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Introduction
Idiopathic pulmonary fibrosis (IPF) is a chronic fibrosing interstitial pneumonia of unknown cause limited to the lungs and associated with the histological appearance of usual interstitial pneumonia (UIP). In the absence of surgical lung biopsy, a typical high-resolution CT (HRCT) scan is required for a definite diagnosis of IPF. According to the ATS/ERS consensus classification of idiopathic interstitial pneumonias, a typical HRCT picture consists of 'bilateral, predominantly basal and peripheral reticular pattern with minimal ground glass opacities', but there is no mention of the symmetry of abnormalities. 1 To date, the clinical course of IPF is unclear but there are shreds of evidence suggesting that it may be less of a gradual decline and more of a step-like process, with periods of relative steadiness punctuated by episodes of acute exacerbations (AE)-that is, acute respiratory decompensations with no identifiable cause. 2 These events may result in the majority of deaths related to IPF. 2
In IPF the distribution of fibrotic changes between the two lungs and their spatial-temporal progression are unknown. These may be influenced by various general or locoregional conditions which could be shared by a gradual decline and AE or be independent of each other. From this perspective, patients presenting with asymmetrical IPF (AIPF) are intriguing and offer a unique opportunity to understand better the pathogenesis and natural history of IPF. First, in this context, an aetiological factor may exert its profibrotic or antifibrotic effect with partiality for one of the lungs. Second, patients with AIPF may have a distinctive clinical/functional/radiological presentation or a particular disease course because one lung is relatively preserved.
We report a case-control study of patients with AIPF. The objectives of the study were to describe patients with AIPF in terms of (1) clinical characteristics with a focused interest on gastro-oesophageal reflux (GER), (2) radiological and functional features, (3) outcome, including HRCT progression and AE episodes and (4) mortality, and to compare them with patients with symmetrical IPF.
Methods
Patients
This retrospective study was conducted in two centres, Avicenne Hospital and Louis Pradel Hospital. It received institutional review board approval and the requirement for informed consent was waived. Clinicians of the two participating centres were asked to report their cases with an a priori AIPF. Patients' medical records were...