Most Likely Diagnosis: Retinoblastoma in an Infant with Leukocoria
Retinoblastoma is the most likely diagnosis in an infant presenting with leukocoria and must be assumed until proven otherwise through urgent ophthalmologic evaluation. 1
Why Retinoblastoma is the Primary Concern
Retinoblastoma is responsible for approximately half of all leukocoria cases in infants, making it the most critical diagnosis to exclude due to its life-threatening nature. 2
The American College of Radiology explicitly states that retinoblastoma must be considered the most likely diagnosis in a 6-week-old infant presenting with unilateral leukocoria. 1
Retinoblastoma represents the most common intraocular malignancy of childhood and is fatal if untreated, with leukocoria (white eye reflex) being the most common presenting sign. 3
Alternative Diagnoses to Consider
While retinoblastoma is the primary concern, other conditions can present with leukocoria in infants:
Congenital Cataract
Congenital cataract is actually the most common overall cause of leukocoria in children (60% of cases), but is less common than retinoblastoma specifically in young infants. 4
The lens opacity blocks light transmission, preventing the normal red reflex and creating the white pupillary appearance. 5
Absence of calcification on CT imaging helps differentiate congenital cataract from retinoblastoma. 6, 1
Other Less Likely Diagnoses in Infants
Persistent hyperplastic primary vitreous (PHPV) is associated with microphthalmia and lacks calcification on imaging. 6
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
Coats disease presents with normal-sized globe (unlike PHPV) but lacks the postcontrast enhancement seen with retinoblastoma on MRI. 6
Critical Action Required
The American Academy of Pediatrics recommends that any child with leukocoria requires urgent referral to a pediatric ophthalmologist, as absent red reflex is an absolute indication for specialist evaluation. 5
Never delay referral while attempting outpatient workup—leukocoria in an infant is an ophthalmologic emergency. 1, 7
Conditions like retinoblastoma can result in death if treatment is postponed, emphasizing the need for prompt referral without delay for additional testing or imaging. 5
Diagnostic Approach
Fundoscopic examination and ocular ultrasound performed by the ophthalmologist are the primary diagnostic tools and may establish the diagnosis without requiring additional imaging initially. 6, 7
MRI of head and orbits with and without IV contrast is the gold standard imaging modality once retinoblastoma is suspected, demonstrating retrolaminar optic nerve infiltration, choroid-scleral involvement, orbital invasion, and intracranial spread. 1, 7
CT with IV contrast is helpful for detecting calcifications, which are characteristic of retinoblastoma and aid in differentiating it from benign mimics. 7
Common Pitfall to Avoid
Never assume the diagnosis is benign simply because the infant is developing normally—both congenital cataract and retinoblastoma can present with normal systemic development while causing severe unilateral visual impairment or life-threatening disease. 5