## Arlt's Line: Pathognomonic Sign of Trachoma **Key Point:** Arlt's line is a horizontal band of dense inflammatory infiltrate and scarring on the upper tarsal conjunctiva, pathognomonic for chronic trachoma caused by serovars A, B, Ba, and C of Chlamydia trachomatis. ### Mechanism of Arlt's Line Formation 1. Chronic chlamydial infection triggers persistent inflammation 2. Repeated cycles of infection and healing cause conjunctival scarring 3. Horizontal band forms due to mechanical trauma from blinking and lid movement 4. Results in fibrosis and conjunctival shortening **High-Yield:** Arlt's line is a **stage 3 trachoma** finding (TF—trachomatous inflammation-intense) and indicates progression toward blindness. It is one of the earliest signs of conjunctival scarring and is highly specific for trachoma. ### Trachoma Staging (WHO Simplified Classification) | Stage | Finding | Significance | |-------|---------|---------------| | **TF** | Trachomatous inflammation–intense | Active infection, >5 follicles on upper tarsus | | **TS** | Trachomatous scarring | Conjunctival scarring (includes Arlt's line) | | **TT** | Trachomatous trichiasis | Eyelash inturning | | **TE** | Trachomatous entropion | Eyelid inversion | | **CO** | Corneal opacity | Blindness | **Clinical Pearl:** Arlt's line is a marker of **irreversible conjunctival fibrosis** and indicates that the patient has had repeated infections over years. Once present, it does not regress even with antibiotic treatment. **Mnemonic:** **A-rlt = Anterior-line (upper tarsal)** — it is a horizontal line on the anterior conjunctiva of the upper eyelid. 
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