Progression of idiopathic pulmonary fibrosis: lessons from asymmetrical disease.

Background: In idiopathic pulmonary fibrosis (IPF) the distribution and spatial-temporal progression of fibrotic changes may be influenced by general or locoregional conditions. From this perspective, patients with asymmetrical disease (AIPF) may be unique.
Methods: This retrospective study included 32 patients (26 men, mean ± SD age 69 ± 7 years) with AIPF, as defined by an asymmetry ratio (most affected--least affected fibrosis score)/(most affected + least affected fibrosis score) >0.2. The global fibrosis score was the average of the right and left scores. Patients with AIPF were compared with 64 matched controls with symmetrical IPF.
Results: Patients with AIPF did not differ from controls in global fibrosis score and forced vital capacity, but carbon monoxide transfer factor was less decreased (52 ± 19% vs 43 ± 13%, p=0.009). The rate of gastro-oesophageal reflux and acute exacerbations was significantly higher in patients with AIPF (62.5% vs 31.3%, p=0.006 and 46.9% vs 17.2%, p=0.004, respectively). In patients with AIPF the right side was more likely to be involved (62.5%); the median asymmetry ratio was 0.5 (range 0.24-1). Although the global fibrosis score worsened significantly in all 23 patients with AIPF with serial high-resolution CT scans (p<0.0001), pulmonary fibrosis remained asymmetrical in all except three. During follow-up, 15 patients with AIPF experienced 18 acute exacerbations. The first episode was virtually unilateral, occurring in the most affected lung in 10 patients (66.7%). Survival was similar between patients with AIPF and controls.
Conclusion: AIPF may be related to locoregional factors including gastro-oesophageal reflux which may be responsible for both disease expansion and the occurrence of acute exacerbations.