**Question:** An HIV infected patient is showing following oral lesions. The causative organism is-

A. Candida albicans
B. Herpes simplex virus
C. Human papillomavirus
D. Kaposi's sarcoma

**Core Concept:**
Oral lesions in HIV-infected patients can be caused by various pathogens. HIV weakens the immune system, particularly affecting T-cells, leading to a higher risk of opportunistic infections and malignancies.

**Why the Correct Answer is Right:**
In the context of oral lesions in HIV-infected patients, the correct answer is D. Kaposi's sarcoma. Kaposi's sarcoma is a malignant tumor that affects skin, mucous membranes, and other organs in HIV-infected individuals. It is caused by the Kaposi's sarcoma-associated herpesvirus (KSHV), a member of the herpesvirus family. KSHV infects endothelial cells and leads to uncontrolled cell proliferation, which results in the formation of the characteristic spindle cell lesions seen in Kaposi's sarcoma.

**Why Each Wrong Option is Incorrect:**
A. Candida albicans (Option A) is a common oral fungal infection seen in immunocompromised patients, including HIV-infected individuals. However, it is not the causative agent for Kaposi's sarcoma.

B. Herpes simplex virus (Option B) is responsible for oral herpes infections (HSV-1 and HSV-2) but not Kaposi's sarcoma, which is caused by KSHV.

C. Human papillomavirus (Option C) is associated with oral warts and cervical cancer, not Kaposi's sarcoma, which is caused by KSHV.

**Clinical Pearl:**
Oral lesions in HIV-infected patients are a crucial aspect of clinical assessment, as they may indicate the progression of HIV infection and the development of opportunistic infections or malignancies. Early recognition and prompt initiation of antiretroviral therapy can help to improve the patient's prognosis.