My 6 year old was hard to understand from day 1
My first child, when he was just born, didn't have any sucking instinct. The formula had to be fed by a syringe and he had a severe reflux problem - projectile vomiting - and had to sleep, while held up by either me or my husband. He was extremely sensitive to light and looked as if he couldn't breath if he saw the sunlight.
He couldn't jump until almost 3 and couldn't speak a word until well past 3rd birthday. (However, he's an early reader - almost started speaking and reading at the same time) He never wanted to play at the playground and just observe other kids and still has a bit of social problem, not understanding the social cues. He didn't show much empathy to anyone, but is getting better slowly through "learning."
His fine motor skill was always bad, but improved a lot by practicing. (my husband is extremely clumsy, knocking everything on the dinner table all the time, too) His gross motor skill still needs a lot of improvement. His speech and intellectual cognition is now well above average, but his social skill is delayed and his poor motor skill (e.g. can't catch a ball) doesn't help him at the playground either. His preschool teacher was wonderful and nurturing. The 1st grade teacher is more critical and puzzled by this imbalance. We are working together to encourage confidence in sports and friendship.
Having said all the symptoms I could match from the checklist, I knew he doesn't have autism and have always been frustrated, but never knew such disorder exists... I think everyone has to some degree of sensory imbalance and maybe patience and willingness to work through with your child will benefit more than labeling a disorder. I know I could have been much better if I had been more patient and creative.