Suzanne,
I had to think long and hard about answering your post b/c it opens a huge can of worms I do not desire to open. But laying in bed, remembering sitting where you are, I have to. Yes, in short, the MMR is very much known to be a factor in ITP. It's also a factor in any number of autoimmune diseases b/c it damages the immune system. I have three vaccine damaged children. All given shots up to age 12mos (the MMR being the last). I would highly encourage you to do some serious study on if you want to continue vaccinating your children. Start with Dr. Sherry Tenpenny and from there you can branch out (Dr. Mercola and others). Study both sides. Be informed, because your doctor will NOT inform you (especially of both sides of the equation). Vaccines are damaging to the immune system. Natural immunity is always a better method of immunity. We vaccinate to "save" a very small number of children/adults affected by diseases compared to the massive amounts of damage done from the shots themselves.
I have three kids. One with major nervous system damage, one with major gut damage (my ITP kid), and one with mild nervous system damage from shots. All very easily connected to when and what shots they received.
What I DO want to encourage you is that vaccine damage can be "undone." While it will not remove immunity (although many of these viruses are now mutating and the current shots may not provide immunity to the mutated viruses) you can help the body remove the damage. We have used homeopathy with all three of my children and seen tremendous reversal in the damage caused by the shots they had. The MMR being the most damaging to them. In the case of my son's ITP, it was critical that we dealt with it as it was a huge factor in his getting ITP. While we are mostly through the ITP now (still have the occasional bump in the road - although not often), we are still continuing to work on detoxing out the vaccine damage. For my ITP boy, we had to deal with mulitple layers of vaccine damage, drug damage (pred./IVIG/benadryl) before we could even get him above zero platelets. And while it was a slow process of getting him back into the normal range, the h-pathy did get us there. He still bobbles once in awhile but we're a far cry from the zero that we sat at for what felt like forever (months).
So when it comes to healing ITP as a result of vaccine damage (really, it's immune system damage caused by the vaccine), do not let anyone tell you it's not possible. It IS possible. And while people like to say that most children are acute ITP cases and it most likely will go away - I haven't seen that. When ITP results from vaccine damage, I see more often then not they become chronic because that shot doesn't magically leave the body nor does the body magically fix the immune system damage. I do see where cases of ITP caused by odd viruses, etc. being mostly acute. But that goes against the grain of what everyone spouts so do with it what you will.
But the short answer to your question is "yes," the MMR very well could have been a factor in ITP and I personally would not do it for another child since they carry similar genes and factors. Because while the next child might not get ITP, you may end up with nervous system damage (tics, MS, etc.) or something else (have a friend whose boy got JRA from the MMR).
The bottom line is, do your research. Research ALL sides of the vaccine issue. When you are done, you can at least feel confident in whatever decision you make. Because ultimately, you have to feel like you're doing the right thing for your family. If you're here wondering, it's probably a good indicator that more research for future vaccination is worth the time and effort.
And my last thought is this - when I was researching (started after #2 had MMR damage) I began to research the actual ingredients to many of these shots. I soon realized that if I were to take an empty syringe, fill it with attenuated virus (which simply means weakened, not dead), added ethylene glycol (anti-freeze), a little mercury (my kid's shots had mercury), formaldahyde (preservative used in embalming), and a few other ingredients, and shot that into my child's thigh - I'd go to jail for child abuse. But have a doctor do it and it's called a vaccine.
Food for thought............