Clinical Scenario:
A 2-year-old boy is brought to the ophthalmology clinic because his parents have noticed a white reflex in his left eye in several recent photographs. They also report new-onset strabismus. There is no history of trauma or fever. Ocular examination confirms leukocoria. Ocular ultrasonography demonstrates an intraocular mass containing multiple calcified foci.
What is the most likely diagnosis?
A. Coats disease
B. Congenital cataract
C. Ocular toxocariasis
D. Persistent fetal vasculature
E. Retinoblastoma
Correct answer & Explanation:
Correct Answer: E. Retinoblastoma
Explanation
This 2-year-old boy has retinoblastoma, the most likely diagnosis given the combination of leukocoria, new-onset strabismus, and an intraocular mass containing calcification on ultrasonography.
The key clues are:
- Leukocoria (white pupillary reflex): This is the most common presenting feature of retinoblastoma and may first be noticed in flash photographs.
- Strabismus: The second most common presenting feature, often associated with macular involvement.
- Age 2 years: Retinoblastoma is predominantly a tumor of early childhood, with approximately two-thirds of cases diagnosed before 2 years of age.
- Intraocular mass with calcification: This is the classic imaging clue. Ocular ultrasound demonstrating a hyperechoic intraocular mass with calcified foci is highly characteristic of retinoblastoma.
Retinoblastoma is a malignant tumor arising from the retina. It may remain confined to the eye or extend into the optic nerve, orbit, and, in advanced disease, beyond the orbit. Because early diagnosis improves the possibility of preserving vision and the eye, leukocoria in a child requires urgent ophthalmologic assessment.
Why the other options are incorrect
A. Coats disease
Coats disease can cause leukocoria and retinal detachment, but it is characterized by retinal telangiectasia and extensive subretinal exudation rather than a calcified intraocular tumor. It usually occurs in older children, particularly boys. Calcification on ultrasound strongly favors retinoblastoma.
B. Congenital cataract
A congenital cataract can produce leukocoria, but the abnormality is an opacity of the lens, not a solid intraocular mass with calcified foci. Cataract therefore does not explain the ultrasound findings.
C. Ocular toxocariasis
Ocular toxocariasis can produce unilateral leukocoria and a peripheral retinal mass, but it is more commonly associated with ocular inflammation, including vitritis, anterior chamber cells, pain, or photophobia. A calcified intraocular mass is much more characteristic of retinoblastoma.
D. Persistent fetal vasculature (PFV)
PFV is a congenital developmental abnormality that usually presents with unilateral leukocoria, often in a microphthalmic eye, and may be associated with cataract and a retrolental fibrovascular stalk. It does not characteristically produce a calcified intraocular tumor.
E. Retinoblastoma — Correct
The combination of leukocoria + strabismus + an intraocular mass with calcification is classic for retinoblastoma. On ultrasound, calcification within an intraocular mass is an especially important distinguishing feature.
High-yield exam pearl
Child + leukocoria + calcified intraocular mass = retinoblastoma until proven otherwise.
Remember the classic presentation:
Leukocoria → most common
Strabismus → second most common
Calcified intraocular mass → highly characteristic imaging finding
Retinoblastoma also has potential for CSF and systemic spread, so evaluation of the extent of disease is important. Current NCI guidance describes ocular examination, ultrasonography and MRI as key components of diagnostic evaluation.
Reference
PDQ® Pediatric Treatment Editorial Board. Retinoblastoma Treatment (PDQ®)–Health Professional Version. National Cancer Institute.
You can also practice another MCQ on Pallor & Irritability in a Child.
