## Arlt's Line — Pathognomonic Sign of Chronic Trachoma **Key Point:** Arlt's line is a horizontal linear scar on the upper tarsal conjunctiva that is pathognomonic for previous severe trachomatous inflammation and indicates chronic or healed trachoma. ### Pathophysiology of Arlt's Line 1. Repeated cycles of Chlamydia trachomatis infection (serovars A, B, Ba, C) 2. Chronic inflammation → fibrosis of the tarsal conjunctiva 3. Horizontal scar forms at the junction of the upper tarsal conjunctiva 4. Represents the demarcation between inflamed and normal conjunctival tissue ### Clinical Features of Chronic Trachoma | Feature | Description | |---------|-------------| | **Arlt's line** | Horizontal scar on upper tarsal conjunctiva (pathognomonic) | | **Trichiasis** | Inturned eyelashes due to tarsal scarring | | **Entropion** | Inversion of eyelid margin from conjunctival contraction | | **Pannus** | Vascular infiltration of superior cornea | | **Herbert's pits** | Depressions on the limbus (upper) | | **Conjunctival xerosis** | Drying from loss of goblet cells | **High-Yield:** Arlt's line is a direct indicator of previous severe trachomatous disease and is used in epidemiological surveys to assess the burden of trachoma in populations. **Clinical Pearl:** Trachoma is the leading infectious cause of blindness worldwide, particularly in resource-limited settings. Early recognition and treatment prevent progression to scarring and blindness. 
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