HIV infection can lead to a number of oral symptoms, including those that affect your tongue. However, these symptoms occur only in later stages of HIV, and the only way to know your status before specific symptoms of HIV occur is through HIV testing.
Pseudomembranous candidiasis (thrush) and erythematous candidiasis are two fungal infections that can affect an HIV-positive person's tongue. Thrush appears as white plaques that you can remove, while erythematous candidiasis is a series of flat and red patches that can appear on your tongue.
For someone with HIV, oral herpes occurs only rarely inside the mouth, and even more rarely on the tongue. However, blisters may sometimes develop on the top side of the tongue.
Oral Hairy Leukoplakia
An HIV-positive individual may develop oral hairy leukoplakia--immobile, ridged white growths that may appear to be hairy. Their cause is opportunistic infection with Epstein-Barr virus.
Kaposi's sarcoma, an AIDS-defining condition, is a skin cancer causing purple (or other dark) lesions. Opportunistic infection with the virus HHV-8 causes Kaposi's sarcoma. It can sometimes appear on the tongue.
Some symptoms of HIV on the tongue respond well to the general treatment for HIV, antiretroviral drugs. However, you need to target some symptoms more specifically--as with antiviral, antifungal or cancer treatments--so you should seek a physician's advice to obtain proper treatment.