I have been diagnosed with MCTD for at least 3 years now and with Raynaud's for a bit longer. My ANA went up by steps but only to either 640 or 1280 (I can't remember...my next appointment is coming up!). However, it was completely normal at my last appointment for the first time in at least 4-5 years (it took me a while from my first positive to get the diagnosis of MCTD). I know your son's is higher, but hopefully it would be possible for him too. I don't know how long he's been diagnosed, but my Raynaud's was quite bad the first 8-12 months I was diagnosed, but has been much, much better since then.