A Case Report of Mixed Connective Tissue Disease Predominantly Manifesting as Systemic Sclerosis in a Middle-Aged Nepali Woman

Introduction: Mixed connective tissue disease (MCTD) is a rare systemic autoimmune disorder, first described in 1972, that presents with overlapping features of systemic lupus erythematosus, systemic sclerosis, and polymyositis. The diagnosis of MCTD is complex and often delayed due to its varied clinical manifestations and the requirement of serological confirmation, particularly the presence of anti-U1 RNP antibodies. Despite its global prevalence, data on MCTD are limited, especially in the South Asian population.  Case Report: We present the case of a 42-year-old Nepali woman with a decade-long history of myalgia, muscle weakness, and joint pain, initially misdiagnosed as rheumatoid arthritis. Over time, she developed Raynaud phenomenon, dysphagia, and progressive muscle weakness, which prompted further investigation. Serological testing revealed elevated levels of anti-U1 RNP antibodies and a positive antinuclear antibody (ANA) titer, confirming the diagnosis of MCTD according to the Alarcón-Segovia criteria. The patient was successfully managed with a regimen of corticosteroids, hydroxychloroquine, and nifedipine, resulting in significant symptomatic improvement.  Discussion: This case underscores the diagnostic challenges associated with MCTD, a condition that may present with nonspecific symptoms and mimic other rheumatic diseases. The prolonged diagnostic journey of this patient highlights the need for heightened clinical suspicion and comprehensive serological testing in patients with overlapping connective tissue disease features. Furthermore, the case contributes to the limited body of literature on MCTD in the South Asian population, emphasizing the importance of early recognition and tailored management strategies to improve patient outcomes.  Conclusion: MCTD is a complex and under-recognized autoimmune disorder, particularly in the South Asian context. This case report highlights the importance of considering MCTD in the differential diagnosis of patients with multi-systemic involvement and underscores the role of serological testing in confirming the diagnosis. Early diagnosis and appropriate management are crucial in mitigating disease progression and improving the quality of life for patients with MCTD.