Dominic Patrick, aged 14 (Merseyside, UK) spent the whole day playing computer games while on his knees. He needed hospital treatment for a blood clot in his leg.

It had been a rainy day and he decided to stay inside and play with a games console.

Doctors said his DVT (deep vein thrombosis) was caused by having his legs tucked under his body for so long.

DVT is usually linked to older people who spend long periods without moving - it is rare in younger people.

The boy noticed that when he got up he had pins-and-needles and one calf was swollen.

His dad thought he had 'growing pains'. When the boy was eventually taken to hospital the doctor diagnosed DVT.

He has been prescribed a long course of warfarin (blood-thinnin drug).

In Thailand, the authorities proposed a curfew on online gaming between 10pm and 6am amid fears of both 'addiction' to role-playing games, and the dangers of marathon sessions.

Mandatory play breaks every two hours were also proposed as a way of cutting the risk of DVTs.

Dr Russell Keenan, a paediatric haematologist from the Alder Hey Children's Hospital in Liverpoo (UK)l, said that it was extremely unusual to see DVTs in otherwise fit and healthy children.

He said: 'I would expect to see a DVT in a child perhaps once every few weeks - but the vast majority of these involve children who are very seriously-ill in other ways.

'The only risk factor we could find in this case was the fact that Dominic had sat on his legs for 10 hours playing computer games without moving.

'If you fold the leg, you are basically folding the vein in the leg and causing the blood supply to stagnate. That is what might be causing the clot.

'However, it doesn't mean that the government should be putting health warnings on Playstations.'

View drug information on Warfarin Sodium tablets.