Systemic lupus erythematosus (SLE) is one of the most complex rheumatic diseases, which is due to the variety of its clinical forms and manifestations. The article describes a case of severe lung injury (LI) in a female patient with previously undiagnosed and untreated SLE, which led to a fatal outcome. A 33-year-old female patient diagnosed with pneumonia was delivered by an ambulance team to City Clinical Hospital Thirteen. Her leading complaints were dyspnea, joint pain, fever, and abdominal pain. During examination of the patient and analysis of her medical documents, attention was focused on a long history of articular syndrome, recurrent pneumonia with progressive pulmonary hypertension, general trophic, hematological changes, and the presence of autoantibodies, which was in aggregate the basis for the diagnosis of SLE with LI. This clinical case demonstrates the importance of the timely diagnosis and treatment initiation of SLE with LI. The diagnosis of SLE requires special attention to the patient's history and clinical and laboratory parameters. Specific immunological studies were conducted in doubtful cases. Rheumatological alertness is necessary, especially in relation to young women.