It depends which category your relative is applying under.
Contrary to what some people think, HIV is not considered a danger to public health and safety.
The only issue is excessive demand on the medical system.
However, if your relative is either the SPOUSE or DEPENDENT CHILD being sponsored by his/her parents, then excessive demand rules DO NOT apply so your relative can still get PR status.
If he/she is being sponsored by someone other than her spouse or parents then excessive demand rules DO apply and he/she may not be eligible for PR.
I would suggest that you read this document on HIV and Canada Immigration for more information: http://www.hivimmigration.ca/Publications/FAQ%20on%20HIV%20Immigration%202005.pdf