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Postgraduate Institute of Medical Education and Research, Chandigarh, India
Correspondence to: Navneet Singh, MD, Department of Pulmonary Medicine, Postgraduate Institute of Medical Education and Research, Sector 12, Chandigarh 160012, India; e-mail: navneetchd{at}yahoo.com
To the Editor:
I read with interest the article by Fischer and colleagues (October 2006),1 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 authors1 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.5 Presence of anti-topoisomerase antibodies (that produce a nucleolar pattern on immunofluorescence testing) among patients with IPF has also been reported.6 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.7 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.
Footnotes
The author has no conflicts of interest to disclose.
The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.
References
National Jewish Medical and Research Center, Denver, CO University of Pittsburgh, Pittsburgh, PA University of Colorado, Denver, CO
Correspondence to: Aryeh Fischer, MD, National Jewish Medical and Research Center, Rheumatology/Medicine, 1400 Jackson St, Denver, CO 80206; e-mail: fischera{at}njc.org
To the Editor:
We appreciate Dr. Singh’s interest in our article.1 We agree that it can sometimes be challenging to differentiate nonidiopathic forms of interstitial lung disease (ILD) from idiopathic forms. It was in this light that we identified the unique features of systemic sclerosis sine scleroderma (ssSSc)-ILD in patients who otherwise would have been categorized as having idiopathic pulmonary fibrosis (IPF).
As stated in our article, the diagnosis of ssSSc was made only if the patient had at least three or more manifestations that were typical of systemic sclerosis (SSc). We chose these manifestations based on the proposed diagnostic criteria for ssSSc.2
Consequently, a patient with ILD, gastroesophageal reflux disease, and a positive test result for antinuclear antibodies (ANAs) would not have been considered to have ssSSc. ANA positivity can occur in IPF patients, and thus we did not solely rely on this in our analysis. Rather, we highlighted the specificity of nucleolar staining for ANAs.3 In fact, in our previously described cohort of IPF subjects who were anti-Th/To-positive, we argued that, on retrospective analysis, those with ANAs revealed by nucleolar staining, and particularly those with Th/To antibodies, appeared to have had ssSSc-ILD.4
Dr. Singh states that antitopoisomerase antibodies have been reported in patients with IPF and suggests this could produce a nucleolar staining ANA. A closer review of the referenced article shows that 18 of 41 IPF patients (44%) had antibodies to DNA topoisomerase II.5 However, only 3 of the 18 patients had a positive ANA finding obtained by Hep2 cell substrate, and the pattern of immunofluorescence was not reported. Furthermore, to our knowledge, the presence of antitopoisomerase II antibodies in IPF patients has not been confirmed by another group, although it has been reported in Japanese patients with SSc-ILD.6 Additionally, antitopoisomerase II antibodies should not be confused with antitopoisomerase I (anti-Scl-70) antibodies, which are highly specific for diffuse SSc and give a nucleolar pattern on ANA testing. Notably in our study, while all six patients had ANAs revealed by nucleolar staining, only one patient showed antitopoisomerase I (anti-Scl-70) antibodies. We believe that our case definition for ssSSc-ILD accurately differentiates those patients with ssSSc from those with IPF, and that this distinction is clinically useful.
References
autoantibodies in Japanese patients with systemic sclerosis. Arch Dermatol Res 2005;297,180-183[CrossRef][ISI][Medline]Related Article
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