Differential Diagnosis for Mediastinal and Hilar Lymphadenopathy in a 73-year-old Male with HIV, HTN, and Elevated PSA

Single Most Likely Diagnosis

• Lymphoma: Given the patient's HIV status, which compromises the immune system, and the presence of significant lymphadenopathy in the mediastinal and hilar regions, lymphoma is a highly plausible diagnosis. HIV-associated lymphomas, particularly non-Hodgkin lymphoma, are more aggressive and can present with widespread lymphadenopathy.

Other Likely Diagnoses

• Tuberculosis (TB): Although less common in the context of the provided findings, TB can cause lymphadenopathy, especially in immunocompromised patients like those with HIV. The presence of hilar and mediastinal lymphadenopathy could suggest a diagnosis of TB, particularly if the patient has been exposed or has risk factors.
• Sarcoidosis: This condition can cause bilateral hilar lymphadenopathy and can also involve the mediastinal lymph nodes. While it's less directly linked to HIV, sarcoidosis can occur in anyone and should be considered, especially if other systemic symptoms are present.
• Metastatic Cancer: Given the elevated PSA, prostate cancer with metastasis to lymph nodes is a possibility. Although prostate cancer typically metastasizes to bones, lymph node involvement, especially in advanced disease, can occur.

Do Not Miss Diagnoses

• Pneumocystis jirovecii Pneumonia (PCP): In HIV patients, especially those with significant immunosuppression, PCP is a critical diagnosis not to miss. While it primarily causes pulmonary symptoms, it can also lead to lymphadenopathy in some cases.
• Kaposi's Sarcoma: Another HIV-associated condition that can cause lymphadenopathy, although it more commonly presents with skin lesions and visceral involvement.

Rare Diagnoses

• Castleman Disease: A rare disorder that can cause lymphadenopathy, including in the mediastinum. It's more commonly associated with HIV and can present with systemic symptoms.
• Lymphoproliferative Disorders: Other rare conditions, such as Castleman disease or angioimmunoblastic T-cell lymphoma, can also present with lymphadenopathy but are less common and might require specific diagnostic criteria to be considered.

Each of these diagnoses requires careful consideration of the patient's clinical presentation, laboratory findings (including the CD4 count and viral load for HIV), and imaging characteristics. A definitive diagnosis often relies on histopathological examination of the affected lymph nodes.