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Childhood Cancer Types — Genetics Guide for Parents
Hereditary retinoblastoma — the RB1 gene and what it means for your family
Medically reviewed by Dr. C. Raghavendra Reddy, DM (Medical Oncology, Gold Medal) · Last reviewed June 2026
If a doctor has told you that your child’s retinoblastoma may be hereditary — or that there is a change in the RB1 gene — you are likely carrying many questions about what this means for your child, your other children, and your wider family. Hereditary retinoblastoma is a genetic form of eye cancer that arises in very young children. When it is identified and managed at a specialist centre, most children do well — and knowing the genetic picture early gives you the power to protect siblings and future family members too. This page explains the condition clearly and honestly.
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Understanding hereditary retinoblastoma
What the RB1 gene change means — the four things every parent should understand
A diagnosis of hereditary retinoblastoma brings medical, genetic, and emotional questions all at once. Understanding the key concepts — what the RB1 gene does, how hereditary disease differs from non-hereditary, and what it means for your family — helps you ask the right questions and make informed decisions alongside your child’s team.
The key distinction
Hereditary vs Non-Hereditary Retinoblastoma
Retinoblastoma is a cancer of the retina — the light-sensitive layer at the back of the eye — that develops in very young children. The hereditary form arises when a child is born with a change in one copy of the RB1 gene in every cell of their body. This inherited change means every retinal cell already carries one of the two changes needed for a tumour to form, making it much easier for tumours to develop — often in both eyes and at a younger age. In the non-hereditary form, both gene changes happen by chance in a single retinal cell after birth, so the disease tends to be confined to one eye and is not passed down to the affected person’s own children. Knowing which form your child has changes everything: it determines how siblings are screened, how closely your child is watched over time, and whether other family members need genetic testing.
- Hereditary form: change in RB1 gene is present in every body cell from birth
- Often affects both eyes; onset is typically earlier in infancy
- Non-hereditary form: both changes happen by chance in one retinal cell only
How the gene causes cancer
The RB1 Gene — How a Missing Brake Leads to a Tumour
The RB1 gene is a tumour suppressor — its job is to produce a protein that acts as a brake on how fast cells divide. A healthy cell has two working copies of this gene. In hereditary retinoblastoma, one copy is already non-functional at birth (inherited from a parent, or arising as a new change in the egg or sperm). When a second, random change knocks out the remaining working copy in a retinal cell, the brake is gone entirely. That cell can now divide without limit, forming a tumour. This two-hit model explains why children with the hereditary form develop multiple tumours more easily — each retinal cell is already one step away from losing both brakes. In the non-hereditary form, both hits must happen by chance in the same single cell, which is a much rarer event. Understanding this helps families grasp why the hereditary form is more likely to affect both eyes, and why relatives may benefit from testing even before any tumour appears.
- RB1 encodes a protein that controls cell division cycles
- Two non-functioning copies in one cell are needed to start a tumour
- Children with one inherited change reach this threshold much more easily
Familial retinoblastoma genetics
How Hereditary Retinoblastoma Passes Through Families
Hereditary retinoblastoma follows an autosomal dominant inheritance pattern — meaning that one changed copy of the RB1 gene, inherited from one parent, is enough to place a child at high risk of developing the disease. If one parent carries the RB1 gene change, each child has approximately a one-in-two chance of inheriting it. However, inheriting the change does not guarantee that a tumour will form — there is a high but not absolute chance of a tumour developing. Sometimes the gene change arises for the first time in a child with no family history (a de novo mutation); in this situation, the parents themselves are not carriers, but the affected child will be able to pass the change on to their own children in future. This complexity is exactly why a clinical genetics consultation is a vital part of the journey for every family affected by hereditary retinoblastoma. A genetics team can determine precisely which situation your family is in and what testing is recommended for each relative.
- Autosomal dominant: one changed copy is sufficient to elevate risk
- Can arise for the first time (de novo) with no prior family history
- Genetic counselling clarifies the specific risk for each family member
What to look for
The Signs That Prompt Investigation in Young Children
Retinoblastoma most often makes itself visible to parents through specific eye changes that are worth knowing. The most recognised sign is leukocoria — a white or yellowish glow or reflection seen in the pupil, sometimes called the “cat’s eye reflex.” Parents often notice this in photographs taken with a flash, where the affected eye shows a white or pale reflection instead of the usual red-eye effect. A squint (misalignment of the eyes), a change in the colour of the iris, or redness and pain in the eye can also be warning signs. Because retinoblastoma is most effectively treated when detected early — before the tumour has had time to grow large or spread beyond the eye — any of these signs in an infant or young child should prompt a prompt ophthalmological assessment. In children with a known family history of retinoblastoma, planned screening examinations begin from birth or early infancy, before any sign is visible.
