An Unusual Case of Primary Sjögren's Syndrome and Lymphangioleiomyomatosis Diagnosed From Refractory Cough.

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disorder that can involve the lungs, leading to interstitial lung disease (ILD) and lymphoproliferative disorders. Lymphangioleiomyomatosis (LAM) is a rare neoplastic disorder in ILD. Co-occurrence of these diseases is exceptionally rare. We report the case of a 47-year-old woman who presented with a persistent cough, initially misdiagnosed as a nonspecific respiratory condition. Empirical therapy proved ineffective. As her cough worsened and was accompanied by xerostomia and xerophthalmia, a comprehensive examination prompted a diagnosis of pSS. Although glucocorticoids and immunomodulatory therapy alleviated her sicca symptoms, the cough persisted. High-resolution computed tomography revealed cystic cavities, which were initially mistaken for bullous emphysema. The refractory cough prompted further investigation, and lung biopsy and elevated serum vascular endothelial growth factor-D confirmed LAM. Sirolimus significantly ameliorated the cough severity, while corticosteroid combined with immunosuppressive agents was continued for pSS management. Follow-up found that the patient's symptoms remained stable. This rare case underscores the diagnostic challenges of overlapping rare diseases and highlights the critical role of multidisciplinary assessment, pulmonary imaging, and histopathological examination in achieving an accurate diagnosis.