A Rare Case of Rhupus Syndrome: Evolution from Systemic Lupus Erythematosus with Secondary Immune Thrombocytopenic Purpura to Rheumatoid Arthritis Overlap

Background: Rhupus syndrome is a rare overlap syndrome characterized by coexistence of systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). The syndrome has an estimated prevalence of 0.01-2% among patients with rheumatic diseases and presents unique diagnostic and therapeutic challenges. Case Presentation: We report a case of a 31-year-old female who initially presented in September 2023 with fever, heavy menstrual bleeding, thrombocytopenia, and positive antinuclear antibodies (ANA). She was diagnosed with SLE complicated by secondary immune thrombocytopenic purpura (ITP) and treated with intravenous immunoglobulin (IVIG), hydroxychloroquine, and oral corticosteroids. After two years of stable disease, she developed symmetric polyarthritis with morning stiffness and significantly elevated rheumatoid factor (166.64 IU/mL), leading to the diagnosis of rhupus syndrome. Discussion: This case illustrates the natural progression from SLE with secondary ITP to the development of erosive rheumatoid arthritis, a rare but well-documented phenomenon. The patient's clinical course demonstrates the classic temporal pattern where SLE manifestations precede RA symptoms by several years. Laboratory findings including elevated inflammatory markers, positive anti-nuclear antibodies, and significantly elevated rheumatoid factor support the diagnosis of rhupus syndrome. Conclusion: Rhupus syndrome remains a diagnostic challenge requiring high clinical suspicion. Early recognition and appropriate management with disease-modifying antirheumatic drugs can help prevent joint destruction and improve long-term outcomes. This case adds to the limited literature on the evolution of SLE to rhupus syndrome.