Idiopathic (nonspecific, probably viral)
Infectious causes
	Viruses: coxsackievirus A and B, hepatitis viruses, human immunodeficiency virus, measles virus, mumps virus, varicella virus
	Bacteria: gram-positive and gram-negative organisms; rarely, Mycobacterium species (tuberculosis)
	Fungi (most often in immunocompromised patients): Blastomyces dermatitidis, Candida species, Histoplasma capsulatum
Noninfectious causes
	Acute myocardial infarction*
	Renal failure†
	Malignancy: breast cancer, lung cancer, Hodgkin's disease, leukemia, lymphoma by local invasion
	Radiation therapy (usually for breast or lung cancer)
	Autoimmune disorders: mixed connective tissue disorder, hypothyroidism, inflammatory bowel disease, rheumatoid arthritis, systemic lupus erythematosus, Wegener's granulomatosis, Takayasu's arteritis6
	Trauma (including surgery): closed procedures and pacemaker implantation (puncture of myocardium)
	Drugs‡: hydralazine (Apresoline), procainamide (Pronestyl), phenytoin (Dilantin), isoniazid (e.g., Nydrazid); with rifampin (Rifamate), phenylbutazone, dantrolene (Dantrium), doxorubicin (Adriamycin, Rubex), methysergide (Sansert), penicillin, mesalamine (Rowasa)7