My middle son is now 11, and has a milder from of NOMID. He has been on Ilaris for over 2 years (the shot you are talking about) and it is wonderful! He was on daily injections of anakinra from 4.5 yrs until almost 9, when he switched to the Ilaris.
Before he was on medications, he was like your son almost every other day, and was miserable. He has NOMID, so he got brain pressure, and had some pressure in the optic nerve and also had some risk to his hearing, and all that reveresed within months of starting medications. He had stopped growing from the age of 3 until going on medications at 4.5 years of age, but has now caught up on height and weight, and lives a very active, normal life now with almost no issues.
He has to take a much higher dose of the Ilaris than MWS of FCAS patients, and has had a few breakthrough symptoms whenever he has needed to go up onto a higher dose, but most of his days are free of suffering. He can focus in school well, and is advanced on his school tests. Before medications, he was so tired, and weak and could not even handle preschool due to the fevers, anemia, headaches, pain and frequent vomiting with flares.
Call me if you want to talk- I also run The NOMID Alliance, www.nomidalliance.net and have talked with many CAPS patients and their families from around the world that are in the same position as your son.
The concern with CAPS is the effects of long-term inflammation affecting the body, such as hearing loss and also the frequent suffering that can affect kids greatly as they get older. These medications will change his life. Many patients say, "I now know what normal feels like" after starting medications, since they have known nothing but suffering their entire lives.
The earlier you start medications, the better the odds of avoiding hearing loss or other concerning complications, and also your child will have a better quality of life and self-esteem. There is great stigma to being a patient, and having everyone ask about your rash, or why you cannot do things like everyone else. If we had known what my son had earlier, or if medications were even available, I would have started even sooner.
At the time, he was the youngest going on anakinra at the NIH, but within a few years, younger patients were being diagnosed sooner, and started on medications. Currently, many infants have been started on anakinra, some even within the first few months of life if they have significant symptoms, and are diagnosed.
My son has NOMID, so he was at great risk if he did not start medications but he is on the milder end, so some now feel like he is more like a crossover of MWS and NOMID. No matter what form of CAPS, patients suffer greatly and with these new medications they can have a chance to experience life like everyone else.
Have you also found http://www.rarediseasecommunities.org/en which is a great new network site for CAPS patients that is moderated by staff from EURODIS and NORD? It is helpful too, and there are many medical articles on the site as well.