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Shrinking Lung Syndrome — SCE Rheumatology MCQ

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HardSLE & Antiphospholipid SyndromeShrinking Lung SyndromeSCE Rheumatology

A 25-year-old woman with systemic lupus erythematosus reports 4 months of pleuritic lower-chest pain and progressive exertional dyspnoea. Her BMI is 23 kg/m² and haemoglobin is 126 g/L. Serial chest radiographs show decreasing lung volumes with bilateral elevation of the hemidiaphragms. Pulmonary function tests show an FEV1/FVC ratio of 0.84, total lung capacity 56% predicted, FVC 54% predicted, DLCO 58% predicted and KCO 102% predicted. High-resolution CT shows no interstitial or significant pleural disease, CT pulmonary angiography shows no thromboembolism, and echocardiography shows no evidence of pulmonary hypertension. Diaphragmatic excursion is reduced, but bilateral phrenic nerve conduction is normal. What is the most likely diagnosis?

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Correct answer: E — Shrinking lung syndrome

The diagnosis is **shrinking lung syndrome**, a rare manifestation of SLE. The discriminating pattern is progressive dyspnoea with falling lung volumes, bilateral diaphragmatic elevation and an extrapulmonary restrictive defect. DLCO is reduced because alveolar volume is low, whereas preserved KCO indicates relatively intact gas transfer per unit lung volume. Significant parenchymal, pleural and vascular disease has been excluded. Bilateral phrenic neuropathy can cause diaphragmatic elevation but is less likely with normal phrenic conduction and the characteristic SLE-associated syndrome. Pulmonary arterial hypertension and chronic thromboembolic disease generally reduce DLCO without producing this marked restrictive, low-volume radiographic pattern; both are also excluded by the investigations. Acute lupus pneumonitis would cause acute systemic illness and pulmonary infiltrates rather than clear, progressively shrinking lungs.

Reference: Duron L et al. Shrinking lung syndrome associated with systemic lupus erythematosus: a multicenter collaborative study of 15 new cases and a review of the 155 cases in the literature focusing on treatment response and long-term outcomes. Autoimmunity Reviews. 2016;15:994–1000. https://pubmed.ncbi.nlm.nih.gov/27481038/