I'm sorry your friend's son is going thru this. It's tough for my husband and he is 43 so I can only imagine what a child feels. I also work with a 30 yr old woman who just had both hips replaced due to this disease and she said she took prednisone just a couple of times. Doctors won't swear this is what causes it but when most everyone who has it took steroids at some time then its safe to say its more than a coincidence. Most people who take steroids will never get the disease and some that have it never took steroids. It affects the bone at the joints. You can get it in the hips,shoulders,and knees to name a few. It's painful. My husband had surgery on his right hip and now says he feels it worsening in his left which can mean more surgery later. Make sure your friends get a doctor that is very familiar with AVN/perthes. Our first doctor specializes in hip replacements and we saw another who specializes in CD's so each doctor felt his surgery would work better for the AVN. There are so many different treatments out there for this disease(most surgical) that research is your best option. There are different stages of the disease 1-5(hubby is 4) 5 being collapse of the bone. Usually xrays can't pick it up so if it was diagnosed by xray then it has really gotten bad. (Hubby was stage 3 on his xray and we waited until stage 4 for surgery)One of his legs is now shorter than the other and he limps badly. This disease is not fatal but incurable. Patients live with the fear of it redeveoping in other spots. My best advice to you friends is to learn EVERYTHING they can about this disease and the different surgeries. See which doctors really know their stuff about the disease and get second opinions.The child will have to live with whatever path they take so its best to get all the info available and really drill the doctors. We were told that my husband being so young made him a good candidate for the CD versus the hip replacement(they last about 10 years and have to be redone in some cases) After the problems he has had with the CD(a lot fail and we fear his is failing now) we wish we had chosen the hip replacement. Good luck to your friends and their child. It's a long,scary road but if they are armed with facts and info when they go in its easier to understand the disease. I loved the look on my doctors face when I started talking stages,CD's,hip replacements etc. He changed his tune and realized that we were not going to follow him without questions and that we knew what we were talking about. I'm really surprised we do not have an AVN/Perthes board here. It falls under bone diseases but a search showed very few have mentioned it. Good luck!