Study population
Participants of our case control study were collected randomly from the electronic medical record database between October 2019 and April 2020 from Rheumatology and Rehabilitation Department, and Pediatric Department; Pulmonology, Immunology and Allergy Unit, children hospital. All experimental procedures were approved and formed in accordance with the guidelines of Institutional Review Board (IRB) of Faculty of Medicine, Zagazig University, Egypt (Approval No.: ZU-IRB #544459/14-7-2019).
Totally, the study include the connective tissue diseased children aged 5-15 years at primary diagnosis, according to the following classification criteria: the 2010 European League Against Rheumatism (EULAR) criteria for rheumatoid arthritis (RA)24 , the 2019 European League against Rheumatism (EULAR) criteria for systemic lupus erythematosus (SLE)25 , the 2017 European League against Rheumatism (EULAR) criteria for dermatomyositis (DM)26, The 2007 Pediatric Rheumatology European Society/American College of Rheumatology/European League against Rheumatism provisional classification criteria for juvenile systemic sclerosis (SSc) 27, and The 2019 Diagnostic criteria for mixed connective tissue disease (MCTD): From the Japan research committee of the ministry of health, labor, and welfare for systemic autoimmune diseases28. While we exclude patients with Active malignancy, and active acute infections.
The patients were examined for presence of ILD according to according to American Thoracic Society clinical practice guideline: classification, evaluation, and management of childhood interstitial lung disease and European protocols for the diagnosis and initial treatment of interstitial lung disease in children 29-32 . The participants were divided into four groups, Group 1 (control group) consisted of (20) healthy control volunteer children; Group 2 (CTD group): included (20) connective tissue diseased children without interstitial lung disease; Group 3 (CTD+ILD group): which consisted of (20) connective tissue diseased children with interstitial lung disease, 16 of the were already diagnosed and 4 patients were newly diagnosed at time of study. Group 3 were subdivided according to severity of interstitial lung disease (according to the pulmonary function tests) 20 as follow: Group 3a (mildILD subgroup): which consisted of connective tissue diseased children with mild interstitial lung disease. Group 3b (severeILD subgroup): which consisted of connective tissue diseased children with severe interstitial lung disease.