Disorders of the skin and mucous membranes play an important role in the clinical presentation of HIV infection. In increasing immunosuppression in HIV infection, many diseases of the skin and mucous membranes tend to become more severe, disseminated, and associated with visceral organ involvement, leading to the death of patients. The authors present a clinical case of disseminated Kaposi sarcoma (KS) with internal organ (lung) involvement in a patient with HIV infection. Typically, patients with HIV-positive status develop KS in the presence of severe immunodeficiency (CD4⁺ lymphocytes <200 cells/μL), but this was not the case for this patient (CD4⁺ lymphocytes were >360 cells/μL), which corresponded to a moderate immunodeficiency state. Despite the etiopathogenetic and supportive therapy, the patient’s underlying disease worsened due to the progression of respiratory and cardiovascular failure, and in 20 days, the patient died. Pathological and histological studies showed multiple SK foci in the lungs. The clinical case shows no absolute correlation between cutaneous and visceral manifestations of SK.Differential diagnosis was made between polysegmental pneumonia, pulmonary tuberculosis, and disseminated KS. The authors discuss the possible causes of disseminated KS in a young HIV-infected patient. Predictors of fatal outcomes include multimorbidity, fulminant pulmonary KS, anemia, thrombocytopenia, leukocytosis, and hemodilution.. In addition, an immune reconstitution inflammatory syndrome induced by initiated intensive multicomponent antiretroviral therapy may be assumed. This clinical case suggests that KS may affect lung tissue with mild to moderate KS manifestations on the skin and oral mucous membranes. Pulmonary involvement in KS is rare but often fatal.