Interstitial lung disease and Sjögren's syndrome in primary biliary cirrhosis: a causal or casual association?

Interstitial lung disease (ILD) has been reported in patients with primary biliary cirrhosis (PBC); however, its frequency and pathogenesis are still poorly documented. Sjogren's syndrome (SS) is fairly common among patients with PBC, but the relationship between SS and PBC also remains controversial. To determine whether ILD and SS in PBC is a causal or casual association, whether SS accompanying PBC, could be considered secondary to or associated with PBC. One hundred and nine consecutive PBC cases were analyzed, and the differences of clinical features, histological stages, and serum autoantibodies between the PBC patients with and without SS were compared. There were 46 PBC patients with SS and 63 without SS, and 11 patients met the criteria of ILD. SS is associated with PBC in the form of secondary SS. The frequency of ILD in PBC patients with SS was 21.7% while only 1.6% in PBC patients without SS (P<0.0001). ILD in PBC was related to SS, with Spearman's rank coefficient of 0.330 (P=0.000). The association of SS with PBC, significantly higher in patients with than without ILD, which supports the hypothesis that ILD and SS in PBC, may be a causal, not casual, association.