- White glow or reflection in the pupil, especially visible in photographs
- Squint or misalignment of the eyes in a young child
- Redness, pain, or change in iris colour — less common early signs
Retinoblastoma is one of several eye- and vision-related warning signs covered in CION’s childhood cancer guides. For a broader overview, visit the Pediatric Cancer hub. If you noticed a white glow or unusual reflection in your child’s eye, see also our guide to white glow in a child’s eye and our page on squint and vision changes in children.
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The clinical journey for your family
From first sign to genetic counselling — what to expect at each step
If your child has been referred with a suspected eye tumour, or if you have a family history of retinoblastoma and are seeking screening for a newborn sibling, this pathway gives you a clear picture of the steps ahead. Every family’s journey is slightly different — your child’s team will explain what applies in your specific situation.
Eye examination under anaesthesia (EUA)
The first definitive step is an examination of both retinas while the child is under a brief general anaesthetic. This allows the ophthalmologist to look at every part of the retina clearly and systematically, document the size, number, and location of any tumours using specialist imaging, and check whether the other eye is also affected. Parents often find the idea of general anaesthesia in a young child alarming — it is important to know that these examinations are short and are performed routinely in specialist paediatric settings. The information gained from the EUA is the foundation of the entire treatment plan. If tumours are found in both eyes, or if the child has a relevant family history, hereditary retinoblastoma is strongly suspected at this point.
Imaging to assess the eye and check for spread
An MRI scan of the brain and orbits (eye sockets) is typically performed to assess how large the tumour is within the eye, whether the optic nerve is involved, and whether there are any signs of the tumour spreading beyond the eye itself into the surrounding tissues or the central nervous system. A chest X-ray or CT chest may be performed if there is any concern about spread to other organs, though this is uncommon in early-stage disease. The imaging results, combined with the EUA findings, allow the multidisciplinary team to assign a group classification to the tumour — a clinical staging system used to guide treatment decisions. Families will receive a clear explanation of what the imaging shows and what it means for next steps.
Multidisciplinary tumor board review before treatment
At CION, no child with retinoblastoma proceeds to treatment without the case being reviewed at a multidisciplinary tumor board. The team includes paediatric medical oncologists, surgical oncologists, ophthalmologists, and radiation oncologists. Together they review the EUA findings, imaging results, the child’s age and overall health, and the family’s specific circumstances. The tumor board produces a written treatment plan — with a cost breakdown — before any treatment begins. This is the “Decisions for healing, not billing” commitment in practice: the team’s recommendation is based on evidence and what is right for your child, not on what generates the most treatment activity.
Treatment — tailored to the tumour and the eye
Treatment for retinoblastoma is highly individualised. Small tumours confined to the retina are often treated with focal approaches: laser therapy (photocoagulation) or cryotherapy applied directly to the tumour, or intravitreal chemotherapy (injected into the gel of the eye). Larger tumours or those involving more of the eye may be treated with intra-arterial chemotherapy — a technique in which medication is delivered directly into the artery that supplies the eye, allowing a high concentration of treatment to reach the tumour with reduced exposure to the rest of the body. Systemic (intravenous) chemotherapy is used when both eyes are involved, when the tumour is very large, or when there is concern about the optic nerve. When a tumour is so advanced that the eye cannot be saved, and to prevent spread, surgical removal of the eye (enucleation) is sometimes the safest option. In all cases, the goal is to treat the cancer thoroughly while preserving as much vision as can safely be preserved.
Why genetic testing matters even when your child is already being treated
Knowing the exact RB1 gene change in your child enables the family to take protective action for others. Newborn siblings of a child with confirmed hereditary retinoblastoma can be offered scheduled eye examinations from birth — so that if a tumour starts to form, it is found at the earliest, most treatable stage. Without this knowledge, a sibling’s tumour might not be noticed until it has grown enough to cause visible signs. The weeks between a tumour forming and it becoming visible can matter enormously for preserving the eye and the vision in it.
