Leukocoria in a 14-month-old with a bilateral finding on examination under anaesthesia
A 14-month-old boy is referred because his mother has noticed a white pupillary reflex in his right eye in flash photographs over the past six weeks. He is otherwise well, has no family history of eye tumours or enucleation, and was born at term. Examination under anaesthesia finds normal anterior segments. The right eye has a white, lobulated retinal mass about 9 disc diameters across arising from the posterior pole, with three separate clusters of vitreous seeds and a small amount of subretinal fluid. In the superotemporal periphery of the left eye there is a flat, creamy lesion 2 disc diameters across with no calcification and no seeding. Intraocular pressure is normal in both eyes and the anterior chambers are quiet. B-scan ultrasonography shows intralesional hyperechogenicity with acoustic shadowing in the right eye. The parents ask whether the eye can be saved and whether the left eye is involved.
1. What is the differential diagnosis, and how would you complete the work-up? Explain what you would not do.
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Differential: retinoblastoma is the leading diagnosis - leukocoria, a white retinal mass with intralesional calcification on ultrasound, and vitreous seeding. Alternatives include Coats disease (usually older boys, telangiectasia with exudation, no calcification), persistent fetal vasculature (microphthalmia, stalk from the disc), toxocariasis (usually a solitary granuloma with vitreous bands, older child), medulloepithelioma, retinal detachment from other causes, and, rarely, organising vitreous haemorrhage.
Work-up:
- Examination under anaesthesia with wide-field digital imaging of both eyes, documenting size, location, seeding and subretinal fluid for staging and for comparison at follow-up.
- MRI of the brain and orbits with gadolinium to assess optic nerve invasion, extraocular extension and the pineal region (trilateral retinoblastoma).
- B-scan already done; document calcification.
- Blood for RB1 gene testing, including the possibility of a somatic versus germline mutation, with genetic counselling.
- Baseline audiometry and renal function if systemic chemotherapy is planned; echocardiography if a central line is to be placed.
What not to do: do not perform an intraocular biopsy or diagnostic vitrectomy - the risk of tumour seeding through the needle tract into the orbit and systemic circulation is unacceptable, and the diagnosis is made clinically and radiologically. Avoid CT where possible: the radiation dose matters in a child who may carry a germline RB1 mutation and therefore has an elevated lifetime risk of second cancers. Do not use radiation therapy as a first-line treatment for the same reason.
2. How would you manage the right eye and the left eye, and what determines whether the right eye is enucleated?
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Right eye (advanced intraocular disease with vitreous seeding, likely group D): the aim is globe salvage using systemic chemotherapy (vincristine, etoposide, carboplatin) to shrink the tumour and control seeding, followed by focal consolidation - transpupillary thermotherapy, cryotherapy, or plaque brachytherapy - to treat the residual tumour. Alternative or adjunctive routes include intra-arterial melphalan and intravitreal topotecan or melphalan, which achieve high local concentrations with less systemic toxicity but require specialist centres and carry their own risks (vascular, infectious, and rarely extraocular spread).
Left eye: a small, flat, non-seeded peripheral lesion is treated focally with laser or cryotherapy. If systemic chemotherapy is being given for the right eye, the left lesion can be consolidated during that course. The very presence of a second lesion is diagnostically important: it makes bilateral, and therefore almost certainly germline, disease very likely.
Enucleation of the right eye is indicated if: the tumour cannot be salvaged despite chemotherapy and focal treatment; there is massive vitreous or subretinal seeding with no response; there is neovascular glaucoma, a painful blind eye or massive intraocular haemorrhage; there is suspicion of optic nerve or massive choroidal invasion on imaging (relative indication); or the family prefers enucleation after full counselling, since it gives excellent survival and avoids years of examinations and treatments.
Whichever route is chosen, follow-up under anaesthesia every 3–6 weeks initially is essential, because new seeds and recurrences are common in the first year.
3. What does the bilateral finding mean for the family, and how do you counsel them and organise follow-up?
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Bilateral disease indicates an underlying germline RB1 mutation, even without a family history (most are de novo). Approximately 40% of retinoblastoma patients overall, and almost all with bilateral disease, are germline carriers. The implications require a genetic counselling referral and clear documentation:
- Inheritance: autosomal dominant with about 50% transmission to each child and a high, age-dependent penetrance. Each sibling has up to a 50% risk if a parent carries the mutation; siblings and the child's future offspring need screening.
- Testing: send blood for RB1 mutation analysis, and test parents; if a mutation is found, predictive testing of siblings can be done, and prenatal testing or preimplantation genetic diagnosis can be discussed for future pregnancies.
- Screening for at-risk children: examination under anaesthesia at regular intervals from birth (for example every 1–2 months in the first year, then less frequently) until the child is old enough to co-operate with clinic examination, with parental instruction to watch for leukocoria and strabismus in the interim. The left-eye lesion in this child shows why this matters.
- Second malignancy risk: germline carriers have a substantially increased lifetime risk of osteosarcoma and soft tissue sarcomas, and this risk is highest if they receive radiotherapy. Counsel on sun protection, avoidance of unnecessary radiation, and lifelong surveillance; advise prompt investigation of bone pain or lumps.
- Follow-up of the child: regular EUA to monitor the treated right eye (if salvaged) and the left lesion, plus vision and amblyopia management, orthoptic follow-up, and long-term ophthalmic surveillance for cataract, radiation retinopathy and secondary tumours.
- Practical support: involve a specialist retinoblastoma team, a clinical nurse specialist and family support services; give written information about warning signs and a clear route back to the team.