Inclusion Criteria:  1. Age over 18 years and under 65. 2. Man with a diagnosis of silicosis in the form of PMF by lung or lymph node biopsy, or by radiological criteria. 3. History of exposure to silica in work with artificial stone for at least 5 years. 4. Patients capable of consenting to their participation in the study by providing written informed consent, or, if they are not trained, through a legal repressentative.  Exclusion Criteria:  1. Participation in another clinical trial in the 6 months prior to the start of participation in this study. 2. Hypersensitivity to any of the components of pirfenidone. 3. Biological or farmacological treatment for any other disease or condition related to silicosis or PMF. Exception: prednisona (or equivalent) dose 20mg per day or lower. 4. Concomitant treatment with a drug that can causes pirfenidone interactions: Cytotoxic drugs, immunosuppressants, cytokine modulators including but not limited to azathioprine, bosentan, ambrisentan, cyclophosphramide, cyclosporine, etarnecept, iloprost, infliximab, leukotriene antagonists, methotrexate, mycophenolate , tacrolimus, montelukast, tetrathiomolybdate, TNF-alpha inhibitors, imatinib mesylate, interferon gamma 1-beta, and tyrosine kinase inhibitors. Strong CYP1A2 inhibitors (eg fluvoxamine, enoxacin), P-glycoprotein or CYP3A4 inhibitors (eg Ketoconazole, erythromycin), or their inducers (eg rifampicin, carbamazepine, phenytoin). Other moderate CYP1A2 inhibitors (eg amiodarone or propafenone) which will also be prohibited. Any investigational therapy in an active clinical trial. Grapefruit juice. 5. Active infectious disease. 6. Any pathology that may condition the evolution of respiratory diseases, including cancer, HIV, HBV, HCV, liver cirrhosis, liver failure, severe kidney failure or any other that in the opinion of the investigator may interfere with the results of the study. 7. Active smoking. 8. Laboratory test abnormalities at screening timepoint - Total bilirrubin >2 ULN - AST/SGOT or ALT/SGPT > 2.5 ULN - Alkaline phosphatase >3.0 ULN - Creatinine clearance <40 mL/min (Cockcroft-Gault). 9. Concomitant treatments that may cause serious digestive events. 10. Digestive surgery or similar procedures that may cause digestive intolerances. 11. Not availability to complete all the trial visits. 12. Angiodema