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Clinical History

A 48-year-old female, on irregular follow-up for systemic lupus erythematosus (SLE), came to the pulmonary medicine outpatient department with a 2-year history of easy fatiguability and exertional dyspnea progressing to current dyspnea at rest. She had no history of orthopnea or paroxysmal nocturnal dyspnea.

Imaging Findings

Chest X-Ray (CXR) in posteroanterior view revealed an elevated right hemidiaphragm with reduced lung volume on the right. No obvious lung parenchymal, cardiac, and mediastinal abnormalities were noted.

On further evaluation with high-resolution computed tomography (HRCT) of the chest, conclusive evidence of an elevated right hemidiaphragm and significant volume loss in the right middle and lower lobes with subsegmental atelectasis were seen. No features of parenchymal/pleural/vascular disease were noted. 

Additionally, an M mode ultrasound of the chest was performed, demonstrating a paradoxical movement of the right hemidiaphragm on inspiration.

Discussion

Shrinking Lung Syndrome (SLS) is a rare diagnosis of exclusion, usually occurring in female patients, after a mean duration of 4-6.5 years from the diagnosis of SLE.[1,2] It was first described by Hoffman and Beck in 1965 and is characterized by unexplained dyspnea and a decrease in lung volume, with or without a hemidiaphragm elevation, in the absence of implicit alveolar or interstitial disease. [3] Currently, a combination of pathophysiological mechanisms including pleural inflammation and chronic hypoventilation due to SLE-associated neuro-myopathy have been attributed to SLS. [4–6]

As with our case, SLS often presents as exertional dyspnea progressing over months (98.87%) [2,7] and pleuritic chest pain (76%).[2] It may also rarely present as fever (19%) or dry cough (8%).[2]  Features of SLS occur independently of the course, severity, and biomarkers of SLE and are non-collateral with features of other major organ involvement.[8] Examination usually reveals tachypnea with the use of accessory respiratory muscles and bilateral shrinking of lung borders without characteristic auscultatory findings apart from rare basal crepitations.[9] Sequential pulmonary function testing shows gradually decreasing lung volumes in a restrictive pattern.[2]

The moderately slow progression of SLS not only increases its morbidity but also contributes to a delay in diagnosis, (11 +/- 20 months) leading to possible drastic complications including respiratory arrest.[2,10] Findings of an elevated hemidiaphragm on Chest X-ray and/or CT findings of diaphragmatic elevation, pleuritis +/- basal laminar atelectasis without features of interstitial pneumonitis in a female patient with chronic SLE, should prompt a radiologist to report a possible diagnosis of SLS.[4,7,11,12] Additional evidence of paradoxical diaphragmatic movement can also be confirmed on M-mode ultrasonography.[13]

In our case report, a middle-aged female patient, presented with gradual onset, progressive dyspnea for the past 2 years, 8 years after a diagnosis of SLE. Her pulmonary function tests showed a restrictive pattern. CXR revealed an elevated right hemidiaphragm with reduced lung volume on the right when compared to a previous CXR performed 2 years before her presentation. The finding was further confirmed on CT, along with establishing evidence of significant volume loss in the right middle and lower lobes with subsegmental atelectasis without features suggestive of pulmonary/pleural/vascular disease. M mode ultrasound also demonstrated paradoxical movement, clinching the diagnosis of shrinking lung syndrome.

Fortunately, despite the scarcity of clinical trials, available literature on isolated cases shows a near-complete resolution of clinical and pulmonary function test results with moderate to high-dose corticosteroids in the range of 0.5-1.0mg/kg/day.[9] The addition of immunosuppressants such as Methotrexate, Rituximab, and Colchicine not only improves imaging parameters but also prevents the recurrence of SLS features while tapering corticosteroids. [9,14–16]

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