Iguratimod in Systemic Sclerosis

Inclusion Criteria: * Diagnosis of systemic sclerosis (SSc), as classified using the 2013 American College of Rheumatology/ European Union League Against Rheumatism classification of SSc. * Diffuse Cutaneous Systemic Sclerosis (dcSSc) as defined by 2001 LeRoy and Medsger Disease duration ≤ 3 years (defined as time from the first non-Raynaud phenomenon manifestation). * Agree to use effective contraception during the study period (women of childbearing age). * Smokers agreed to quit smoking during the study. * Ability to provide informed consent. Exclusion Criteria: * The following drugs have been used within one month before screening: including TNF-α inhibitors (continuous use for more than 14 days), IL-6 inhibitors, abatacept (continuous use for more than 14 days), JAK inhibitors (continuous use for more than 14 days). * Used rituximab within 3 months before screening. * SSc with tumor. * People with various lung infections, asthma or other lung diseases such as bronchiectasis. * For patients with severe heart, liver, kidney and other important organ dysfunction, the evaluation criteria are as follows: ALT or AST is greater than 2 times the upper limit of normal, or total bilirubin rises twice; CPK\>400; Renal crisis, or hypertension of various causes (≥160/100mmHg) is not controlled; Creatinine clearance rate \<30ml/min; White blood cell count\<3×109/L; Hemoglobin \<80g/L; Platelet count\<60×109/L; Heart function level III-IV; PaO2\<50mmHg in resting state; FEV1/FVC\<0.7. * In the period of acute or chronic infection (not including finger ulcer combined infection). * A history of peptic ulcer or bleeding within 6 months before screening. * People with allergies or multiple drug allergies. * People with mental illness or other reasons who cannot cooperate with treatment.