Background/Purpose: Pulmonary arterial hypertension (PAH) may be a disease manifestation of patients with anti-PM-Scl antibody (PM-Scl). In the 2014 ACR annual meeting we reported significantly higher prevalence of precapillary PAH proven by right heart catheterization (RHC) in our patients with PM-Scl compared to historical general population. This study aimed to further characterize PAH in our cohort of patients with PM-Scl.

Methods: All patients screened for PM-Scl between October 1999 and April 2014 were evaluated through our electronic medical record. PAH had to be established by RHC and patients were further subdivided into ‘PAH with interstitial lung disease (ILD)’ and ‘PAH without ILD’. The patients were defined to have ‘PAH with ILD’ if RHC confirmed pre-capillary PAH and forced vital capacity (FVC) was < 60% of predicted. High resolution CT scans (HRCT) were reviewed by a thoracic radiologist with expertise in ILD (RY), and scored to estimate severity of ILD according to the criteria defined by Ooi et al (Acta Radiologica 2003;44:258-264). Radiographic diagnoses on HRCT [cellular non-specific interstitial pneumonia (NSIP), fibrotic NSIP, usual interstitial pneumonia (UIP), and organizing pneumonia (OP)] were determined. Also, the correlation between HRCT score and mean pulmonary artery pressure (mPAP) was analyzed.

Prevalence of PAH in the general population and in patients with SSc were identified by a systematic literature review. A meta-analysis was performed to formulate prevalence of pre-capillary PAH in SSc patients both with and without ILD. Estimates of prevalence were compared using exact binomial tests.

Results: Of the 42 patients with PM-Scl, 3 patients (7.1%) had PAH with ILD and 2 patients (4.8%) had PAH without ILD.  Among the 3 patients with PAH with ILD, 2 had cellular NSIP and 1 had UIP. Due to the small sample size it was difficult to establish any significant linear correlation between mPAP and HRCT score. Systematic literature review identified 5 studies looking at prevalence of PAH in the general population, 3 evaluating PAH with ILD in SSc and 7 assessing PAH without ILD in SSc. Based on these studies the mean prevalence of PAH in the general population was 8.6/million and the maximum estimated prevalence of PAH in the general population was 13.8/million. These numbers were statistically lower than the prevalence of pre-capillary PAH in our cohort (P<0.001) and that of PAH without ILD (P<0.001). Meta-analysis revealed the estimated prevalence of pre-capillary PAH in patients with SSc was 6.3% (95%CI 4.6-8.6%), that of PAH with ILD in patients with SSc was 2.1% (95%CI 1.3-3.5%), and that of PAH without ILD in patients with SSc was 6.4% (95%CI 4.6-9.0%). In comparison to our cohort with PM-Scl no statistically significant difference was noted but there was a trend towards a higher prevalence of PAH with ILD in our cohort compared to that in SSc patients (7.1% vs 2.1%, P=0.058). 

Conclusion: Prevalence of PAH in patients with PM-Scl may be higher than that in the general population but may be comparable to the prevalence of PAH in SSc. Prevalence of PAH with ILD may be higher in patients with PM-Scl compared to that in SSc patients. In this small study, it was difficult to ascertain any correlation between ILD severity and mPAP.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/pulmonary-arterial-hypertension-in-patients-with-anti-pm-scl-antibody-2/