Lots of stuff is misdiagnosed. Jenny McCarthy's child was diagnosed as having autism. Thus began her misguided promotion that vaccinations causes autism. After several years, it turned out to be food allergies. Her child was not autistic. But, like many, once invested in the lie, they can't stop repeating it.
First off, I am going to be the last one to tell people to "do your own research", because quite frankly, most people don't know how to do research, or evaluate the sources of their information, but what I will say, is it is OK to question any physicians diagnosis. Ask them, why do you think this is what it is? Are there other possibilities? What rules them out? Etc. It's always good to get a second opinion.
Secondly, I had a physician tell me that sometimes, a physician will give a diagnosis of something like Exercise induced asthma or ADHD because the parent won't take "it's normal, he's a kid" for an answer. Yes, a doctor told me that. I asked another doctor about that, and he confirmed it.
You know what they call the person that graduates at the bottom of their class in medical school? Doctor.
In closing, I have seen someone have an exercise induced asthma attack. It was scary. I've also seen a mom run up to a kid and give him his inhaler because he was breathing heavy after a 100 yd dash. He wasn't breathing any heavier than I was.