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Shrinking Lung Syndrome — RACP Adult Medicine MCQ

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HardGeneral Internal MedicineShrinking Lung SyndromeRACP Adult Medicine

A 42-year-old woman with recently diagnosed SLE develops shortness of breath. CT pulmonary angiography is negative for PE. Her lung volumes are small on CXR with elevated hemidiaphragms bilaterally. PFTs show a restrictive pattern with preserved DLCO corrected for volume. What is the most likely diagnosis?

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Correct answer: A — Pulmonary hypertension

Shrinking lung syndrome (SLS) is an uncommon but recognised pulmonary complication of SLE characterised by progressive dyspnoea, small lung volumes (elevated hemidiaphragms on CXR), and restrictive PFTs WITHOUT significant parenchymal disease. The preserved DLCO corrected for alveolar volume distinguishes it from ILD. The pathogenesis is uncertain – diaphragmatic dysfunction from phrenic nerve or diaphragmatic myopathy is hypothesised. Treatment includes corticosteroids, rituximab, or other immunosuppression. Response is variable.

Reference: eTG – 2025 – Rheumatology; Toya & Tzelepis – 2009 – Shrinking Lung Syndrome Review