Final answer:
The opportunistic disease associated with AIDS, characterized by hyperpigmented lesions, is Kaposi's sarcoma. It surfaces as a result of the weakened immune system in AIDS patients and is caused by the human herpesvirus 8.
Step-by-step explanation:
Opportunistic Disease Associated with AIDS
The opportunistic disease associated with AIDS that is characterized by hyperpigmented lesions of the skin, lungs, and GI tract is Kaposi's sarcoma. Kaposi's sarcoma is a type of cancer that is most commonly found in patients with AIDS. It forms red, raised, scab-like skin lesions and is caused by a type of herpes virus - the human herpesvirus 8 (HHV-8) - which usually does not cause illness in people with a healthy immune system. However, in AIDS patients, due to their weakened immune systems, this virus can lead to aggressive cancer growth.
People living with AIDS are particularly vulnerable to opportunistic infections and cancers because the virus severely damages the immune system, notably reducing CD4 T-cell counts to very low levels. As a result, conditions like Kaposi's sarcoma, which was once a rare and relatively subdued disease in the elderly, emerged as a severe illness in young AIDS patients with compromised immune systems, as observed in the early 1980s.