Shrinking lung syndrome: A pulmonary manifestation of systemic lupus erythematosus. Diurnal findings and nocturnal events

Objectives: To describe the diurnal and nocturnal findings of 4 adults (3 women) and one child with systemic lupus erythematosus and shrinking lung syndrome. Design: A prospective observational study. Setting: A 750 teaching-bed-hospital with a reference population of 350,000 people. Interventions: Clinical history, blood analysis, imaging test, pulmonary function tests, maximal inspiratory and expiratory pressures, arterial blood gases, and sleep studies. Measurements and Results: Patients were referred to the pneumology service for dyspnea. Two adults who showed severe arthritis in their hands had been previously diagnosed of rheumatoid arthritis. No visceral involvement was found other than lung disease. Biological results showed normal muscle enzyme values. Chest x-ray and CT scan revealed small lungs without parenchymal or pleural involvement. Pulmonary function tests indicated the presence of restrictive disease with normal carbon monoxide transfer. The alveolar-arterial gradient was within normal limits. Maximal inspiratory pressure was slightly low and maximal expiratory pressure was within normal limits. Sleep studies ruled out nocturnal hypoventilation and mild sleep-apnea syndrome was observed in 2 previous heavy snorers. During the follow-up period (10 to 46 months) none of the patients deteriorated. Conclusions: Shrinking lung syndrome affects a small proportion of patients with lupus and may also occur in children. It should be suspected in patients with lupus who present exertional dyspnea without apparent cause. The condition does not seem to affect sleep physiology, the clinical features tend towards stabilization regardless of the treatment prescribed. The origin of the syndrome seems to be a self-limited myositis of the diaphragm.