## Chronic Trachomatous Conjunctivitis — Pathognomonic Signs **Key Point:** Arlt's line is a pathognomonic sign of chronic trachomatous conjunctivitis, representing a linear scar on the superior tarsal conjunctiva caused by repeated inflammation and fibrosis from Chlamydia trachomatis infection. ### Pathognomonic and Characteristic Signs in Conjunctivitis | Sign | Condition | Appearance | Mechanism | | --- | --- | --- | --- | | **Arlt's line** | Chronic trachoma (Chlamydia trachomatis) | Horizontal scar on superior tarsal conjunctiva | Fibrosis from chronic inflammation | | **Horner–Trantas dots** | Vernal keratoconjunctivitis (allergic) | Yellowish nodules at limbus | Eosinophil aggregates | | **Bitot's spots** | Not a conjunctival sign; associated with vitamin A deficiency | Foamy patches on temporal conjunctiva | Keratinization | | **Foville's spots** | Not a standard ophthalmology sign | — | — | | **Herbert's follicles** | Chronic trachoma | Follicles on upper tarsal margin | Chronic lymphoid infiltration | | **Conjunctival xerosis** | Vitamin A deficiency | Dull, wrinkled conjunctiva | Keratinization | **High-Yield:** Arlt's line is specific to chronic trachoma and indicates advanced disease with significant fibrosis. It is a classic NEET PG question stem. **Mnemonic:** **ARLT** = **A**dvanced **R**epeat **L**inear **T**rachoma — a horizontal linear scar on the upper tarsal conjunctiva. **Clinical Pearl:** Chronic trachoma is endemic in parts of India and is a leading infectious cause of preventable blindness worldwide. Arlt's line indicates trichiasis and entropion are likely to follow, necessitating early treatment with azithromycin or doxycycline. ### Pathophysiology Chlamydia trachomatis (serovars A, B, Ba, C) causes chronic follicular conjunctivitis. Repeated cycles of infection and inflammation lead to: 1. Conjunctival scarring (Arlt's line on upper tarsus) 2. Trichiasis (inturned lashes) 3. Entropion (inversion of eyelid margin) 4. Corneal pannus and opacification → blindness if untreated 
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