Idiopathic (40 percent of cases)
Infectious causes
		Beta-hemolytic streptococci
		Yersinia species
		Hepatitis C virus
		Mycobacterium species
		Chlamydia trachomatis
		Coccidioides immitis
Noninfectious causes
	Medications
		Sulfonamides
		Oral contraceptives
Systemic lupus erythematosus
Sarcoidosis
Ulcerative colitis
Behçet's syndrome
Pregnancy