Diagnosis: Retinoblastoma
Despite the stable, non-progressive nature of the calcifications and absence of family history, retinoblastoma remains the most likely diagnosis in this 1-year-old with leukocoria and retinal calcifications. 1
Key Diagnostic Reasoning
Calcifications Are Pathognomonic for Retinoblastoma
The American College of Radiology explicitly states that the presence of calcifications within well-demarcated retinal lesions in a child with leukocoria is pathognomonic for retinoblastoma. 1
The absence of calcification on imaging is what differentiates Coats disease and persistent hyperplastic primary vitreous (PHPV) from retinoblastoma—meaning the presence of calcifications strongly indicates retinoblastoma, not these other conditions. 2, 1
Calcifications would NOT be present in Coats disease, which rules out option B. 1
Age and Presentation Fit Retinoblastoma Profile
Retinoblastoma is the most common intraocular malignancy in childhood, with leukocoria being the most frequent presenting sign (occurring in 51-86% of cases). 3, 4
The typical age of presentation for unilateral retinoblastoma is approximately 36 months, though bilateral hereditary forms present earlier at 18-24 months. 5
This 1-year-old infant falls well within the expected age range for retinoblastoma diagnosis. 5
Family History Does Not Rule Out Retinoblastoma
Family history may be absent in hereditary cases due to de novo germline RB1 pathogenic variants or variants with reduced penetrance. 5
Approximately 15% of unilateral retinoblastoma cases are hereditary despite appearing sporadic. 6
The National Comprehensive Cancer Network recommends germline testing for all children with retinoblastoma regardless of laterality or family history. 5
"Stable" Appearance Is a Clinical Pitfall
The description of "stable non-progressive" calcifications may reflect a single examination or short observation period, which does not exclude retinoblastoma. 7
The American College of Radiology emphasizes that retinoblastoma must be assumed until proven otherwise in any child presenting with leukocoria. 1
Delayed diagnosis of retinoblastoma leads to advanced disease stages and poor outcomes, making early recognition critical. 8
Why Other Options Are Less Likely
Toxoplasmosis (Option A)
- Ocular toxoplasmosis (toxocariasis) can cause leukocoria but typically does not present with prominent retinal calcifications as a primary feature. 7, 9
- The presence of calcifications makes retinoblastoma far more likely. 1
Coats Disease (Option B)
- Coats disease explicitly does NOT have calcifications—the absence of calcification is what differentiates it from retinoblastoma. 2, 1
- Coats disease presents with normal-sized globes and exudative retinal detachment without calcification. 2
Critical Clinical Action
Never delay ophthalmologic referral—leukocoria in a child is an ophthalmologic emergency requiring immediate evaluation to exclude retinoblastoma, a life-threatening malignancy. 1
Infants or children with retinoblastoma or other tumors of the eye and orbital area should be referred to a pediatric ophthalmologist. 2
MRI of the head and orbits with and without IV contrast is the most useful imaging modality for evaluating suspected retinoblastoma, assessing optic nerve involvement, and detecting intracranial spread. 2