Asperger's Syndrome (AS) is a…well…a syndrome. But have you ever thought what a syndrome actually is and what qualifies something as being a syndrome?
A syndrome is something that is indicated by a group of symptoms for which the actual cause is not known. So imagine we didn't know about the influenza virus, but people would be seen to suffer the symptoms of fever, sore throat and muscle pains at the same time; we can class these as a group of symptoms. If the root cause of what causes this group of symptoms wasn't known (ie the influenza virus) then we'd class this phenomenon as a "syndrome" as we recognise that the group of symptoms must mean something is wrong, but we don't know what that "something" is.
We do know about the influenza virus, though, so flu is not a syndrome at all but a disease. However look at AIDS. AIDS is "Acquired Immune Deficiency Syndrome"…yep, a syndrome. When AIDS first came out we recognised the symptoms (a greatly reduced immune system giving rise to numerous conditions rarely seen in healthy people) but no-one knew the actual cause so it was classed as a syndrome. After much research the cause of AIDS was found…the HIV virus. So AIDS is no-longer officially a syndrome. This leads us nicely to another point…when a syndrome's name is very well known and wide-spread and the cause is eventually found we tend to just leave the name as it is even if it is no longer a syndrome.
Getting back to Asperger's Syndrome, if someone has the symptoms of impaired social interaction, impairment of non-verbal behaviour, failure to develop appropriate peer relationships, lack of desire to share enjoyment and lack of emotional reciprocity we recognise that group of symptoms as meaning that person has Asperger's Syndrome; however we don't know the actual cause of the impairments - remember that no-one knows the cause of autism yet. When the cause of AS is finally discovered we can be quite sure the name won't change though, it will always be called Asperger's Syndrome even if one day it ceases to be one.