A 3-year-old girl with a family history of retinoblastoma presents with bilateral intraocular masses detected on routine screening. Genetic testing reveals a RB1 gene mutation. What is the most common presenting sign of retinoblastoma in children?

Explanation

## Presenting Signs of Retinoblastoma **Key Point:** Leukocoria (white pupil reflex or "cat's eye reflex") is the most common presenting sign of retinoblastoma, occurring in 60–80% of cases at presentation. ### Why Leukocoria is Most Common Leukocoria results from the white appearance of the intraocular tumor mass as it reflects light from the retina and vitreous. This sign is highly visible to parents during normal lighting conditions or in photographs (especially flash photography), making it the most frequently noticed abnormality. ### Presenting Signs of Retinoblastoma | Sign | Frequency | Mechanism | |------|-----------|----------| | **Leukocoria** | 60–80% | Tumor mass reflects light; visible to parents | | Strabismus | 15–20% | Tumor affects fovea or causes vision loss | | Eye pain/redness | 10–15% | Secondary glaucoma, inflammation | | Proptosis | 5–10% | Orbital extension of advanced tumor | | Hyphema | <5% | Tumor necrosis or vascular involvement | | Vitreous hemorrhage | <5% | Tumor vasculature rupture | **Clinical Pearl:** Leukocoria is often first noticed by parents in photographs with flash, or during routine eye contact in dim lighting. This makes it a critical screening sign — any child with a persistent white pupil reflex must undergo immediate ophthalmologic evaluation. **High-Yield:** The mnemonic **"LEUKO"** helps recall the most common presentation: - **L**eukocoria (white pupil) - **E**xotropia/Esotropia (strabismus) - **U**veitis (secondary inflammation) - **K**eratitis (from advanced disease) - **O**rbital signs (proptosis in advanced cases) **Mnemonic:** **ABCDE of Retinoblastoma Presentation** — **A**bsence of red reflex (leukocoria), **B**ilateral disease (40% of hereditary cases), **C**hildren <5 years, **D**ecrease in vision/strabismus, **E**xtraocular extension (late sign). **Warning:** Do NOT confuse leukocoria with other causes of white pupil reflex (persistent fetal vasculature, toxoplasmosis, retinopathy of prematurity). However, in a child with a white pupil reflex, retinoblastoma must be ruled out urgently. [cite:Boyd & Melia, Retinoblastoma; Park 26e Ch 12]