Hello All!  My story is similar to many of yours however we know we are a bit different in our disorder/disease.  My name I Nikki and I'm guessing my IA/MCAD started manifesting when I was 18. I'm 39 now so it's been a journey.  I had severe chest pain and became allergic to shellfish when I was 18. These both came on about the same time. Um?  I was always a bit tired and had bouts of anemia growing up but didn't give it much thought. When I was six weeks into my second pregnancy at 25 all hell broke loose and the anaphylactic reactions started for no apparent reason. The docs said it was probably the hormone change and should return to normal within a few weeks after delivery.  After delivery, things did clear up but I had ana reactions every month when my estrogen levels increased. After two years I had a hysterectomy.  Things improved but then started to slide again.  I have reacted to many, many things but of course my IGE tests all come back negative. The severe chest pain that I had at 18 came back with a vegenance and has never left. The docs said costochondoritis.  About six years ago the knee pain started.  I also began noticing all my symptoms really flared up in the spring/fall and following an illness.  I was diagnosed with IA and sent to Northwestern's Allergy Clinic in Chicago. They put me on Ketoifen and I've been taking that  for the past six years.  I thought I had made it through the fall this year scott free and then at the beginning of Dec I had the flu.  Still I thought I was home free as this was my first fall in years that I had not had an ana attack.  Well that changed on Dec 20.  Since then I have been a wreck. Last week I went to Mayo and and was diagnosed with IA versus MCAS.  Basically my doc said that there is a lot of overlap between the two so they will be measuring urine levels when I have reactions.
Let me mention my brother, only sibling, died from anaphylaxis at age 22 aprox 15 years ago. He had been a severe asthmatic since age 2 and allergic to peanuts since age 1. He had been in a near fatal car accident in May 1995 and had the entire summer off work. During his summer off he had two seperate surgeries (lung and knee) as a result of the accident.  In August just about the time he was considered recovered, he was hit by a car on his pedal bike.  In Sept he went back to work,  his long-time gf move out, and was put on an antibiotic for an infection (prob from the surgeries) Two weeks upon returning to work, he ate something in the cafe that had hidden peanut butter in it and died.  They had onsite paramedics that administered epi but and tried desperately to save him but he just could not fight it off.  Looking at his life, I would guess he had masto but back then nobody knew anything about this rare diease. I had never heard of ana shock until he died. Who would have thought a year and a half later, I would be living his life.  
I have a lot to live for and I'm on going to tackle this disorder head on.  Glad to meet you all!

I agree.  My brother was absolutely in worse shape than I am.  He passed 15 years ago and started his ill path 36 years ago so at that time they just didn't know what they know now.  The years have been kind to us through medical research and breakthrus.  I have suffered for many years and am seeing signs in my youngest child so I decided enough is enough, I have to find out what is wrong with me for not only my sake but for the sake of my children and grandchildren.  It is a very scary situation when the attacks strike but I am looking forward to a more stable future by connecting with the right medical community and support groups such as this one. Knowledge is power.