I get asked this question a lot so I thought this link would help:
Sensory Processing Disorder and Auditory Processing Disorder fall under this category. Isaac has aspects of both. If you catch him on a "bad day" it is very clear that Isaac is different. He's oversensitive to his surroundings, has trouble communicating or doesn't communicate at all, he can be aggressive, his play becomes very rigid and repetitive, and he has odd "stimming" behaviors like spinning in circles, hand-flapping, and chewing and drooling (he's three) on days like this. On a good day, he may seem pretty normal- as long as you only ask the limited questions he will actually answer. Friends who have known us for awhile can each probably share a story of what Isaac was like before the gluten-free/dairy free diet and therapies. In fact, feel free to share a memory below.
Also, I found this article in Time about Sensory Processing Disorder that should help clear things up for those who are interested: