Muhammad Ali has been hospitalized after experiencing respiratory issues.

A family spokesperson announced that Ali, 74, is currently being treated by doctors and was in fair condition as of Thursday afternoon.

“Ali, who suffers from Parkinson’s disease, is being treated by his team of doctors and is in fair condition,” family spokesman Bob Gunnell said in a statement to WDRB-TV in Louisville. “A brief hospital stay is expected. At this time, the Muhammad Ali family respectfully requests privacy.”

Ali first rose to prominence when he became the the heavyweight champion at just 22-year-old by beating Sonny Liston in 1964. He’s widely regarded as one of the best boxers and athletes in sports history.

In a message of support on Twitter, Sugar Ray Leonard issued a statement. "Prayers and blessings to my idol, my friend and without question, the Greatest of All Time," Leonard wrote.

Last year, the former heavyweight boxing legend was hospitalized with a urinary track infection, and back in 2014, he experienced a mild case of pneumonia but was able to make a full recovery.