Rheumatoid arthritis-associated ILD

Rheumatoid arthritis (RA)-associated interstitial lung disease (ILD) is a largely under-diagnosed, serious manifestation of RA which accounts for a high mortality rate in affected patients. In recent years, more insight has been obtained regarding triggers, risk factors, and underlying mechanisms enabling more effective treatment of the condition.

Dr Phuong Phuong Diep (Oslo University Hospital, Norway) explained that data on the prevalence of ILD in RA (RA-ILD) widely vary – partly attributable to underdiagnosis. The lifetime risk of developing RA-ILD for RA patients is 3.6% and it appears that the MUC5B promoter variant is a strong risk factor. Patients with RA harbouring MUC5B have an increased lifetime risk of developing ILD of 16.8% (95% CI 13.1–20.2) versus 6.1% (95% CI 5.0–7.2) for those without MUC5B. The difference between these risks starts to become evident when patients reach the age of 65 years, with men being more at risk than women [1]. Based on high-resolution computed tomography (HRCT) findings in 1,138 patients from 12 studies, several subtypes of RA-ILD can be distinguished. These include: usual interstitial pneumonia (UIP; affecting 43% of RA-ILD patients), non-specific interstitial pneumonia (NSIP; affecting 17%), organising pneumonia (occurring in 2%), and other (seen in 6% of RA-ILD patients) [2]. Based on 7 histopathological studies (n=161), the proportion of affected patients shows a considerable variability: UIP 35%, NSIP 34%, organising pneumonia 18%, diffuse alveolar damage 2%, and unclassifiable disease 3% [3]. Patients with RA-ILD have a significantly higher morbidity and mortality compared with RA patients without ILD [4]. Based on radiological patterns, Yunt et al. showed that patients with definite or possible UIP usually have worse survival rates compared with patients with NSIP [5]. This study comprised 158 patients of whom 63% had definite UIP, 15% had possible UIP, and 22% had NSIP [5]. No survival difference was seen between patients with definite and possible UIP [5]. Dr Diep mentioned the risk factors for progressive pulmonary fibrosis (including related mortality): i.e. older age, male sex, honeycombing or UIP pattern on HRCT, reduced forced vital capacity, and reduced diffusing capacity [6,7].

1. Palomäki A, et al. Ann Rheum Dis. 2021 Dec;80(12):1530-1536.
2. Bendstrup E, et al. J Clin Med. 2019 Nov 21;8(12):2038.
3. Kim E, et al. 2009 Nov;136(5):1397-1405.
4. Hyldgaard C, et al. Ann Rheum Dis. 2017 Oct;76(10):1700-1706.
5. Yunt ZX, et al. Respir Med. 2017 May;126:100-104.
6. Wijsenbeek M, et al. N Engl J Med. 2020 Sep 3;383(10):958-968 2020.
7. Diep PP. Disease characteristics and risk of progression and mortality in rheumatoid arthritis-associated ILD. Nordic Lung Congress 2022, 01–03 Jun, Copenhagen, Denmark.

 

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Posted on 17 August, 202216 August, 2022