lupus can have shrinking lung syndrome

  • disease: 1.shrinking lung syndrome
  • pathophysiology: 2.unclear but myopathy, phrenic neuropathy, pleural inflammation could be cause
  • image:
    • 2.CT shows pleura thickening, elevated diaphgram, no lung parenchymal abnormality
    • 2.US shows decreased diaphragmatic excursion
  • PFT: 2.decreased TLC but normal FEV1/FVC, decreased DLCO
  • treatment: 2.steroid

This patient has a lengthy history of SLE and now presents with signs of acute inflammation and progressive dyspnea for 6 weeks with impaired PFT results, limited diaphragmatic excursion, and chest imaging demonstrating marked thickening of the lower portion of the pleura. This combination is most consistent with shrinking lung syndrome (SLS) associated with SLE. The low lung volumes noted at chest imaging are likely the origin of the condition's name, which is actually a misnomer because the lung parenchyma in these patients is typically unaffected. 

Less than 3% of patients with SLE develop SLS, with a female predominance ranging from 6:1 to 17:1. The pathophysiology is not well understood, with some evidence suggesting a component of diaphragm thinning and weakness, phrenic neuropathy, and even myopathy. However, results from larger case series demonstrate more than 75% of patients with SLS report pleuritic chest pain with pleural thickening, raising the likelihood that pleural inflammation plays a predominant role. Some proposed mechanisms suggest diaphragmatic pleural inflammation interfering with normal phrenic nerve stimulation, and this may contribute to muscle atrophy. The combination of a thickened, restrictive pleura; impaired phrenic nerve stimulation; and diaphragm atrophy all likely contribute to diaphragm weakness and limited contraction. 

There are no established diagnostic criteria, but patients with SLE and progressive dyspnea typically have a reduction in the total lung capacity, with radiographs showing elevated diaphragms and low lung volumes. This patient had these features plus impaired diaphragmatic excursion and inspiratory force, all consistent with SLS. The representative chest CT scan demonstrates almost no lung parenchymal disease, pointing away from SLE pneumonitis. Although SLE can be associated with a variety of central and peripheral neuropathic entities, including mononeuritis, the presence of a thickened pleura suggests there is more contributing to the breathing impairment. A previous empyema with residual fibrous peel could explain the radiographs; however, her diaphragm excursion is impaired bilaterally, which would be unusual for a past empyema.

Currently, there are no evidence-based treatment guidelines for SLS, but results from case reports and series have suggested corticosteroids dosed at ranges from prednisone (30 mg/day) or even pulse dose methylprednisolone (1 g/day) produce a good response. This patient also had active nephritis, was treated with pulse dose methylprednisolone, and had significant improvement in her symptoms and PFT results within 3 weeks. There are reports of improvement with rituximab, but other therapies, including methotrexate, cyclophosphamide, and mycophenolate mofetil, have not been shown to be effective. 1

Footnotes

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