Phlyctenular Keratoconjunctivitis
Ophthalmology: Type IV Hypersensitivity Reaction
1. Pathophysiology
Phlyctenulosis is a delayed-type hypersensitivity (Type IV) reaction of the ocular surface, most commonly to bacterial proteins. It represents an immune response to antigens elsewhere in the body.
2. Clinical Features
| Feature | Clinical Characteristic |
|---|---|
| The “Phlycten” | Small, white, elevated nodule at the limbus or on the cornea/conjunctiva, surrounded by a focal injection zone. |
| Associations | Historically linked to Tuberculosis (TB); in developed regions, frequently associated with Staphylococcal blepharitis. |
3. Management & High-Yield Pearls
- Diagnostic Workup: Always screen for occult TB (e.g., PPD skin test or IGRA) if the clinical presentation is suspicious or recurrent.
- Treatment: Topical corticosteroids are highly effective for symptom relief and resolution of the nodule; treat underlying blepharitis with lid hygiene and topical antibiotics if indicated.
- Corneal Involvement: If the phlycten migrates onto the cornea, it can leave behind a “limbal-based” vascularized scar, which may affect visual acuity.
- Educational Resource: For more on hypersensitivity reactions of the eye, clinical imaging, and practice modules, visit mymedschool.org.