FRI0228 KL-6 AS A BIOMARKER OF DEVELOPING INTERSTITIAL LUNG DISEASE IN PATIENTS WITH SJÖGREN SYNDROME
Authors: Yu-Hsiang Chiu, Chun-Chi Lu, Feng-Cheng Liu, Shin-En Tang, Shi-Jye Chu, San-Yuan Kuo, Hsiang-Cheng Chen
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> Sjögren syndrome (SS) is an autoimmune disease presented with exocrine gland inflammation and extra-glandular involvement. The prevalence of pulmonary involvement, including interstitial lung disease (ILD), in patients with primary SS widely varies from 8% to 20%.<sup>1, 2</sup>Patients with SS with ILD have high morbidity and a fourfold increase in mortality.<sup>3</sup> <h3>Objectives</h3> Krebs von den Lungen-6 (KL-6) is a mucin-like, high-molecular-weight glycoprotein; it is expressed in regenerating type II pneumocytes. Serum KL-6 is highly associated with the activity of ILD in patients with radiation pneumonitis, idiopathic pulmonary fibrosis, hypersensitivity pneumonitis, sarcoidosis, rheumatoid arthritis, polymyositis, dermatomyositis and systemic sclerosis.<sup>4-8</sup> The increase in serum KL-6 level might reflect the increase in the number of regenerating type II pneumocytes secondary to pulmonary damage.<sup>8</sup> We hypothesise that an early pulmonary damage occurs before clinical or radiological evidence of ILD in patients with SS. <h3>Methods</h3> In this retrospective case-control study, patients who were diagnosed with primary SS and fulfilled the American-European Consensus Group Criteria for Sjögren's Syndrome were included. Clinical information, laboratory results on inclusion, images and pulmonary functions test results were recorded via electronic medical records review. Pulmonary radiography including chest X-ray and chest computed tomography was reviewed by a chest physician. <h3>Results</h3> Of the 39 patients with SS, 21 (53.85%) developed ILD at the end of follow-up. The follow-up period was 2.65 ± 1.88 years. The time to diagnosis of ILD was 2.72 ± 1.74 years in the ILD group. The serum KL-6 level was 1920.10 ± 1974.26 U/ml in the ILD group and 894.11 ± 788.53 U/ml in the non-ILD group (p = 0.001). The diffusing capacity of the lungs for carbon monoxide was 70.76 ± 19.63 mmHg and 91.88 ± 12.02 mmHg in the ILD group and non-ILD group, respectively (p &lt; 0.001). <h3>Conclusion</h3> Serum KL-6 level is significantly higher in patients with primary SS with developing ILD and may represent an early non-radiographic pulmonary damage. Serum KL-6 can be a valuable biomarker in predicting the development of ILD in patients with primary SS. <h3>References</h3> [1] Roca F, Dominique S, Schmidt J, et al. Interstitial lung disease in primary Sjogren's syndrome. Autoimmunity reviews. 2017; 16: 48-54. [2] Kreider M and Highland K. Pulmonary involvement in Sjogren syndrome. Seminars in respiratory and critical care medicine. 2014; 35: 255-64. [3] Palm O, Garen T, Berge Enger T, et al. Clinical pulmonary involvement in primary Sjogren's syndrome: prevalence, quality of life and mortality-a retrospective study based on registry data. Rheumatology (Oxford, England). 2013; 52: 173-9. [4] Hamada H, Kohno N, Akiyama M and Hiwada K. Monitoring of serum KL-6 antigen in a patient with radiation pneumonia. Chest. 1992; 101: 858-60. [5] Kobayashi J and Kitamura S. Serum KL-6 for the evaluation of active pneumonitis in pulmonary sarcoidosis. Chest. 1996; 109: 1276-82. [6] Oyama T, Kohno N, Yokoyama A, et al. Detection of interstitial pneumonitis in patients with rheumatoid arthritis by measuring circulating levels of KL-6, a human MUC1 mucin. Lung. 1997; 175: 379-85. [7] Takanashi S, Nishina N, Nakazawa M, Kaneko Y and Takeuchi T. Usefulness of serum Krebs von den Lungen-6 for the management of myositis-associated interstitial lung disease. Rheumatology (Oxford, England). 2019. [8] Elhai M, Hoffmann-Vold AM, Avouac J, et al. Performance of candidate serum biomarkers for systemic sclerosis-interstitial lung disease. Arthritis &amp; rheumatology (Hoboken, NJ). 2019. <h3>Disclosure of Interests</h3> None declared