## Diagnosis: Sjögren Syndrome with Keratoconjunctivitis Sicca **Key Point:** Chronic conjunctivitis in a patient with rheumatoid arthritis, positive Schirmer test (<5 mm), and squamous metaplasia on cytology is pathognomonic for Sjögren syndrome-associated keratoconjunctivitis sicca (KCS). **High-Yield:** Sjögren syndrome is an autoimmune disorder affecting exocrine glands; 50% of RA patients develop secondary Sjögren syndrome. The conjunctival changes reflect chronic dry eye disease, not infection. ### Pathophysiology of Sjögren Syndrome ```mermaid flowchart TD A[Genetic predisposition + Environmental trigger]:::outcome --> B[Autoreactive T and B cells]:::outcome B --> C[Infiltration of lacrimal and salivary glands]:::outcome C --> D[Destruction of acinar epithelium]:::urgent D --> E[Loss of aqueous tear secretion]:::urgent E --> F[Tear film instability]:::outcome F --> G[Epithelial desiccation]:::outcome G --> H[Squamous metaplasia + Goblet cell loss]:::outcome H --> I[Chronic conjunctivitis + KCS]:::outcome ``` ### Diagnostic Criteria for Sjögren Syndrome | Test | Positive Criterion | Interpretation | |------|-------------------|----------------| | Schirmer test | <5 mm in 5 minutes | Aqueous tear deficiency | | Rose Bengal / Lissamine Green | Positive staining | Conjunctival epithelial damage | | Conjunctival impression cytology | Squamous metaplasia, ↓ goblet cells | Chronic dry eye changes | | Tear osmolarity | >308 mOsm/kg | Tear film instability | | Anti-SSA/Ro, Anti-SSB/La antibodies | Positive | Autoimmune marker | | Lip biopsy | Lymphocytic infiltration | Histologic confirmation | **Clinical Pearl:** Squamous metaplasia indicates chronic epithelial damage from desiccation. Normal conjunctiva has columnar epithelium with abundant goblet cells; chronic dry eye causes replacement with stratified squamous epithelium and goblet cell loss. ### Why NOT the Other Options? **Viral infection** would show: - Acute onset, not 6-month chronic course - Follicular response on conjunctiva - Negative Schirmer test (viral conjunctivitis does not cause lacrimal gland destruction) - No squamous metaplasia **Bacterial biofilm** would show: - Purulent discharge (not mucoid) - Positive bacterial culture - Acute exacerbations with fever - No association with RA or autoimmune markers **Allergic conjunctivitis** would show: - Seasonal or episodic pattern - Giant papillae on upper tarsal conjunctiva - Eosinophils on cytology (not squamous metaplasia) - Normal Schirmer test ### Management of Sjögren-Associated KCS 1. **Tear substitutes** — artificial tears, preservative-free 2. **Tear conservation** — punctal plugs or cautery 3. **Cyclosporine 0.05%** — topical immunosuppression to reduce inflammation 4. **Systemic therapy** — hydroxychloroquine, methotrexate for systemic manifestations 5. **Ocular surface protection** — protective eyewear, humidifiers **Warning:** Do not treat Sjögren-associated KCS with topical antibiotics alone — the problem is tear deficiency, not infection. Antibiotics may worsen the condition by further damaging the ocular surface. [cite:Kanski Ophthalmology 9e Ch 3; Harrison 21e Ch 313] 
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