Child with disorder question

There's a little boy in my class that is VERY bright. He's doing basic addition up to 20, knows the alphabet, can write his first and last name.. which is great for a 4 year old. However, he has a processing problem somewhere. My husband remembered that there is something out there that matches him, but couldnt' remember what it was. Basically, the boy has a hard time expressing feelings/thoughts. If something upsets him he will tend to react by throwing a fit, or otherwise being non-cooperative. For someone just looking in, it looks like he's trying to get attention. If you watch him long enough, though, you can tell that it's not intentional. He simply doesn't know how to connect what's in his brain with words. However, from what his karate instructor told me, she NEVER sees that problem. He has recently gotten county assistance with someone coming in twice a week to work with him and observe, but if anyone knows the name for this disorder, please drop me a note and let me know.