What is the diagnosis for a child presenting with leukocoria (absent red reflex) in one eye, with normal development?

Retinoblastoma

In a child presenting with unilateral leukocoria (absent red reflex) and normal development, retinoblastoma must be assumed until proven otherwise and requires urgent ophthalmologic evaluation within one week. 1, 2

Why Retinoblastoma is the Primary Diagnosis

• Retinoblastoma is the most common primary intraocular malignancy of childhood and the most likely diagnosis in infants presenting with unilateral leukocoria. 1, 2

• The mean age at diagnosis is 24 months for unilateral tumors and 12 months for bilateral tumors, making this presentation at any age in early childhood highly concerning for malignancy. 2

• Leukocoria is the most common presenting sign of retinoblastoma (75% of cases), and parents typically notice this abnormality before healthcare providers. 2, 3

• If untreated, almost all patients die of intracranial extension and disseminated disease within two years, making prompt diagnosis critical. 2

Why Not the Other Options

Congenital Cataract (Option C)

• While congenital cataract can cause leukocoria, it is less common than retinoblastoma in infants presenting with this finding. 1

• Cataracts are the most common cause of leukocoria overall in pediatric populations (79.76% in one series), but this includes all ages up to 10 years and bilateral cases. 4

• The absence of calcification on imaging helps differentiate cataract from retinoblastoma—cataracts do not calcify, while retinoblastoma characteristically shows calcifications on CT. 5, 1

Toxocariasis (Option A)

• Ocular toxocariasis is extremely uncommon at 6 weeks of age and typically presents in older children, making it an unlikely diagnosis in this age group. 1

• Toxocariasis results from larval granulomatosis and requires environmental exposure to contaminated soil or contact with infected puppies, which is less likely in very young infants. 5

Critical Management Algorithm

1. Immediate referral to pediatric ophthalmology—do not delay while attempting outpatient workup, as leukocoria in an infant is an ophthalmologic emergency. 1

2. Fundoscopic examination and ocular ultrasound are the primary diagnostic tools performed by the ophthalmologist. 5, 1

3. MRI of head and orbits with and without IV contrast is the most useful imaging modality for evaluating suspected retinoblastoma, showing retrolaminar optic nerve infiltration, choroid-scleral involvement, orbital invasion, and intracranial spread. 5, 1, 6

4. CT with IV contrast may be helpful for detecting characteristic calcifications that differentiate retinoblastoma from benign mimics like Coats disease, PHPV, or retinopathy of prematurity. 5, 1

5. Avoid CT as first-line imaging when possible to reduce radiation exposure in a population at considerable risk of second malignancies, particularly in hereditary cases. 7

Critical Pitfalls to Avoid

• Never delay referral based on normal development—retinoblastoma does not affect systemic development until late stages with intracranial extension. 1, 2

• Do not start corticosteroid treatment before ophthalmologic examination, as this may worsen infectious conditions or mask accurate diagnosis. 1

• Do not reassure parents if you cannot appreciate an absent red reflex yourself—children whose parents complain of leukocoria should be referred promptly regardless of whether the physician appreciates the finding. 3

• Office evaluation for red reflex should be performed at every well-child visit until three years of age to detect retinoblastoma early. 2