The actor who played Scotty in the original Star Trek TV series and films,
James M Doohan, has been diagnosed with Alzheimer's disease.
Doohan played Lt Cdr Montgomery "Scotty" Scott in the first Star Trek series
The 84-year-old learned he had the progressive neurological disorder "within the last couple months", his agent Steven Stevens said.
Doohan also has Parkinson's disease, diabetes and fibrosis.
Living in Seattle, he appeared in the original 1960s Star Trek TV series and seven Star Trek films.
His career spans more than 50 years, but he remains best known for his role as the USS Enterprise's affable chief engineer, Lt Cdr Montgomery "Scotty" Scott.
Doohan also served as a solider in the Canadian military during World War II.
His son Chris Doohan said his father's Alzheimer's diagnosis stemmed from his father's increasing loss of short-term memory.
"His long-term memory seems to be intact," he said.
"If you ask him how he got his role on Star Trek or [about] D-Day, he can talk for an hour about that. But if you ask him what he had for breakfast, he can't say."
Stevens, who has represented Doohan for 28 years, said the actor made a cameo appearance in forthcoming horror movie Skinwalker: Curse of the Shaman in January.
Doohan reprised his role as Scotty in seven Star Trek movies
"He didn't have any energy and he seemed very frail," Stevens said, "but as soon as they yelled 'action', he was the same old feisty Scotty."
The actor lives in Redmond, Seattle, with his wife Wende and three children. He also has four children from a previous marriage, Stevens said.
Doohan plans to attend a three-day Star Trek farewell convention in Hollywood from 28 August, with co-stars William Shatner and Leonard Nimoy.
Doohan is also due to receive a star on the Hollywood
Walk of Fame on 31 August.