Abstract
RATIONALE: Systemic lupus erythematosus (SLE) is a chronic autoimmune disease that affects multiple organ systems. Retroperitoneal fibrosis (RPF) is a rare condition characterized by the development of fibrous tissue in the retroperitoneal space. The coexistence of SLE and RPF is extremely uncommon, and this report aims to enhance understanding of this complex relationship. PATIENT CONCERNS: A 32-year-old woman presented with sudden-onset syncope. Her medical history revealed a 5-year history of SLE, and imaging studies identified a retroperitoneal mass. DIAGNOSES: A comprehensive diagnostic workup, including magnetic resonance imaging (MRI) and biopsy, confirmed retroperitoneal fibrosis secondary to SLE. INTERVENTIONS: The patient was treated with high-dose corticosteroids, immunosuppressive therapy, and the biologic agent rituximab. OUTCOMES: The patient's symptoms markedly improved, and follow-up MRI demonstrated significant regression of the retroperitoneal lesion. LESSONS: RPF associated with SLE is exceptionally rare. This case underscores the importance of early diagnosis and a coordinated multidisciplinary approach in managing such complex conditions. Glucocorticoid therapy remains the cornerstone of treatment, augmented by immunosuppressants and biologic agents when necessary.