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An 18-month-old is brought in after the parents notice a white glow in the right eye in photographs. Fundoscopic exam reveals a retinal mass. There is no family history of eye cancer.
RB1 gene (tumor suppressor) - "two-hit" model
- Heritable (~40%): germline variant + somatic second hit; bilateral, younger onset
- Non-heritable (~60%): two somatic hits; unilateral, older onset
- Leukocoria (white pupil reflex) - most common presenting sign
- Strabismus
- Mean age at diagnosis: ~18 months (bilateral) or ~24 months (unilateral)
- Heritable form: risk for second primary tumors (osteosarcoma, melanoma)
- Dilated fundoscopic exam under anesthesia reveals the retinal tumor; leukocoria prompts urgent ophthalmology referral
- Imaging (ultrasound, MRI) characterizes the tumor and assesses optic nerve and orbital extension (CT avoided to limit radiation in germline carriers)
- RB1 molecular testing distinguishes heritable (germline variant, typically bilateral) from non-heritable (sporadic unilateral) disease and guides relative testing
RB one (RB1) = tumors of Retina + Bone Bilat. retinoblasoma → germline variant in RB
- Children with germline RB1 variant need serial dilated fundus exams under anesthesia