Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. Much research is being done to find the cause(s) of systemic juvenile rheumatoid arthritis, but to date, it is not known. One cannot say that living in a house with mold is the reason the person has systemic juvenile rheumatoid arthritis. I am sorry your son has this severe type of juvenile rheumatoid arthritis. Is he receiving the best possible medical care? What kind of doctor follows him? There are many new treatments for this condition and they are known to the pediatric rheumatologist. Do you live near a university medical hospital? Because this medical facility is the best place to find this type of doctor. Also, should your son need care for other body parts, at this same hospital will be pediatric cardiologist, pediatric lung specialist, pediatric bone specialist, pediatric eye specialist, and physical therapists who work with children. Hope I have answered your query. Let me know if I can assist you further.