A 23-year-old male with HIV/AIDS and mpox who had initiated anti-retroviral therapy (ART) 3 months prior presented with dysphagia from an enlarging oral lesion. Physical exam revealed a large bleeding friable mass overlapping the incisors and canines, extensive diffuse non-tender lymphadenopathy, and multiple scattered crusted facial lesions (Fig. 1). Computed tomography showed extensive cystic/necrotic cervical, supraclavicular, and mediastinal adenopathy with ulceration/necrosis of the palatine tonsils. Biopsies of the lymph nodes and oral mass were positive for Kaposi sarcoma (KS). Due to the recent initiation of ART, the rapid progression of the disease, and the disseminated nature, this was determined to be due to immune reconstitution inflammatory syndrome (IRIS).

Figure 1
figure 1

Photo of patient described in case on day of admission to the hospital

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IRIS is an exaggerated inflammatory response after the initiation or change in ART therapy.1 A flare of KS due to IRIS is referred to as KS-IRIS and presents in two forms: paradoxical (existing KS) and unmasked (undiagnosed KS).2 KS initially presents as a purple nodule/plaque that can progress to disseminated KS involving lymph nodes and the gastrointestinal tract.3 Until biopsy, the differential diagnosis includes bacillary angiomatosis, angiosarcoma, or hemangiomas. KS can cause pain and bleeding at the local tumor but lung or oral involvement can cause life-threatening respiratory distress requiring urgent management.4,5