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PubMed This is a summary of 19 peer-reviewed journal articles Updated
Ophthalmology

The Biology of Uveitis and Finding the Cause

At a Glance

Uveitis is an inflammation of the eye caused by an imbalance in the immune system. Finding the exact cause—whether it is an infection like herpes or an autoimmune condition like HLA-B27—is critical because treating an infection with steroids can cause severe, permanent vision damage.

Understanding why your eye is inflamed requires looking deep into the biology of the immune system. Your eye is normally a “protected” site, meaning the body has barriers to keep most immune cells out. In uveitis, those barriers break down, and the immune system begins to attack the eye’s own tissues [1][2].

The Biological Mechanism

At the heart of uveitis is an imbalance in your T-cells, which are the “scouts” of your immune system [3].

  • Inflammatory Cells: Specific inflammatory immune cells become overactive and release chemicals that cause swelling and tissue damage [4][5].
  • Regulatory T-cells (Tregs): These are “peacekeeping” cells that normally calm inflammation. In uveitis, there are often not enough Tregs, or they aren’t working correctly to stop the attack [3][6].
  • Blood-Retinal Barrier (BRB) Breakdown: Normally, a tight barrier of cells protects the retina. When inflammation occurs, this barrier becomes “leaky,” allowing more inflammatory cells to flood into the eye, which can lead to vision-threatening swelling [2][5].

Why the Cause Matters

Before starting treatment (see Standard of Care: The Treatment Step-Ladder), your doctor must determine if the inflammation is caused by an infection or an autoimmune reaction. This is critical because the treatment for one could worsen the other [7][8].

Infectious Causes

If an infection is present, the immune system is trying to fight off an invader. Common infectious causes include:

  • Viruses: Herpes Simplex (HSV), Shingles (VZV), or Cytomegalovirus (CMV) [9].
  • Bacteria: Syphilis or Tuberculosis (TB) [7].
  • Parasites: Toxoplasmosis, often from contact with cat litter or undercooked meat [10].

Non-Infectious (Autoimmune) Causes

In these cases, the immune system mistakenly attacks the eye. This is often linked to genetic markers or systemic diseases:

  • HLA-B27: A genetic marker associated with Ankylosing Spondylitis (back spine inflammation) [11].
  • Sarcoidosis: An inflammatory disease that can affect the lungs and skin [12].
  • Behçet’s Disease: A condition involving mouth/genital sores and skin rashes [11].
  • VKH (Vogt-Koyanagi-Harada): An autoimmune disorder that affects the eyes, ears, and nervous system [13].

The Danger of “Masquerade Syndromes”

Some conditions are not uveitis at all but “masquerade” as inflammation. The most serious is Intraocular Lymphoma, a type of cancer that can look identical to uveitis in a standard eye exam [14][15].

A “masquerade” is often suspected if the “uveitis” does not respond to treatment or if it gets better with steroids but returns the moment the dose is lowered [15][16]. Because steroids can temporarily shrink lymphoma cells, they can “hide” the cancer and delay a life-saving diagnosis [15][17].

Why Steroids Require Caution

Corticosteroids (steroids) are the gold standard for calming autoimmune inflammation. However, if they are used on an undiagnosed infection, they can act like “fuel on a fire” by suppressing the immune system’s ability to fight the invader [10][18]. For example, giving steroids to someone with untreated Toxoplasmosis or Fungal infections can lead to rapid and permanent vision loss [10][19]. This is why your doctor may wait for blood test results before starting intensive treatment.

Common questions in this guide

Why does my eye doctor need to run blood tests before treating my uveitis?
Blood tests help determine if your uveitis is caused by an underlying infection or an autoimmune disease. This is crucial because using steroids to treat autoimmune inflammation can rapidly worsen an undiagnosed infection.
What is a masquerade syndrome in uveitis?
A masquerade syndrome occurs when a serious condition, like intraocular lymphoma, mimics the symptoms of uveitis. Doctors suspect this if the inflammation doesn't respond to standard treatments or worsens when steroid doses are lowered.
Can back pain or joint stiffness be related to my uveitis?
Yes, recurrent uveitis is often linked to an autoimmune genetic marker called HLA-B27. This marker is strongly associated with systemic inflammatory conditions like ankylosing spondylitis, which causes lower back and joint pain.
What role do T-cells play in eye inflammation?
T-cells act as scouts for your immune system. In uveitis, an imbalance occurs where inflammatory T-cells become overactive and regulatory T-cells fail to calm the inflammation, leading to swelling and tissue damage in the eye.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What specific tests (like blood work or a sample of eye fluid) have you run to rule out infections like Syphilis, TB, or Herpes?
  2. 2.Am I at risk for a 'masquerade syndrome,' and what signs would suggest we need to look for something like lymphoma?
  3. 3.Why is it important for me to wait for certain test results before we start high-dose steroids?
  4. 4.If I have a positive HLA-B27 test, what other symptoms in my body (like joint pain or back stiffness) should I tell you about?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (19)
  1. 1

    Targeted Medical History and Diagnostic Testing in Uveitis.

    Grajewski RS, Tappeiner C, Thurau S

    Klinische Monatsblatter fur Augenheilkunde 2022; (239(5)):654-658 doi:10.1055/a-1737-4306.

    PMID: 35320872
  2. 2

    Mechanisms of blood-retinal barrier disruption related to intraocular inflammation and malignancy.

    Tomkins-Netzer O, Niederer R, Greenwood J, et al.

    Progress in retinal and eye research 2024; (99()):101245 doi:10.1016/j.preteyeres.2024.101245.

