Shrinking lung syndrome: recognition, pathophysiology and therapeutic strategy

Shrinking lung syndrome is a rare complication of systemic autoimmune diseases, mainly systemic lupus erythematosus, but also Sjögren's syndrome and polymyositis. It should be suspected in any patient with autoimmune disease presenting with an unexplained dyspnea. Shrinking lung syndrome is characterized by small lung volumes, elevation of the diaphragm and restrictive physiology without parenchymal involvement. Its pathogenesis remains controversial: diaphragm dysfunction, phrenic neuropathy or pleural inflammation. Pleural adhesions and pain probably play a significant role in the pathogenesis. Electrical or magnetic phrenic stimulation is an important method of investigation but it is not widely available. No treatment has been validated. Steroids are proposed as first-line treatment, alone or associated with β2-adrenergic receptor agonists. In refractory cases, immunosuppressors are used. Biotherapies may be beneficial. Long-term prognosis is good, but respiratory failure can occur in some cases.