Annette Funicello, an iconic former child star from Disney's "Mickey Mouse Club" in the 1950s, has died at the age of 70 from complications of chronic progressive multiple sclerosis, a disease she had been battling for over two decades.

The Walt Disney Company reported that Funicello passed away peacefully at Mercy Southwest Hospital in Bakersfield, California, at the age of 70.

Extra reported that Funicello passed away after her family finally took her off life support after several years in a coma induced by progressive multiple sclerosis. She is survived by her husband, three children from her first marriage, and three grandchildren.

"She's on her toes dancing in heaven... no more MS," Funicello's daughter Gina Gilardi said in a prepared statement. "My brothers and I were there, holding her sweet hands when she left us."

Multiple sclerosis (MS) is an inflammatory neurological disease in which myelin, the protective layer that insulates neuron cells in the nervous system, gradually degenerates. As myelin degrades in different parts of the brain, people with MS can experience varying symptoms like fatigue and tingling sensations, and develop sensory, muscle coordination, and memory problems.

Most people do not experience severe symptoms, though in progressive cases like Funicello's, muscle paralysis can lead to a debilitating decline in quality of life.

"MS does not directly shorten the lifespan," explained Dr. Rhonda Voskuhl, director of the MS program at UCLA, to Today.com. "It doesn't kill people directly. If you've had a very severe form for a very, very long time you can have the same complications that anyone has who is immobilized. You can get pneumonia. You can get bed sores. You can have difficulty eating."

At least one in 1,000 have multiple sclerosis, according to the National Institute of Neurological Disorders and Stroke, and most people develop their first symptoms between the ages of 20 and 40. There is no cure, though promising therapies can limit relapses and slow down the condition's progression if it is diagnosed in early stages. Unfortunately for Funicello, such MS treatments were not developed early enough to prevent her decline.

Funicello, who began her acting career at age 12, became "America's Sweetheart" as an original Disney Mouseketeer, and went on to star in the teen-oriented Beach Party films and record a series of hit singles throughout the 1960s.

She was diagnosed with multiple sclerosis in 1987 at the age of 50, and kept her illness private until publicly disclosing it in 1992, when she established The Annette Funicello Research Fund for Neurological Diseases.  The charity, which funds research into the cause, treatment, and cure of neurological disorders like multiple sclerosis, is still active.

Funicello's autobiography, A Dream Is a Wish Your Heart Makes, chronicled her struggle with multiple sclerosis and was made into a TV movie in 1995.

As she became increasingly debilitated with multiple sclerosis by the late 1990s, Funicello rarely appeared in public. She was cared for primarily by her second husband, the rancher Glen Holt, whom she married in 1986. According to Extra, she lost the ability to walk in 2004, and to speak in 2009.

Canada's CTV featured Funicello and her husband in a feature on her progressive multiple sclerosis last year, highlighting a controversial experimental treatment for her condition that was ultimately unsuccessful. At that point, she was fed through a tube and required round-the-clock care.

 "[Annette] will forever hold a place in our hearts as one of Walt Disney's brightest stars, delighting an entire generation of baby boomers with her jubilant personality and endless talent," said Disney CEO Bob Iger in the company's official statement.

"Annette was well known for being as beautiful inside as she was on the outside, and she faced her physical challenges with dignity, bravery and grace."

You can watch video footage of Annette Funicello's late-stage struggle with multiple sclerosis at CTV.