my nephew is 29 months old and he still doesnt speak.he can cay da and bye but thats it we try to help him but it doesnt work.he gets mad really easy but he is really smart.he knows the mop from the broom but im worried about him.he also bites his nails alot and plays with his hands.are these sings of autism?

My sister's son is 3 years old. he seemed to be developing normally but lately seems less attentive and less aware. Seems prone to anger bouts very easily and concentrates on very abstract things. His speech development doesn't seem to be progressing and frankly his relationship building seems even to be arrested. He is very distrubed by any strangers who come in, in a way in which he never was before.

Could this be a sign of autism? he had a triple vaccine a few months ago.