Inflammation of the pericardium
Idiopathic (25-85%)
Infection (up to 20%)
Viral
Bacterial
TB
HIV
Malignancy
Hematologic
Lung
Breast
Primary cancers of the pericardium are rare but potential causes
Uremia
Chronic kidney failure
Post radiation
Connective tissue disease or other autoimmune conditions
Drugs:
Procainamide
Hydralazine
Methyldopa
Phenytoin
Anticoagulants (especially warfarin and heparin)
Cardiac injury (can see up to weeks later)
Post MI (Dressler's syndrome)
Thoracic trauma
Aortic dissection
Cardiac surgery
Viral
Bacterial
TB
HIV
Hematologic
Lung
Breast
Primary cancers of the pericardium are rare but potential causes
Chronic kidney failure
Procainamide
Hydralazine
Methyldopa
Phenytoin
Anticoagulants (especially warfarin and heparin)
Post MI (Dressler's syndrome)
Thoracic trauma
Aortic dissection
Cardiac surgery
Pericarditis
Cardiac
Constrictive pericarditis
ST-segment elevation myocardial infarction 
Myocarditis 
Post-MI 
Myocarditis
Previous MI with recurrent ischemia in same area