here is some information

Here is what the INS says about it:
Most communicable diseases are easily treatable. If the medical tests are positive for a communicable disease, the Civil Surgeon will recommend a course of treatment. Some medical conditions are not easily treatable. However, you may still receive adjustment of status by filing a waiver application. You are eligible for a waiver if:
You are the spouse or unmarried son or daughter or the minor, unmarried adopted child of a U.S. citizen or LPR; or
You have a son or daughter or lawfully adopted child who is a U.S. citizen or LPR; or
You are eligible for classification as a self-petitioning spouse or child (including your derivative children) because of abuse.