Which morphological pattern of corneal ulceration is pathognomonic for primary herpes simplex keratitis?

Explanation

## Herpes Simplex Keratitis — Morphological Classification **Key Point:** The dendritic ulcer with terminal bulbae (swollen terminal ends) is the pathognomonic hallmark of primary HSV epithelial keratitis. This branching pattern results from viral replication in epithelial cells and lateral spread of infection. ### Dendritic Ulcer Morphology **High-Yield:** The classic dendritic ulcer has: - **Central ulcerated area** with staining (rose bengal or lissamine green) - **Terminal bulbae** at the ends (swollen, infected epithelial cells) - **Branching, tree-like pattern** resembling a herpes zoster distribution - **Rolled edges** with edematous epithelium ### HSV Keratitis — Stages and Patterns | Stage | Morphology | Staining | Recurrence Risk | Management | | --- | --- | --- | --- | --- | | **Epithelial (Primary)** | Dendritic ulcer with terminal bulbae | Fluorescein (ulcer base), rose bengal (infected cells) | Yes (40–50% recur) | Topical antivirals (acyclovir, ganciclovir) | | **Stromal (Recurrent)** | Disciform infiltration, Descemet's folds, endotheliitis | Minimal fluorescein uptake | Yes | Topical + systemic antivirals + topical steroids | | **Endotheliitis (Immune)** | Keratic precipitates, anterior chamber reaction | Minimal epithelial staining | Yes | Topical steroids + antivirals | **Clinical Pearl:** The terminal bulbae are swollen because they contain actively replicating virus. Touching or rupturing them can spread infection laterally, converting a small dendritic ulcer into a larger amoeboid ulcer if steroids are inadvertently used. **Warning:** Topical corticosteroids are **contraindicated** in HSV epithelial keratitis — they promote viral replication and can cause geographic (amoeboid) ulceration and corneal perforation. Always confirm HSV is ruled out before using steroids in keratitis. **Mnemonic:** **DENDRITIC = Dendritic ulcer, Epithelial, Nucleoside analogs (antivirals), Dendritic pattern with terminal bulbae, Recurrent episodes, Infected epithelium, Terminal bulbae swollen, Infected cells stain with rose bengal, Corneal scarring if recurrent**