Behcet Disease (Ocular)

Behçet disease is a chronic relapsing multisystem vasculitis of small and large vessels, characterised by recurrent oral aphthous ulcers, genital ulcers, skin lesions and uveitis, with neurological, vascular and gastrointestinal involvement.

• Highest prevalence along the ancient Silk Road: Turkey (about 20 to 400 per 100,000), Middle East, Iran, Japan, Korea and China; young adults aged 20 to 40 years, men with more severe disease.
• Strong association with HLA-B51; autoinflammatory and autoimmune mechanisms with neutrophil activation.
• Ocular involvement in about 50 to 70 percent, a leading cause of morbidity and blindness (bilateral in 70 to 80 percent); usually within 2 to 3 years of onset.

• Diagnostic criteria: recurrent oral aphthae (at least 3 per year) plus at least two of recurrent genital aphthae, eye lesions (anterior uveitis, posterior uveitis, retinal vasculitis), skin lesions (erythema nodosum, pseudofolliculitis, papulopustular lesions), and positive pathergy test (pustule at the site of a needle prick after 24 to 48 hours).
• Ocular: relapsing remitting non-granulomatous panuveitis with hypopyon (often with minimal redness, the "cold" hypopyon), vitritis, occlusive retinal vasculitis with sheathing, retinal infiltrates and haemorrhages, macular oedema, ischaemic maculopathy, branch retinal vein occlusion, neovascularisation, optic neuropathy, and rarely scleritis.
• Systemic: deep vein thrombosis, arterial aneurysms (pulmonary artery aneurysm, a cause of fatal haemoptysis), cerebral venous sinus thrombosis, parenchymal neurological disease (brainstem), arthritis, gastrointestinal ulceration (ileocaecal).
• Course: each attack leaves damage; repeated episodes cause macular scarring, optic atrophy, cataract, glaucoma.

• Clinical diagnosis based on criteria; there is no specific test. HLA-B51 supports in the appropriate setting.
• Pathergy test; slit lamp, fundus examination and fluorescein angiography (leakage from capillaries and large vessels, ischaemia), optical coherence tomography.
• Exclude other causes: syphilis, tuberculosis, herpes, sarcoid, ANCA vasculitis, inflammatory bowel disease, and multiple sclerosis; vascular imaging (ultrasound, MR angiography, CT pulmonary angiography) when thrombosis or aneurysm is suspected.
• Inflammatory markers (CRP, ESR) and full blood count.

• Posterior or panuveitis (sight threatening) needs prompt systemic immunosuppression:
  • Acute attack: intravenous methylprednisolone 1 g daily for 3 days or oral prednisolone 0.5 to 1 mg/kg daily, tapered; sub-Tenon or intravitreal triamcinolone, or dexamethasone implant for unilateral macular oedema.
  • Azathioprine 2.5 mg/kg daily (the standard first line steroid sparing drug), started at the time of the first posterior segment attack; ciclosporin 3 to 5 mg/kg daily (avoid in neurological disease, nephrotoxicity and hypertension monitoring); mycophenolate and methotrexate as alternatives.
  • Biologics for severe, refractory or macular threatening disease: infliximab 5 mg/kg at weeks 0, 2 and 6 then every 8 weeks (often used first line in severe retinal vasculitis, with rapid response), adalimumab 80 mg then 40 mg every 2 weeks, interferon alfa-2a 3 to 6 million units daily then taper to 3 million units three times weekly (effective but with flu like symptoms and depression), tocilizumab 8 mg/kg every 4 weeks in refractory cases.
• Anterior uveitis alone: topical prednisolone acetate 1 percent and cycloplegic (atropine 1 percent); consider colchicine 0.5 to 1.5 mg daily for mucocutaneous disease, and azathioprine for recurrences.
• Hypopyon: topical steroid, cycloplegic, and systemic therapy.
• Complications: cataract surgery after at least 3 months of quiet inflammation with perioperative steroid cover; glaucoma and neovascularisation (panretinal photocoagulation, anti-VEGF); vitrectomy for non-clearing haemorrhage or tractional detachment.
• Systemic: multidisciplinary care (rheumatology, neurology, vascular). Venous thrombosis is treated with immunosuppression (cyclophosphamide, steroids) rather than anticoagulation alone; anticoagulation is contraindicated when pulmonary artery aneurysm is present.
• Monitor every 1 to 3 months initially; counsel on smoking cessation and early reporting of visual change.