A few months ago my bright, active 4 year old started to limp. As a hospital paediatrician, I ignored it and thought he was being melodramatic. After a few weeks, I decided that perhaps he had hurt himself and needed an x ray. So I duly took him to my work, and asked one of our juniors to arrange radiography, which was normal. He limped on for a couple more weeks until one day my medical family noticed that his right ankle was hot and swollen. This was intermittent, and by the time he saw another of my colleagues, it was back to normal. A couple more weeks passed, during which time the ankle was hot and swollen, and he could only hop. We were seen as a favour in orthopaedic outpatients, where the opinion was that this was most likely to be juvenile idiopathic arthritis. Within a week we had started down the arthritis road, and …