Patients with Human Immunodeficiency Virus (HIV) who initiate Antiretroviral Therapy (ART) at advanced stages of the disease frequently develop Immune Reconstitution Inflammatory Syndrome (IRIS). This process is associated with the activation of the immune response, which can lead to paradoxical exacerbation of opportunistic infections or the unmasking/onset of malignancies such as Kaposi's sarcoma and Non-Hodgkin Lymphoma (NHL). In the case we present, the onset of primary mediastinal large B-cell lymphoma occurred in the context of IRIS.

Furthermore, lymphadenopathy arising as part of IRIS presents a significant diagnostic challenge, as it may be misinterpreted as a relapse of a previously treated malignancy. The situation is compounded by the potential for viral mutations that reduce the efficacy of ART and the development of neurological complications, such as HIV encephalitis, whose symptoms also require differential diagnosis.

This clinical case illustrates not only these diagnostic difficulties but also the induction of an oncological process itself amidst immune recovery, necessitating a comprehensive approach that includes careful monitoring of virological and immunological dynamics.

Thus, the presented observation not only demonstrates the complexity of managing patients with IRIS but also emphasizes the global importance of controlling HIV infection. Timely initiation of antiretroviral therapy is a key factor in preventing severe complications, including malignancies. Concurrently, strict monitoring of already infected patients is essential, including through the creation of specialized registries to study long-term outcomes. A fundamental role in addressing this problem is played by widespread promotion of measures for the prevention of HIV infection.

Galimat Radjabova graduated from Sechenov University in 2024. She is currently completing a residency in pediatric oncology at the Russian Medical Academy of Continuing Education. She has over 10 publications.