What causes Autism or How is it diagnosed to young children?

My younger brother is four and he is a twin he was born first and he is the one with autism, why did he get it and not my other brother if usually it can be the youngest twin to have any problems or disabilties and how is it diagnosed what are the symptoms or signs to look for.

it is caused by disorder in the brain. you cant cure it

http://en.wikipedia.org/wiki/Autism

I don't know what causes autism, but I have a grandson with autism. He was a very quiet and calm baby, and as he became a toddler he would just go about his business and play in the playroom, and watch his cartoons. Around age 1 1/2 we started wondering a little, because he wouldn't respond to you when you talked to him, or look you in the eye, even though he would give you a hug.They found out that he had frequent ear infections and that he couldn't hear because of it, so they put tubes in his ears, and cleared that up, and he began to hear sound, which was quite overwhelming to him at first. That is when he first began to make sounds.They started looking for more answers and found out through tests that he was autistic, so they learned how to deal with his behavior and how to involve him more in one on one contact, and teach him how to be more involved in personal contact with another person. He went to a special wonderful pre-school that specialized in autism-kids, and he began to progress. Now he is in a autism-geared kindergarten class, and calls us all the time to tell us these long stories what is going on. He is progressing so much, and still have that sweet, kind spirit about him, AND he can now look you in the eye and gives hugs and kisses all the time. The key is that we know what the problem is too, so that we can understand what he is going through, when he is showing frustration, or seem unreasonable on some point. He needs a structured environment, and when he gets away from that for awhile, he does get to a point when he says STOP, "need to go home". Learn as much as you can about autism and how it affects the person. The author Bears Kauffman has written some very good books about their struggle to deal with their son's autism and finding a successful way to deal with it. You can look it up on the internet, if you are interested. His program is also called "the Option Institute". Good luck! Remember, autism is just a fluke in the wireing in the body, just like any other birth defect or body weakness can be. The person underneath it all is still the same wonderful person, and you can find him, if you are willing to put in the homework and learn about it. It will make you a better person and more understanding with other people, as well as with yourself.

Are they identical or fraternal? If they are identical it is rather uncommon (only 20%) for one to be autistic & the other one not.If they are fraternal, there would be no more reason to expect them both to be autistic than to expect you, or any other child born to the same parents to be autistic. (a 6% chance)Genetics is the largest factor in autism but it is obviously not the only factor or you would NEVER have cases where one identical twin is autistic & the other is not.Many suspect the vaccinations at about 18 months cause autism. This is only a possiblity in about 20% of the cases. There was a study using home old videos taken at first & 2nd birthday parties. About 20% of the autistic kids developed normally the first year & regressed by the 2nd birthday. So it is not impossible that those 20% "got" their autism from the vaccinations. But I think it is unlikely that all of that 20% would have the same cause.How young are the boys? Lack of eye contact is one of the biggest things to look for. Autistic children are also very unlikely to imitate as normal kids do. Rocking & flapping their hands in from of thier face is a classic symptom.