NEW YORK -- Tennis great Monica Seles has revealed she was diagnosed with myasthenia gravis -- a chronic neuromuscular autoimmune disease, also known as MG -- three years ago.

Ahead of the 2025 U.S. Open, which kicks off next week in Flushing Meadows-Corona Park, the 51-year-old Hall of Famer opened up about her health journey for the first time.

"It took me quite some time to really absorb it, speak openly about it, because it's a difficult one. It affects my day-to-day life quite a lot," she told the Associated Press.

Seles -- whose career included nine Grand Slam titles, seven of them before she turned 19 -- revealed she was referred to a neurologist after first noticing symptoms such as double vision and weakness in her arms and legs.

"I would be playing with some kids or family members, and I would miss a ball. I was like, 'Yeah, I see two balls.' These are obviously symptoms that you can't ignore," said the Yugoslavia native.

She added that everyday activities like blowing out her hair "became very difficult" as a result.

Seles said she plans to attend the U.S. Open later this month, in partnership with an event with immunology company Argenx aimed at raising awareness about MG.

According to the Cleveland Clinic, myasthenia gravis can also target muscles in the face and neck with symptoms including difficulty speaking, swallowing or chewing.

MG happens when the body's immune system mistakenly attacks itself, though the cause of the condition is unclear.

"Studies suggest that certain immune system cells in your thymus gland have trouble identifying what's a threat to your body (like bacteria or viruses) versus healthy components," the clinic adds.

MG is incurable, according to the National Institute of Neurological Disorders and Stroke, but can be treated through thymus gland removal surgery, lifestyle changes and more.

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