Introduction and aim. Autoimmune rheumatic diseases are a group of disorders with similar clinical, laboratory and immunological manifestations. Connective tissue diseases include systemic scleroderma, dermatomyositis or polymyositis, Sjögren’s syndrome, rheumatoid arthritis, and systemic lupus erythematosus. If the patient meets the diagnostic criteria for at least two of these diseases and has specific serologic markers, a diagnosis of overlap syndrome is possible. Description of the case. This case describes a 27-year-old man who had a history of paroxysmal fever, night sweats, erythema-like skin lesions on the forearms and lower legs, a feeling of progressive muscle weakness especially in the proximal muscles, and dry mouth. The patient was diagnosed with an overlap syndrome: systemic lupus erythematosus, dermatomyositis, and Sjögren’s syndrome. Conclusion. Overlap syndrome is difficult to treat due to its multisystem nature, requiring a symptomatic therapeutic approach and careful control of medication doses to reduce side effects while controlling disease activity.