Improved Lung Function With Cyclophosphamide and Rituximab in a Case of Shrinking Lung Syndrome.

Shrinking lung syndrome (SLS) is a rare respiratory complication of systemic autoimmune diseases. It is most commonly associated with systemic lupus erythematosus (SLE), often presenting as a diagnostic challenge. It is characterized by hallmark clinical features of dyspnea and pleuritic chest pain, along with radiographic evidence of reduced lung volumes and restrictive lung physiology in the absence of interstitial lung disease. Patients often demonstrate positive antibody serology due to associated underlying autoimmune conditions. In particular, anti-nuclear antibodies (ANA), low complement levels, and, in certain instances, extractable nuclear antigens (ENA) tend to be positive. We present a case of a young lady in her 20s who developed exertional shortness of breath, pleuritic chest pain, and reduced exercise tolerance. In the context of a positive autoimmune profile suggestive of SLE, typical radiological features, and pulmonary function tests, she was diagnosed with shrinking lung syndrome (SLS). The case describes therapeutic strategies that exist for the treatment of SLS, which can bring about meaningful recovery in lung function. The overall prognosis of SLS is variable, but outcomes may be favorable with timely recognition and appropriate treatment.