Common Links Among Patients With Pulmonary Fibrosis?
By Navneet Singh, MD
I read with interest the article by Fischer and colleagues (October 2006),wherein they describe the characteristics of systemic sclerosis (SSc)-associated interstitial lung disease in patients who presented with an initial diagnosis of idiopathic interstitial pneumonia. Symptomatic gastroesophageal reflux (GER) was one of the clinical features that was identified by the authors as being indicative of the presence of SSc-associated interstitial lung disease.
However, GER is very common among patients with idiopathic pulmonary fibrosis (IPF), the most commonly encountered idiopathic interstitial pneumonia. Raghu and colleagues2 recently demonstrated with the use of 24-h pH monitoring and esophageal manometry that GER was present in majority (87%) of patients with IPF, almost half of whom were symptomatic. Furthermore, the same group3 reported stabilization and even improvement in pulmonary function test results over a period of 2 to 6 years in a small series of patients with IPF who were treated with anti-GER medications alone. Similarly, the presence of autoimmunity in IPF is well known and was highlighted in a review.4 Anti-nuclear antibodies (ANAs) are demonstrable in serum in as many as 10 to 20% of patients with IPF.
Presence of anti-topoisomerase antibodies (that produce a nucleolar pattern on immunofluorescence testing) among patients with IPF has also been reported. The authors of the current study1 had, in fact, recently demonstrated by means of a retrospective analysis that ANA positivity (with a nucleolar staining pattern) occurred in 25 patients with IPF (8.8%), more than half of whom also had presence of anti-Th/To antibodies.
The small number of patients with ANA positivity, absence of cutaneous features of SSc in all the patients, and lack of differences (in clinical features, pulmonary physiologic-cum-gas exchange parameters and survival) between patients with ANA positivity and those without, as well as between patients with anti-Th/To antibody positivity and those without makes it difficult to substantiate the authors’ conclusions of attributing the pulmonary fibrosis as being related to SSc.
The fact is that pulmonary fibrosis (occurring in the setting of both IPF and SSc) is commonly associated with the presence of GER as well as autoimmunity, and differentiating idiopathic from nonidiopathic entities often remains a challenging issue for treating clinicians.