Meet the 11-year-old boy with a rare life-threatening disease that means he can't go out in the sun without breaking into a severe rash and his throat can swell so much it almost closes over. Damon Muller has almost doubled in size due to swelling and bloating since he was diagnosed with Juvenile Dermatomyositis (JDM) in November - a rare autoimmune disease that can only be treated with high doses of steroids and a chemotherapy-type drug. The disease has robbed Damon, from Gladstone in central Queensland, of the ability to run, ride his bike and play outside freely in the sun - something his mother Nicci Moynahan says has been very difficult. Damon Muller has almost doubled in size due to swelling and bloating since he was diagnosed with Juvenile Dermatomyositis (JDM) in November - a rare autoimmune disease . 'He has gone from an active kid to barely being able to move in just five months,' Ms Moynahan told Daily Mail Australia. 'He has basically doubled in size... he has gained a lot of weight due to the side effects of his medication and he has severe stretch marks on his legs.' JDM effects and limits movement in the muscles closest to the trunk of Damon's body, including his thighs, hips, buttocks, chest, shoulders and upper arms. He has already been rushed to hospital once after his  neck started swelling so much it almost closed his throat and there is a risk his heart could be impacted too. 'It is very scary, we just don't know what to expect. There’s no way of knowing how long this will go on for and when it could flair back up again,' Ms Moynahan said. 'He has to be wary of the sun for the rest of his life.' JDM effects and limits movement in the muscles closest to the trunk of Damon's body and he has already been rushed to hospital once after his neck started swelling so much it almost closed his throat . The disease has robbed 11-year-old Damon, from Gladstone in Queensland, of the ability to run, ride his bike and play outside freely in the sun due to side effects of his condition . The medication used to treat his condition means he can have severe reactions if he has direct contact with the sun like this infected rash on his thigh . The medication used to treat his condition means he can have severe reactions if he has direct contact with the sun. 'He can longer play outside in the sun without being completely covered. He has to stay inside most of the time and I let him out in the late afternoon from say 4pm,' Ms Moynahan said. 'The UV rays makes his skin rashes much worse and could also send him back to hospital. 'He loved playing outside, on the trampoline, riding his bike and running around - he can't even go outside to play at school.' Damon was diagnosed with JDM back in November after several trips to various doctors throughout Queensland. He had been complaining of aching limbs for a while before he started to develop bright red rashes on his legs and body. Damon was diagnosed with JDM back in November after he started complaining of aching limbs and developed bright red rashes on his legs and body . The rash, visible here on his face, was what tipped his parents off that there could be something wrong . Damon, pictured with younger brother Toby, has doubled in size due to swelling and bloating as a result of his medication. His disease can only be treated with high doses of steroids and a chemotherapy-type drug . 'The rash was out of control by that stage… it had spread to his face. Between his thighs started looking infected and he was complaining of leg pain,' Ms Moynahan said. 'He woke up with temperatures and he was blowing up. He couldn’t move his arms, he couldn’t dry himself, wipe himself.' Blood tests confirmed the rare autoimmune disease and he was put on steroids immediately. 'He was struggling to walk at the beginning. His legs would tire within seconds and he has collapsed a couple of times just trying to turn around or walk,' Ms Moynahan said. 'They raised him to 60mg of steroids a day at one point and since then he’s gone from a gorgeous kid to someone with a very round face and tummy and his thighs have stretch marks from bloating and swelling.' The medication used to treat his condition means he can have severe reactions if he has direct contact with the sun so he is forced to stay indoors . Damon - pictured here with mum Nicci, dad Daniel and little brother Toby - had complained about aching limbs before bright red rashes started to appear across his body . Damon's parents say there isn't much information or support available in Australia for his disease and are hopeful they will be able to attend an annual conference held in America for the Cure JM Foundation next January. The family have set up a crowd-funding website to help get there. 'We’re only five months in and it’s been an adjustment. There's no way of knowing what is to come,' Ms Moynahan said. 'There's nothing in Australia for this disease with kids so I want to find out more information. It will also give Damon a chance to interact with other children the same as him.' For more information Damon's disease and his crowd-funding, visit www.mycause.com.au.
Damon Muller was diagnosed with rare autoimmune disease in November .
The 11-year-old can't go out in the sun or be active due to muscle swelling .
He was rushed to a Brisbane hospital because his throat closed over and there's a chance his heart could be affected too .
Juvenile Dermatomyositis effects muscles including thighs, hips and chest .