As a matter of fact the name itself speaks to what it is. It's called Acquired Immune Deficiency Syndrome. It means an immune deficiency that is acquired in some way. It is a syndrome. A syndrome is, think of alcoholism.
Alcoholism is a syndrome.
We know the cause. It's drinking too much. But it can have a spectrum of consequences that aren't necessarily going to show up in each individual. In some people alcoholism affects their central nervous system, some people it affects their liver, they get cirrhosis, some people have gastrointestinal problems. There are all sorts of things that can be a consequence of alcoholism.