Retinoblastoma (Answer: B)
The most likely diagnosis is retinoblastoma, as the presence of calcifications within well-demarcated retinal lesions in a child with leukocoria is pathognomonic for this malignancy and distinguishes it from other causes of leukocoria. 1
Why Retinoblastoma is the Correct Answer
The clinical triad presented—leukocoria, well-demarcated retinal lesions, and calcifications—is diagnostic of retinoblastoma:
Calcifications are the key distinguishing feature: The American College of Radiology explicitly states that the absence of calcification on CT scan is what differentiates PHPV and Coats disease from retinoblastoma, meaning the presence of calcification strongly indicates retinoblastoma. 1
Retinoblastoma accounts for 50% of all childhood leukocoria cases and is the most common intraocular malignancy in children, making it statistically the most likely diagnosis when leukocoria is present. 2, 3
Well-demarcated retinal masses with calcification are characteristic of retinoblastoma, which manifests in a normal-sized eye as a calcified mass that is often partially necrotic and grows into the vitreous. 2
Why Other Options Are Incorrect
Toxocariasis (Option A)
- Toxocaral endophthalmitis accounts for only 16% of leukocoria cases and presents as a granulomatous reaction in the vitreous and uveoretinal coat. 2
- Critically, toxocariasis does NOT typically present with calcifications—it shows hemorrhage without calcification, which excludes it from this case. 2
- Toxocariasis is extremely uncommon in young infants and typically presents in older children. 4
Coats Disease (Option C)
- Coats disease accounts for 16% of leukocoria cases and is characterized by retinal telangiectasia producing lipoproteinaceous subretinal exudate. 2
- The American College of Radiology explicitly states that absence of calcification helps differentiate Coats disease from retinoblastoma, meaning calcifications would NOT be present in Coats disease. 1
- Coats disease shows increased attenuation and signal intensity from hemorrhage but specifically lacks calcification or enhancement. 2
Congenital Rubella (Option D)
- Congenital rubella is not listed among the common causes of leukocoria in children by the American College of Radiology guidelines, which include retinoblastoma, PHPV, retinopathy of prematurity, Coats disease, congenital cataract, and larval granulomatosis. 1
- Rubella-associated ocular findings typically include cataracts and pigmentary retinopathy, not calcified retinal masses with leukocoria.
Critical Clinical Pitfall to Avoid
Never delay ophthalmologic referral while attempting outpatient workup—leukocoria in a child is an ophthalmologic emergency that requires immediate evaluation to exclude retinoblastoma, a life-threatening malignancy. 4, 5 The American College of Radiology emphasizes that retinoblastoma must be assumed until proven otherwise in any child presenting with leukocoria. 4