Suspected shrinking lung syndrome: a rare pulmonary manifestation of systemic lupus erythematosus-a case-based review of an underrecognized condition.

Shrinking lung syndrome (SLS) is a rare pulmonary manifestation of systemic lupus erythematosus (SLE). It is characterized by unexplained dyspnea, restrictive ventilatory defect, and diaphragmatic elevation without interstitial lung disease (ILD). A 32-year-old man with SLE presented with progressive dyspnea initially attributed to pleural and infectious processes. As systemic features evolved, SLE was confirmed. Pulmonary function tests (PFTs) showed severe restriction (forced vital capacity-FVC-28%, total lung capacity-TLC-37%), with elevated hemidiaphragm and no alternative pulmonary pathology, supporting the diagnosis of SLS. Treatment with highdose glucocorticoids, rituximab, and mycophenolate mofetil resulted in marked clinical improvement, substantial recovery of lung function (FVC 65%), and successful glucocorticoid withdrawal. A structured literature review (January 2021-March 2026) identified 19 studies reporting 37 SLS cases. Dyspnea was the predominant manifestation, frequently accompanied by pleuritic chest pain and dry cough. Restrictive ventilatory defects were consistently reported, with significantly reduced FVC, TLC, and transfer factor of the lung for carbon monoxide values. Imaging most commonly demonstrated elevated hemidiaphragm(s) and reduced lung volumes without ILD. Treatment predominantly involved glucocorticoids, often combined with steroid-sparing agents. Rituximab was frequently used as a steroid-sparing agent in severe/refractory cases and was generally associated with clinical and functional improvement. Based on the presented case and cases identified in literature, SLS remains a diagnostic challenge and should be considered in patients with SLE presenting with unexplained dyspnea and restrictive physiology. Early recognition and prompt immunosuppressive therapy may improve outcomes.