Interstitial Lung Disease in Systemic Autoimmune Rheumatic Diseases: Current Approaches to Screening, Monitoring and Treatment

Interstitial lung disease (ILD) is recognized as one of the most frequent clinical manifestations of systemic autoimmune rheumatic diseases (SARDs).It is associated with increased mortality and morbidity rates among patients, making it a significantly poor prognostic factor.Although its underlying disease pathogenesis is poorly understood, it is thought to result from a complex interplay of immune dysregulation, loss of self-tolerance and chronic inflammation.Variation in disease mechanisms underlying various SARDs makes diagnosis, management and the development of targeted therapies challenging.The use of pulmonary function tests and high-resolution computed tomography scans is a cornerstone in the diagnosis and monitoring of SARD-ILD, and current therapeutic strategies are focused on the use of immunosuppressive therapies to target underlying disease pathways.However, limited evidence surrounding effective treatments for various SARD-specific ILDs highlights the need for disease-specific approaches, rather than a uniform approach to treatment options.Recommendations from the American College of Rheumatology (ACR) currently provide guidance to clinicians based on recent advancements, and the publication of UK-specific guidelines by the British Society of Rheumatology is highly anticipated.This article aims to provide an overview of the current therapeutic landscape of SARD-ILD and to discuss the current unmet needs in relation to its screening, diagnosis and monitoring.Interstitial lung disease (ILD) is recognized as one of the most frequent and potentially life-threatening pulmonary complications of systemic autoimmune rheumatic diseases (SARDs), a group of rare chronic inflammatory conditions characterized by autoimmune system dysregulation and chronic systemic inflammation.ILDs are a heterogeneous group of lung disorders that are underpinned by varying degrees of inflammation and fibrosis of the lung parenchyma. 1 Known causes of ILD include environmental and occupational exposures-related ILD, particularly hypersensitivity pneumonitis, and SARD-related ILDs, such as rheumatoid arthritis (RA), systemic sclerosis (SSc), idiopathic inflammatory myopathies (IIM), systemic lupus erythematosus (SLE) and Sjögren's syndrome (SjS).The most common ILD is idiopathic pulmonary fibrosis (IPF), which is an unknown cause of ILD, but incidence and prevalence vary in different locations, with some describing SARD-ILD as the most frequent form of ILD.1,2 The disease course of ILD is extremely variable, ranging from mild to rapidly progressive and potentially lifethreatening respiratory failure.Its presence is a significantly negative prognostic indicator, associated with increased mortality and morbidity rates among patients with SARDs. 3 It not only greatly affects patient quality of life but also poses a significant economic burden, by incurring large healthcare-related and societal-based costs.Epidemiological data show high variability in incidence and prevalence rates of SARD-ILD, as rates vary significantly depending on the underlying rheumatic disease.4 Although ILD manifests via a vast range of SARDs, there are some conditions that display particularly higher incidences, therefore necessitating careful routine baseline and follow-up assessments, such as RA, SSc and some subgroups of IIM, such as antisynthetase syndrome and overlap syndromes (e.g.polymyositis/scleroderma [PM/Scl], anti-Ku protein antibody or anti-U1 ribonucleoprotein antibodies [U1RNP]).5 ILD is less commonly associated with SLE, anti-neutrophil cytoplasmic antobody (ANCA) associated vasculitis (AAV; particularly microscopic polyangiitis), mixed connective tissue disease (MCTD) and primary SjS.