Fibrinous pericarditis is an inflammation of the pericardium, the protective sac surrounding the heart. This condition is characterized by the deposition of fibrin, a protein involved in blood clotting, on the pericardial surfaces. It can result from various causes, including infections, autoimmune diseases, or following a heart attack. Symptoms of fibrinous pericarditis may include chest pain, which often worsens with deep breathing or lying down. Diagnosis typically involves imaging tests like echocardiography and may show thickening of the pericardium. Treatment often includes anti-inflammatory medications to reduce pain and inflammation.