Before the handshake that may have saved his life, Mark Gurrieri thought his hands were getting bigger because of too much DIY and working in his restaurant kitchen. But a chance meeting with a doctor revealed the growth was related to a rare disease which could have cost him his sight.

Alarm bells rang for GP Chris Britt when he spotted Gurrieri's fleshy hand and large features. Gurrieri, 36, had acromegaly, a condition caused by excessive growth hormone from the pituitary gland, usually prompted by a tumour, that affects three in a million people.

Last month the restaurant owner had an operation to remove most of the tumour at the base of his brain. "My mum thinks Chris is my guardian angel," said Gurrieri, from Loughton, Essex.

Gurrieri's friend, Rob Thompson, had taken Britt to lunch at the Amerigo Vespucci at Canary Wharf, east London, in December. Thompson introduced the pair, who shook hands at the door.

Gurrieri said. "He didn't say anything to me but he turned to my friend and said 'I am sure he has acromegaly'."

Gurrieri, divorced with a seven-year-old son, said he had been feeling unwell and would fall asleep at a moment's notice. "I always had big hands, but I noticed in recent years they had become quite chunky. I put it down to DIY at home and working in the kitchen. I had noticed my face becoming more fleshy too."

Doctors estimated he had had the condition, which can lead to blindness, diabetes and heart problems, for four or five years. Britt, a GP in Woodford Green, north-east London, said he had not seen a case since he was a student. "When I was at Bart's (St Bartholemew's) hospital in London I saw a few people with the condition because it is a specialist centre."