Wow, that's interesting to see/hear of Kawasaki twice in just a few days now when it was an "unknown" when my son had it. He was 18 months old when he woke up with a huge red swollen rash on his neck and chest on a Friday. Got in to see the dr that afternoon, they gave him antibiotics or something and had us see the dr who would be on call the next day and we returned as it did not subside. My son could not turn his head as his neck was so sore and swollen. Anyway we were checked into the hospital that day and spent 5 days 4 nights there in December of '03.
They never knew what exactly it was, I only know it was Kawasaki (not confirmed though) because a month later I mentioned something that was really odd to my family (his palms and soles peeled as if he'd had a bad sunburn, I think this was about 2 weeks after he'd been sick). My cousin, who was visiting my family and is an Army pediatric cardiologist, immediately recognized the symptoms I described and the rash in the photo and told us it was Kawasaki's and to check his heart. So we did, fortunately all was well. He is now going on 7 and doing just fine.
All the symptoms fit from what I saw when I researched Kawasaki's online except for the "strawberry tongue" which I dont know about. Everything else yep. Age (peak age is 18 months) gender (more boys than girls get it) rash soreness/stiffness all the rest, I dont remember them all now.
Anyway, due to the hospital/doctor not identifying it as Kawasaki at the time, I dont know about the treatment protocol. I would feel better if you had a pediatric cardiologist involved tho. Maybe your regular doctor/hospital is aware and doing the right thing but 5 1/2 years ago they did not recognize it in my son. (We were in Turlock then. Good doctors, they just didnt know about this.) Also your son is only 7 months old - not saying it couldn't be Kawasaki, but that is young. A pediatric cardiologist would be more positive in confirming or ruling out whether it is Kawasaki's disease, and ensure you have the proper followup needed. (Hopefully you wont need prolonged care - only about 25% do if I remember right. But if you are in this group, you are fortunate to know of it now and get it treated. It is outgrown by age 6 I think.)