Which disease can result from untreated HIV infection?

The disease that results from untreated HIV infection is AIDS, which stands for Acquired Immunodeficiency Syndrome. When an individual is infected with HIV, the virus attacks the immune system, specifically targeting CD4+ T cells, which are crucial for the body’s ability to fight infections. If left untreated, the progressive damage to the immune system diminishes the body's defenses over time, leading to AIDS.

AIDS is characterized by the development of certain opportunistic infections and cancers that occur due to the weakened immune system. The transition from HIV infection to AIDS typically occurs within several years if the infection is not managed with antiretroviral therapy. This highlights the importance of early diagnosis and treatment of HIV to prevent the progression to AIDS and to maintain immune function.

The other options listed—diabetes, hepatitis, and Alzheimer's disease—are unrelated to untreated HIV infection and arise from different causes, such as lifestyle factors, other viral infections, or neurodegenerative processes, respectively. Thus, AIDS is the correct choice as it directly results from the chronic effects of untreated HIV.