A 32-year-old woman presents with unilateral eye pain, photophobia, and blurred vision for 3 days. Slit-lamp examination reveals branching dendritic ulcers with terminal bulbs on the cornea. Which feature best distinguishes this condition from varicella zoster virus (VZV) keratitis?

Question

Accepted Answer

C. Presence of terminal bulbs at the ulcer margins. ## Distinguishing HSV from VZV Keratitis

### Clinical Presentation Comparison

| Feature | HSV Keratitis | VZV Keratitis |
|---------|---------------|---------------|
| **Ulcer morphology** | Dendritic with terminal bulbs | Pseudodendritic (broader, more amorphous) |
| **Terminal bulbs** | Present (pathognomonic) | Absent |
| **Anterior uveitis** | Mild to moderate (common) | Severe, granulomatous |
| **Skin involvement** | Vesicles on lid margin (may be absent) | Dermatomal vesicular rash (always present) |
| **Recurrence** | Frequent (50% within 2 years) | Rare |
| **Corneal scarring** | Mild | Severe |

**Key Point:** The presence of **terminal bulbs** (small rounded protrusions at the tips of dendritic branches) is the single most reliable morphologic discriminator between HSV and VZV keratitis.

### Pathophysiology

**HSV keratitis:**
- Dendritic ulcers form due to viral cytolysis and cell-to-cell spread along nerve endings
- Terminal bulbs represent accumulation of viral particles and infected epithelial cells at branch tips
- Stains with fluorescein (central ulcer) and rose bengal/lissamine green (edges)

**VZV keratitis:**
- Pseudodendritic ulcers are broader and more irregular
- Caused by viral reactivation in ophthalmic division (CN V1) distribution
- Always accompanied by dermatomal vesicular rash (distinguishing feature clinically)

**High-Yield:** While dermatomal rash is a clinical clue for VZV, it is not always visible at the time of corneal examination. The **terminal bulbs on dendritic ulcers** are the corneal finding that definitively identifies HSV.

**Clinical Pearl:** If you see a dendritic ulcer WITHOUT terminal bulbs but with a dermatomal rash and severe anterior uveitis, think VZV. If you see dendritic ulcers WITH terminal bulbs, HSV is the diagnosis regardless of skin findings.

[cite:Khurana 6e Ch 5]

![Viral Keratitis diagram](https://mmcphlazjonnzmdysowq.supabase.co/storage/v1/object/public/blog-images/explanation/4180.webp)

Answer

A. Involvement of the ophthalmic division of trigeminal nerve

Answer

B. Anterior uveitis as a common association

Answer

D. Vesicular rash on the eyelid and forehead

A 32-year-old woman presents with unilateral eye pain, photophobia, and blurred vision for 3 days. Slit-lamp examination reveals branching dendritic ulcers with terminal bulbs on the cornea. Which feature best distinguishes this condition from varicella zoster virus (VZV) keratitis?

Explanation

Distinguishing HSV from VZV Keratitis

Clinical Presentation Comparison

Pathophysiology

Practice similar questions

Join our NEET PG community

Feature	HSV Keratitis	VZV Keratitis
Ulcer morphology	Dendritic with terminal bulbs	Pseudodendritic (broader, more amorphous)
Terminal bulbs	Present (pathognomonic)	Absent
Anterior uveitis	Mild to moderate (common)	Severe, granulomatous
Skin involvement	Vesicles on lid margin (may be absent)	Dermatomal vesicular rash (always present)
Recurrence	Frequent (50% within 2 years)	Rare
Corneal scarring	Mild	Severe