Muhammad Ali was being treated in a hospital Thursday for a respiratory issue, according to a spokesman for the legendary heavyweight boxer.

The spokesman, Bob Gunnell, told the Associated Press that Ali was in fair condition and was being treated as a precaution. Gunnell did not specify where Ali was being treated or when he was admitted. But Gunnell said the hospitalization was expected to be brief.

Ali, 74, was diagnosed with Parkinson’s disease in 1984.

Ali was hospitalized in 2015 with a urinary tract infection after being found unresponsive at his home in Scottsdale, Arizona. In December 2014, he was treated at a hospital for pneumonia.

In recent years, Ali has kept a relatively low profile, compared to his younger years, when he was renowned for belittling his opponents and taking controversial political stances. He last fought in 1981, losing a unanimous decision to Trevor Berbick, a year after getting pummeled by Larry Holmes at a time when many pleaded with him to retire.

Before the end of his career, though, Ali carved out a place in boxing lore as the self-described “greatest of all-time,” a title with which plenty of fans and analysts agree. Beginning his pro career in 1960, the Louisville native first won the heavyweight title in 1964, in a stunning upset of Sonny Liston. A second match-up took place in Lewiston, Maine, in 1965.

Stripped of his title in 1967 for his refusal to enter the draft for the Vietnam War, Ali would not fight again until 1970.

He suffered his first loss in 1971, in the first of three epic battles against Joe Frazier, before regaining his title in 1974’s “Rumble in the Jungle” against George Foreman.

All told, Ali finished with a record of 56-5, including 37 wins by knockout.