Tennis legend Monica Seles shared that she has been diagnosed with myasthenia gravis, an autoimmune disease with symptoms she first noticed while doing what she loves the most — playing tennis.

Monica Seles first noticed the symptoms of myasthenia gravis — a neuromuscular autoimmune disease — while she was swinging a racket the way she’d done so many times.

Nine-time Grand Slam champion Monica Seles is battling a new challenge: a neuromuscular autoimmune disease called myasthenia gravis.