Wales hooker Lloyd Burns has been forced to retire with immediate effect.
The 27-year-old Dragons front-rower has been out of action since January with a neck injury, having completed a rapid rise to prominence prior to last year's Rugby World Cup.
The Dragons have now revealed that "ongoing tests" have shown aorta damage, with possible heart surgery to follow, forcing Burns' premature retirement.
In the space of 18 months Burns rose from Welsh Premiership level to the Dragons regional side, making his Wales debut against the Barbarians in Cardiff last June.
He went on to play seven Tests, including four at the World Cup, before being advised to take at least three months out due to a neck problem.
"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," Dragons director of rugby Robert Beale said.
"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 or all their efforts."