Shrinking Lung Syndrome: A Rare Pulmonary Complication of Systemic Lupus Erythematosus.

Shrinking lung syndrome (SLS) is a rare pulmonary complication primarily associated with autoimmune diseases such as systemic lupus erythematosus (SLE). A 38-year-old female recently diagnosed with SLE on hydroxychloroquine, prednisone, and methotrexate presented with a one-week history of progressive shortness of breath, non-productive cough, and pleuritic chest pain. She was afebrile with adequate oxygen saturation. Examination revealed a few fine crackles in the lung fields. Laboratory results showed pancytopenia. Initial treatment included broad-spectrum antibiotics and intravenous methylprednisolone for a suspected lupus flare. Cultures and tests for infections, including tuberculosis, were negative. Imaging revealed bilateral airspace disease with no pulmonary embolism. Autoimmune workup showed high antinuclear antibodies, positive anticardiolipin antibody, ribonucleoprotein, and anti-Smith antibody. Diagnosed with SLS, she was started on a tapering dose of methylprednisolone and hydroxychloroquine, along with rituximab, leading to significant improvement. Pulmonary function tests (PFTs) showed a restrictive pattern. SLS, with a very low prevalence in SLE, can also occur in systemic sclerosis, Sjogren's syndrome, and rheumatoid arthritis. Typical symptoms include dyspnea, pleuritic chest pain, and cough. Diagnosis involves chest radiography showing an elevated diaphragm and restrictive PFT pattern. Treatment often includes corticosteroids such as methylprednisolone and immunosuppressive agents. Rituximab has shown improvement in cases unresponsive to conventional therapy.