A 28-year-old woman from Mumbai with a history of recurrent oral and genital ulcers presents with acute onset of floaters and blurred vision in both eyes over 2 days. Fundoscopy reveals multiple retinal infiltrates with hemorrhages in a 'cottage cheese and ketchup' appearance, along with vitritis. The anterior chamber is quiet with minimal cell infiltration. HLA-B51 is positive. What is the most likely diagnosis?

Explanation

## Diagnosis: Behçet Disease ### Clinical Presentation Analysis **Key Point:** The combination of recurrent oral and genital ulcers (mucocutaneous manifestations), acute bilateral posterior uveitis with the pathognomonic 'cottage cheese and ketchup' retinal appearance, and HLA-B51 positivity is diagnostic of Behçet disease. ### Behçet Disease: Diagnostic Criteria **High-Yield:** Behçet disease is a chronic, relapsing-remitting systemic vasculitis. Diagnosis requires **recurrent oral ulcers (mandatory)** plus 2 of the following: - Recurrent genital ulcers - Ocular involvement (uveitis) - Skin lesions - Positive pathergy test This patient meets criteria with oral ulcers, genital ulcers, and ocular involvement. ### Ocular Manifestations of Behçet Disease | Feature | Anterior Uveitis | Posterior Uveitis (This Case) | |---------|------------------|-------------------------------| | **Frequency** | 70–80% of cases | 50–60% of cases | | **Presentation** | Acute, recurrent | Acute, bilateral, severe | | **Anterior Chamber** | Mild-to-moderate cell infiltration | Quiet (minimal AC involvement) | | **Vitreous** | Clear or mild haze | Dense vitritis with infiltrates | | **Retinal Findings** | — | **'Cottage cheese and ketchup'** = retinal infiltrates + hemorrhages | | **Severity** | Usually mild | Often severe, can cause blindness | | **Laterality** | Often unilateral | Usually bilateral | **Clinical Pearl:** The **'cottage cheese and ketchup' appearance** (also called **'tomato catsup' fundus**) is the hallmark retinal finding in Behçet posterior uveitis—white retinal infiltrates mixed with retinal hemorrhages in a granular pattern. ### Pathophysiology **Mnemonic for Behçet Manifestations:** **ABCD** = **A**phthous ulcers (oral, mandatory), **B**lind (ocular involvement, posterior uveitis), **C**ircumscribed genital ulcers, **D**ermatologic (erythema nodosum, papulopustular lesions) 1. **Systemic vasculitis** — small, medium, and large vessel involvement 2. **Immune mechanism** — T-cell mediated; HLA-B51 association (>90% in East Asian and Mediterranean populations) 3. **Ocular involvement** — retinal vasculitis → infiltrates, hemorrhages, necrosis ### Why Behçet Over Other Posterior Uveitis Causes? | Diagnosis | Mucocutaneous Ulcers | HLA-B51 | Retinal Appearance | AC Reaction | |-----------|----------------------|---------|-------------------|-------------| | **Behçet** | Oral + genital | Positive | Cottage cheese & ketchup | Quiet | | **ARN** | None | Negative | Hemorrhagic necrosis, peripheral | Variable | | **CMV** | None | Negative | Granular, hemorrhagic (immunocompromised) | Quiet | | **FBA** | None | Negative | Frosted branch pattern | Mild | **High-Yield:** The **quiet anterior chamber with severe posterior involvement** is characteristic of Behçet disease and distinguishes it from other posterior uveitis causes. ### Differential Diagnosis **Acute Retinal Necrosis (ARN):** - Caused by HSV-1, HSV-2, or VZV - Presents with **peripheral hemorrhagic retinal necrosis** (not cottage cheese appearance) - Anterior chamber reaction is **more prominent** than in Behçet - No mucocutaneous ulcers; no HLA-B51 association - Requires PCR confirmation and IV acyclovir **Cytomegalovirus (CMV) Retinitis:** - Occurs in severely immunocompromised patients (CD4 <50 cells/μL) - **Granular hemorrhagic appearance** without the white infiltrates of Behçet - No systemic manifestations; no HLA-B51 - Requires CD4 monitoring and antiretroviral therapy **Frosted Branch Angiitis (FBA):** - Rare idiopathic or secondary vasculitis - **Frosted branch pattern** (perivascular sheathing) on retina - Minimal anterior chamber reaction - No mucocutaneous ulcers; no HLA-B51 ### Management of Behçet Posterior Uveitis 1. **Acute phase:** - Systemic corticosteroids: Prednisolone 1 mg/kg/day, taper over 8–12 weeks - Topical corticosteroids: Prednisolone acetate 1% QID - Cycloplegic: Tropicamide 1% TID 2. **Immunosuppression (for recurrent or severe disease):** - **First-line:** Azathioprine 1–2.5 mg/kg/day or mycophenolate mofetil 1–3 g/day - **Second-line:** Infliximab (TNF-α inhibitor) — highly effective for ocular Behçet - Methotrexate: Alternative if azathioprine fails 3. **Monitoring:** - Regular ophthalmology follow-up (monthly during acute phase) - Screen for steroid-induced glaucoma and cataract - Monitor for systemic vasculitis (vascular ultrasound, imaging as needed) **Warning:** Behçet posterior uveitis is **one of the most vision-threatening forms of uveitis**. Untreated, it can lead to blindness in 25% of patients within 5 years. Early aggressive immunosuppression is critical. [cite:Kanski Clinical Ophthalmology 9e Ch 9; Harrison 21e Ch 335]