ANDRIES Pretorius has been forced to retire from professional rugby with immediate effect on medical grounds after being diagnosed with a rare autoimmune disorder at the age of 29.

After joining Worcester Warriors last summer from Cardiff Blues, where he had been club captain, the twice-capped Wales international sustained multiple inexplicable calf tears during pre-season training.

During September and October last year, the tears started to appear in other body parts and, as a result, the club sent Pretorius to see a nerve conduction specialist and a neurologist.

At that stage, he was diagnosed with Neuromyotonia, or Isaacs’ Syndrome, a disorder which causes muscles to continuously cramp, preventing them from recovering after exercise.

Warriors supported Pretorius by dedicating extensive resources and staff to better understand his condition as well as giving the player extra time to overcome the disorder.

However, the rarity of the disorder means current treatments are not guaranteed to eliminate the symptoms.

After multiple bouts of different treatments were found to be ineffective, Pretorius was left with no option other than to retire to ensure he can continue to live as normal a life as possible. Pretorius said: “It is with great sadness that I have to announce my retirement from rugby.

"Unfortunately, due to the disorder, I can't perform to the standard I know is required to push myself and my team-mates without hurting myself.

“I must thank Worcester Warriors, and their medical department in particular, for the endless amount of support they have provided over the last five months.

"No one had dealt with something like this before but they kept me positive and really did everything they could. I will always be very grateful for their support.

“I wish everyone at Warriors all the best for the rest of the season and for what is going to be a very exciting period in the club’s history.”

Warriors' high performance director Nick Johnston said: “We have worked closely with Andries over the last five months and exhausted every avenue to understand his disorder and offer the best medical support possible.

“Andries is unable to train and play at the intensity required to maintain a career in professional rugby without exposing himself to a high level of risk and has therefore taken the decision to announce his retirement.

“Andries’ well-being is of paramount importance and his overall health must be the priority in this situation.”

Warriors' director of rugby Dean Ryan said: “Andries’ disorder meant he was never able to play his part in the progression of this club on the pitch during his time here but his day-to-day attitude was something which was a positive influence on other players.