[Lung involvement of primary Sjögren's syndrome]

To evaluate the incidence, clinical manifestations and immunological features of lung involvement in patients of primary Sjögren's syndrome (pSS).

Five hundred twenty-two patients with pSS in Peking Union Medical College Hospital between 1985 and 2005 were screened retrospectively for lung involvement by either the abnormalities of chest imaging, lung function or the pulmonary artery systolic pressure estimated by ultrasonic echocardiogram > or = 40 mm Hg (1 mm Hg = 0.133 kPa), excluding infections, chronic obstructive pulmonary disease, asthma, congenital heart disease, rheumatic heart disease and other diseases. The difference was compared between patients with and without lung involvement. All patients fulfilled the 2002 international classification (criteria) for pSS.

(1) The incidence of lung involvement in pSS was 42.3% (221/522) and occurred from 0 to 384 months (median, 48 months) after onset, while 25.2% occurred before the diagnosis of pSS. Only 47.1% of the patients showed respiratory symptoms. The average age of onset was older in patients with lung involvement than in those without lung involvement [(43 +/- 13) yr vs (37 +/- 14) yr, t = -5.445, P = 0.000]. Incidences of dry mouth (89.6% vs 81.1%, chi2 = 7.145, P = 0.008), dry eyes (78.7% vs 66.4%, chi2 = 9.472, P = 0.002) and rampant caries (55.2% vs 42.2%, chi2 = 8.647, P = 0.003) were higher in patients with lung involvement than those without. There was no significant difference in sex ratio between the two groups. (2) Interstitial lung disease was the most common lung involvement and occurred in 23.2% of the patients. Pulmonary artery hypertension in 12.5%, multiple pulmonary bullae in 9.2%, pleural effusion in 6.0% and multiple pulmonary nodules in 5.6%. (3) The major histopathological patterns were nonspecific interstitial pneumonia (5/11 cases), lymphocytic interstitial pneumonia (3/11 cases). (4) Incidences of Ranaud' s phenomenon (26.7% vs 13.0%, chi2 = 15.77, P = 0.000 ), low-grade fever (20.4% vs 13.0%, chi2 = 5.175, P = 0.023), arthrosis (29.4% vs 21.6%, chi2 = 4.164, P = 0.041), anti-U1RNP (18.2% vs 11.2%, 2 = 5.069, P = 0.024) and hypergammaglobulinemia (51.6% vs 39.5%, chi2 = 6.597, P = 0.01) were higher in patients with lung involvement than in those without. The incidence of renal tubule acidosis was lower in patients with lung involvement than in those without (5.4% vs 12.6% chi2 = 7.616, P = 0.006). (5) The death incidence in pSS with pulmonary involvement was 5.5 times higher than in those without. The most frequent cause of death was infection (64.3%), especially pulmonary infection.

Lung involvement in pSS is common. As it is an important factor related to the prognosis of this disease, chest X-ray, HRCT, lung function and ultrasonic echocardiogram after the diagnosis are suggested.