Shrinking Lung Syndrome in Adolescent Systemic Lupus Erythematosus: Diagnostic Utility of Diaphragmatic Ultrasound

Shrinking lung syndrome (SLS) is a rare pulmonary complication of systemic lupus erythematosus (SLE), characterized by dyspnoea, reduced lung volumes, and elevated diaphragms without significant parenchymal lung disease. We report a 17-year-old female with SLE presenting with progressive dyspnoea, dry cough, and pleuritic chest pain. Pulmonary function tests showed a restrictive defect (forced vital capacity 39% predicted) with preserved diffusing capacity. High-resolution computed tomography demonstrated reduced lung volumes with bilateral diaphragmatic elevation and basal atelectasis, without interstitial lung disease. Diaphragmatic ultrasound revealed reduced excursion and decreased thickening fraction, indicating diaphragmatic dysfunction. Alternative cardiopulmonary and neuromuscular causes were excluded, establishing the diagnosis of SLS. The patient was treated with corticosteroids and theophylline, resulting in symptomatic improvement. This case highlights the importance of recognizing SLS and demonstrates the diagnostic value of diaphragmatic ultrasound as a non-invasive tool facilitating early diagnosis and management.