Abstract
Mixed connective tissue disease (MCTD) is a rare autoimmune syndrome characterized by overlapping features of systemic sclerosis, systemic lupus erythematosus (SLE), and polymyositis, first described by Sharp et al. in 1972. This case report discusses a 38-year-old female who presented with symptoms indicative of these overlapping conditions, including sclerodactyly, Raynaud's phenomenon, and muscle weakness, confirmed by laboratory findings and imaging. Despite aggressive treatment with immunosuppressive agents such as methotrexate, corticosteroids, and infliximab, the patient's condition progressively deteriorated, leading to severe complications, including interstitial lung disease and gastrointestinal involvement. Mixed connective tissue disease remains a complex and poorly understood condition with a range of clinical presentations and no distinct risk factors. The prognosis varies significantly, with some patients experiencing life-threatening complications while others may achieve complete remission. Diagnostic criteria, such as the Alarcon-Segovia criteria, and serological markers like anti-U1RNP antibodies, are critical in identifying and managing this rare and challenging condition.