At what age can a child reliably be diagnosed with PDD? [View All]

[merwin]

My son started getting words around 1 year old, had about 5 of them that he would say regularly and then something happened. Probably a huge coincidence, but shortly after one of his big rounds of vaccines, he went back to not talking at all. Now he just turned 2 years old and has some issues that I see as potentially troubleshooting. People tell me it's just the terrible two phase, but this is something that's been pretty constant since about a year and a half.

He doesn't speak. He will occasionally make elephant and train noises if asked. He grunts, points, or whines if he wants something. He frequently slaps himself or bangs his head against things when he gets even slightly upset (which can happen very easily). He doesn't get upset when actually does hurt himself (bump his head into the metal support under our desk), fall down and skin his knees, etc. He gets insanely focused on the task at hand sometimes, which usually involves trains, cars, or his Nick Jr shows, requiring us to say his name 4 or 5 times for him to look over at us and acknowledge that we exist. He is almost impossible to divert from his current task. For example, if we are outside and need to go inside, he will flip out.

The thing that gets me the most is that he understands EVERYTHING you say, but won't talk at all. For example, if I lay out 3 board books that look the same, one of which is Go Dog Go, and ask which one is Go Dog Go, he will pick the right one. He will point out any Dora character that you ask for. He will flip through pages until he finds the elephant, etc.

I do understand that much of this can be explained away with the "terrible two's", but when I put it all together it seems troubling to me.