It is most commonly associated with HLA-B27, which has important features: HLA-B27 AAU can be associated with ocular inflammation alone or in association with systemic disease. HLA-B27 AAU has characteristic clinical features including male preponderance, unilateral alternating acute onset, a non-granulomatous appearance, and frequent recurrences, whereas HLA-B27 negative AAU has an equivalent male to female onset, bilateral chronic course, and more frequent granulomatous appearance. Rheumatoid arthritis is not uncommon in Asian countries as a significant association of uveitis. Noninfectious or autoimmune causes
Sympathetic ophthalmia
Behçet disease
Crohns disease
Fuchs heterochromic iridocyclitis
Granulomatosis with polyangiitis
HLA-B27 related uveitis
Spondyloarthritis (especially seen in ankylosing spondylitis)
Juvenile idiopathic arthritis
Sarcoidosis
Tubulointerstitial nephritis and uveitis syndrome

Infectious causes
Uveitis may be an immune response to fight an infection inside the eye. While representing the minority of patients with uveitis, such possible infections include:

brucellosis
herpesviruses (herpes zoster ophthalmicus - shingles of the eye)
leptospirosis
Lyme disease
presumed ocular histoplasmosis syndrome
syphilis
toxocariasis
toxoplasmic chorioretinitis
tuberculosis
Zika fever

Associated with systemic diseases
Systemic disorders that can be associated with uveitis include:
Enthesitis
Ankylosing spondylitis
Juvenile rheumatoid arthritis
psoriatic arthritis
reactive arthritis
Behçets disease
inflammatory bowel disease
Whipples disease
systemic lupus erythematosus
polyarteritis nodosa
Kawasakis disease
chronic granulomatous disease
sarcoidosis
multiple sclerosis
Vogt–Koyanagi–Harada disease

Drug related side effects
Rifabutin, a derivative of Rifampin, has been shown to cause uveitis. Several reports suggest the use of quinolones, especially Moxifloxacin, may lead to uveitis. White Dot syndromes
Occasionally, uveitis is not associated with a systemic condition: the inflammation is confined to the eye and has unknown cause.
Uridine triacetate (INN), formerly known as vistonuridine, is an orally active tri-acetylated prodrug of uridine used:

in the treatment of hereditary orotic aciduria (brand name Xuriden  ZOOR-ə-den);
to treat people following an overdose of chemotherapy drugs 5-fluorouracil (5-FU) or capecitabine regardless of the presence of symptoms, or who exhibit early-onset, severe or life-threatening toxicity affecting the cardiac or central nervous system, and/or early-onset, unusually severe adverse reactions (e.g., gastrointestinal toxicity and/or neutropenia) within 96 hours following the end of fluorouracil or capecitabine administration (brand name Vistogard).Uridine triacetate was developed, manufactured and distributed by Wellstat Therapeutics. It was granted breakthrough therapy designation by the U.S. Food and Drug Administration (FDA) and approved for use in the United States in 2015. References
External links
"Uridine triacetate". Drug Information Portal. U.S. National Library of Medicine.