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Shrinking Lung Syndrome — SCE Rheumatology MCQ

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HardSLE & Antiphospholipid SyndromeShrinking Lung SyndromeSCE Rheumatology

A 42-year-old woman with systemic lupus erythematosus develops progressive exertional dyspnoea following recurrent episodes of pleuritic chest pain. Chest radiography shows bilateral elevation of the hemidiaphragms. High-resolution CT excludes interstitial lung disease, pleural effusion and pulmonary embolism. Pulmonary function testing shows a severe restrictive defect with reduced total lung capacity; DLCO is reduced in proportion to alveolar volume, with preserved KCO. Diaphragmatic ultrasonography shows reduced excursion, but bilateral phrenic nerve conduction is normal. Which proposed pathophysiological mechanism best explains this presentation?

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Correct answer: E — Pleuritis-related inhibition of deep inspiration and diaphragmatic activation, followed by low-volume remodelling and reduced lung compliance

Explanation lettering: C = shown as B · B = shown as C · E = shown as D · D = shown as E

D is correct. Shrinking lung syndrome produces extraparenchymal restriction with low lung volumes, elevated diaphragms and no demonstrable interstitial disease. Its pathogenesis is not completely settled, but physiological evidence supports pleuritis-related reflex inhibition of deep inspiration and diaphragmatic activation. Persistent low-volume breathing may then produce remodelling and markedly reduced lung compliance. Normal phrenic conduction argues against fixed phrenic neuropathy, and primary diaphragmatic myopathy is not found in most carefully studied patients. A pleural effusion and pneumothorax would be visible on imaging. Interstitial fibrosis would produce parenchymal CT abnormalities and disproportionate impairment of gas transfer. Chronic thromboembolic disease causes pulmonary vascular limitation rather than this characteristic restrictive, elevated-diaphragm phenotype.

Reference: Henderson LA et al. Shrinking lung syndrome as a manifestation of pleuritis: a new model based on pulmonary physiological studies. Journal of Rheumatology. 2013;40:273-281. https://pubmed.ncbi.nlm.nih.gov/2602542/