Wales and Newport Gwent Dragons hooker Lloyd Burns has been forced to hang up his boots due to a neck injury and possible heart problems.
The 27-year-old has withdrawn from the game completely after a number of tests revealed significant damage to the aorta, which may result in heart surgery.
The club's director of rugby Robert Beale said: "Everything Lloyd has achieved in life he has earned through hard work and dedication, his enforced retirement from the game has come as a massive shock to Lloyd and his family and will resonate throughout the rugby world.
"I am personally relieved that this serious condition has been identified off the field of play and would therefore like to thank our medical team at the Dragons, staff at the Royal Gwent Hospital and University of Wales Cardiff for all their efforts in ensuring Lloyd has and will continue to receive the highest standards of care."
Burns, who began his career with the Dragons in 2008, has been sidelined with the injury since January.