since his diagnosis.

Michael J. Fox gives a speech at the podium at the Governors Award

Michael J. Fox (pictured accepting the Jean Hersholt Humanitarian Award) was diagnosed with early-onset Parkinson's disease in 1991 at age 29. (Kevin Winter)

One advantage of getting Parkinson’s early in life is that it tends to progress more slowly, said Dr. Tzoulis, who also leads research on Parkinson’s disease and other neurodegenerative disorders.

"Early-onset Parkinson’s generally progresses slower and may have a better long-term prognosis," said the doctor. 

Younger patients are also less likely to have dementia or cognitive problems. 

"But the prognosis depends on multiple factors, such as whether there is a genetic cause and what the individual's response is to dopaminergic therapy (medications that regulate dopamine levels in the brain) as well as comorbidity."

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Younger patients are also less likely to have dementia or cognitive problems, and they tend to live significantly longer than people with older-onset Parkinson’s, said Dr. Joel S. Perlmutter, a professor of neurology at the Washington University School of Medicine in St. Louis, Missouri, in a webinar for the American Parkinson Disease Association (APDA).

There are, however, some drawbacks to getting Parkinson’s earlier in life.

Woman holding hand

Younger patients with Parkinson's disease are less likely to have dementia or cognitive problems; they tend to live significantly longer than people with older-onset Parkinson’s. But there are drawbacks, too, for a diagnosis earlier in life.  (iStock)

"Younger patients are more prone to developing levodopa-induced dyskinesias (involuntary movements) during the course of the disease," Dr. Tzoulis told Fox News Digital. 

This effect is caused by the long-term use of levodopa, which is the most common medication for managing Parkinson's motor symptoms.

"Early-onset Parkinson’s generally progresses slower."

"This can often be effectively handled by advanced treatment options, such as deep brain stimulation," the doctor added.

Patients with early-onset Parkinson’s are also more likely to develop dystonia, which causes involuntary muscle contractions and changes in posture.

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Depression and anxiety can also be heightened with earlier diagnoses.

"People with young-onset Parkinson’s tend to have a higher rate of depression than older onset Parkinson’s," said Dr. Perlmutter.

Life expectancy with Parkinson’s

Parkinson’s is not in itself a fatal disease, according to the APDA. 

"Most patients die with Parkinson’s disease and not from it," the foundation stated on its website. 

"The illnesses that kill most people are the same as those that kill people with PD. These are heart conditions, stroke and cancer."

Caregiver

Overall, people with Parkinson’s potentially can live as long as they would without the disorder. (iStock)

As the disease progresses, however, it can make someone more susceptible to accidents and other conditions that could become fatal.

For example, those with Parkinson’s have a higher risk of falling. 

They could be up to three times more likely to experience falls, per a 2021 study in Journal of Movement Disorders.

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People with the disorder also face a higher danger of developing pneumonia (lung infections) due to difficulty swallowing. 

Those with early-onset Parkinson's tend to have higher rates of depression.

Aspiration pneumonia — which occurs when someone breathes food or liquid into the airways or lungs without swallowing — accounts for 70% of deaths in people with Parkinson’s disease, a 2021 study published in Scientific Reports found.

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Overall, however, those with Parkinson’s can potentially live as long as they would without the disorder.

"Related complications" may reduce overall life expectancy by just one to two years, Healthline stated.