    PMID: 38242492
  3. 3

    Th17 Activation and Th17/Treg Imbalance in Prolonged Anterior Intraocular Inflammation after Ocular Alkali Burn.

    Yuan M, Qian X, Huang Y, et al.

    International journal of molecular sciences 2022; (23(13)) doi:10.3390/ijms23137075.

    PMID: 35806082
  4. 4

    The DNA Methylation Inhibitor Zebularine Controls CD4+ T Cell Mediated Intraocular Inflammation.

    Zou Y, Hu X, Schewitz-Bowers LP, et al.

    Frontiers in immunology 2019; (10()):1950 doi:10.3389/fimmu.2019.01950.

    PMID: 31475011
  5. 5

    Activation of the interleukin-23/interleukin-17 signalling pathway in autoinflammatory and autoimmune uveitis.

    Zhong Z, Su G, Kijlstra A, Yang P

    Progress in retinal and eye research 2021; (80()):100866 doi:10.1016/j.preteyeres.2020.100866.

    PMID: 32422390
  6. 6

    Metabolic checkpoints in the regulation of Th17 cells: implications for uveitis pathogenesis and therapy.

    Ma Y, Zhang Q, Ding Z

    Frontiers in immunology 2026; (17()):1690141 doi:10.3389/fimmu.2026.1690141.

    PMID: 41743733
  7. 7

    Immunological tests and their interpretation in uveitis.

    Rathinam SR, Tugal-Tutkun I, Agarwal M, et al.

    Indian journal of ophthalmology 2020; (68(9)):1737-1748 doi:10.4103/ijo.IJO_570_20.

    PMID: 32823389
  8. 8

    Treatment of severe non-infectious uveitis in high-risk conditions (Part 2): systemic infections; management and safety issues.

    Cordero-Coma M, Salazar-Méndez R, Yilmaz T

    Expert opinion on drug safety 2015; (14(9)):1353-71 doi:10.1517/14740338.2015.1061992.

    PMID: 26118392
  9. 9

    Varicella zoster virus cerebral aneurysmal vasculopathy presenting in a newly-diagnosed HIV-positive patient.

    Tomkins A, Babu C, Herwadkar A, et al.

    International journal of STD & AIDS 2018; (29(13)):1351-1353 doi:10.1177/0956462418786334.

    PMID: 30049255
  10. 10

    The Role of Corticosteroids in Treating Acute Ocular Toxoplasmosis in an Immunocompetent Patient: A Case Report.

    Lin HY, Lee WA

    Frontiers in medicine 2022; (9()):843050 doi:10.3389/fmed.2022.843050.

    PMID: 35847774
  11. 11

    The epidemiology of uveitis: comparison of its causes and visual outcomes between three-tiered medical facilities in Ube city.

    Yanai R, Uchi SH, Kondo Y, et al.

    Scientific reports 2025; (15(1)):8998 doi:10.1038/s41598-025-93223-x.

    PMID: 40089526
  12. 12

    Serial Frequencies and Clinical Features of Uveitis in Hokkaido, Japan.

    Iwata D, Mizuuchi K, Aoki K, et al.

    Ocular immunology and inflammation 2017; (25(sup1)):S15-S18 doi:10.1080/09273948.2016.1184286.

    PMID: 27438588
  13. 13

    Atypical presentation of acute retinal necrosis mimicking Vogt-Koyanagi-Harada disease leading to misdiagnosis: a case report.

    Zhu W, Yu C, Guo Q, et al.

    Frontiers in medicine 2024; (11()):1468801 doi:10.3389/fmed.2024.1468801.

    PMID: 39650189
  14. 14

    Masquerade syndrome: A review of uveitic imposters.

    Dutta Majumder P, Khetan V, Biswas J

    Asia-Pacific journal of ophthalmology (Philadelphia, Pa.) 2024; (13(2)):100054 doi:10.1016/j.apjo.2024.100054.

    PMID: 38583526
  15. 15

    Neoplasia and intraocular inflammation: From masquerade syndromes to immunotherapy-induced uveitis.

    Touhami S, Audo I, Terrada C, et al.

    Progress in retinal and eye research 2019; (72()):100761 doi:10.1016/j.preteyeres.2019.05.002.

    PMID: 31091471
  16. 16

    [Uveitis Masquerade Syndrome: Typical Symptoms and Presentations].

    Biewald E, Rating P, Bechrakis NE, Lommatzsch AP

    Klinische Monatsblatter fur Augenheilkunde 2020; (237(5)):614-620 doi:10.1055/a-1120-8787.

    PMID: 32434245
  17. 17

    Paediatric Neoplastic Uveitis Masquerade Syndromes.

    Asghar E, Puthussery JC, de Boer J, Miraldi Utz V

    Ocular immunology and inflammation 2026; (34(2)):229-241 doi:10.1080/09273948.2025.2594660.

    PMID: 41401403
  18. 18

    A typical Vitelliform-Like Maculopathy Secondary to Bartonella henselae Neuroretinitis.

    Illiano W, Crosson J

    Journal of vitreoretinal diseases 2026; 24741264261418514 doi:10.1177/24741264261418514.

    PMID: 41727755
  19. 19

    Topical Corticosteroids for Infectious Keratitis Before Culture-Proven Diagnosis.

    Hirano K, Tanaka H, Kato K, Araki-Sasaki K

    Clinical ophthalmology (Auckland, N.Z.) 2021; (15()):609-616 doi:10.2147/OPTH.S297202.

    PMID: 33623362

This page explains the biological causes of uveitis for educational purposes only. Always consult your ophthalmologist or specialist for proper diagnosis, testing, and treatment of eye inflammation.

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