A 28-year-old woman presents to the emergency department with severe left eye pain, photophobia, and blurred vision for 3 days. On examination, she has a unilateral dendritic ulcer on the cornea with branching pattern visible on fluorescein staining. She reports a history of recurrent oral cold sores. Her CD4 count is 450 cells/μL (she is HIV-positive on antiretroviral therapy). What is the most likely diagnosis and the most appropriate immediate management?

Explanation

## Clinical Diagnosis **Key Point:** The dendritic ulcer with branching pattern on fluorescein staining is pathognomonic for HSV keratitis. The history of recurrent oral herpes and unilateral presentation confirm HSV-1 as the causative agent. ## Pathophysiology 1. HSV-1 reactivation from trigeminal nerve latency 2. Anterograde axonal transport to corneal epithelium 3. Lytic infection causing epithelial ulceration with characteristic dendritic morphology 4. Immunocompromised state (CD4 450) increases risk of recurrence and severity ## Management Rationale **High-Yield:** HSV keratitis management follows a stepwise approach: | Stage | Clinical Finding | Management | |-------|------------------|-------------| | Epithelial keratitis | Dendritic ulcer | Topical acyclovir 5% ointment 5× daily ± oral acyclovir | | Stromal keratitis | Stromal infiltration, edema | Topical antivirals + topical corticosteroids (controversial) | | Endotheliitis | Keratic precipitates, anterior chamber reaction | Topical corticosteroids + antivirals | **Clinical Pearl:** Topical corticosteroids are CONTRAINDICATED in epithelial HSV keratitis as they promote viral replication and geographic ulceration. They are only considered in stromal disease under ophthalmologic supervision. **Key Point:** Oral acyclovir 400 mg five times daily (or 800 mg four times daily) for 7–10 days is standard systemic therapy, especially in immunocompromised patients, to reduce recurrence risk and promote healing. ## Why This Patient Needs Systemic Therapy - CD4 < 500 cells/μL indicates moderate immunosuppression - Risk of disseminated HSV infection (encephalitis, hepatitis) - Systemic acyclovir reduces recurrence from ~50% to ~20% at 1 year [cite:Harrison 21e Ch 172]