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RB1 genetic testing — confirming hereditary status
Once the clinical picture suggests hereditary retinoblastoma — tumours in both eyes, a positive family history, or early onset in infancy — a blood sample from the child is sent for RB1 gene analysis. This test looks for the specific change in the RB1 gene that is present in every cell of the child’s body. When the change is found, it confirms germline (hereditary) status. This result is then used to offer predictive testing to parents and siblings: a simple blood test can tell you whether a parent also carries the mutation (and therefore may have unknowingly passed it on), and whether each sibling of the affected child has inherited it. Siblings who test positive for the mutation begin structured screening examinations; siblings who test negative do not require the same surveillance programme. If the blood test does not find a change in the RB1 gene but the clinical picture still suggests hereditary disease, tumour tissue itself may be tested to look for both changes within the cancer cells.
Genetic counselling — understanding what the result means for your whole family
A genetic counselling consultation brings together the test results, the inheritance pattern, and your family’s specific structure to give you a clear, personalised picture of risk. The genetic counsellor will explain the probability that each family member is a carrier, what options are available for family planning in the future (including pre-implantation genetic testing for families who want to prevent the mutation from being passed to future children), and what long-term surveillance each carrier should have. Parents sometimes feel overwhelmed at this stage — a feeling that is completely understandable. Genetic counselling is not a one-time event; it is an ongoing resource that families can return to as they have more questions. At CION, we coordinate this referral as part of the care plan so that you are not navigating it alone.
Long-term follow-up — structured surveillance for life
Children with hereditary retinoblastoma need lifelong, structured follow-up. In the first years of life, EUAs are performed regularly to detect any new retinal tumours early. As the child grows and can cooperate with standard eye examinations without anaesthesia, the frequency and format of follow-up changes but does not stop. A germline RB1 mutation also carries a lifelong, elevated risk of developing certain other tumours in adulthood — particularly osteosarcoma (a bone tumour) and soft tissue sarcomas, and an elevated risk in areas that received radiation therapy. Long-term surveillance guidelines from specialist societies address these risks. The good news is that having a structured follow-up plan means that if anything new arises, it will be found early, when it is most manageable. Your child’s team will give you a written follow-up schedule so you always know what the next step is and why.
For information about the diagnostic tests your child may need, explore childhood cancer scans and imaging and our guide to how childhood cancer is diagnosed.
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Common questions
Your questions about hereditary retinoblastoma — answered
What is hereditary retinoblastoma and how is it different from the non-hereditary form?
Retinoblastoma is a cancer that develops in the retina — the light-sensitive layer at the back of the eye. It almost always affects young children, usually before the age of five. There are two broad forms. In the hereditary form, the child is born with a change (mutation) in one copy of the RB1 gene in every cell of their body. Because every retinal cell already carries this change from birth, these children are at high risk of tumours developing in both eyes and, in some cases, at other body sites later in life. In the non-hereditary form, both gene changes occur only in a single retinal cell after birth, so the disease tends to affect one eye only and is not passed on to children of the affected person. Distinguishing between these two forms is clinically important — it changes how siblings and future children are screened, and it determines the long-term follow-up plan for the child themselves.
What does the RB1 gene do, and why does a change in it cause retinoblastoma?
The RB1 gene produces a protein called the retinoblastoma protein (pRb), which acts as a critical brake on cell division. In healthy cells, pRb helps to regulate the cycle of cell growth and division, preventing cells from multiplying out of control. When both copies of the RB1 gene in a cell are non-functioning — one change inherited from a parent, and a second change that occurs spontaneously in a retinal cell — the brake is lost entirely. Without it, the affected retinal cell can divide without limit, forming a tumour. This two-hit mechanism, first described by Dr. Alfred Knudson, is the foundation of our understanding of hereditary retinoblastoma and many other hereditary cancer syndromes. A child with a hereditary RB1 mutation needs only one additional random change in any retinal cell for a tumour to start — which is why multiple tumours and earlier onset are characteristic of the hereditary form.
If one of my children has hereditary retinoblastoma, what is the chance that my other children or future children will be affected?
Hereditary retinoblastoma follows an autosomal dominant inheritance pattern. If a child has a confirmed germline (hereditary) RB1 mutation, each first-degree relative — siblings, parents, and future children — has a meaningful chance of carrying the same mutation. The exact probability depends on how the mutation arose: if one parent also carries the mutation, each future child has approximately a one-in-two chance of inheriting it. If the child's mutation arose for the first time (de novo), parents and existing siblings are at much lower risk, but future children of the affected child still face a significant risk when they grow up. Because the consequences of a missed diagnosis are serious — a retinoblastoma that grows undetected can threaten the eye and, in advanced cases, spread — genetic counselling and planned screening for siblings and future children is strongly recommended. Your oncology team will refer you to a clinical genetics service for a full family assessment.
How is hereditary retinoblastoma diagnosed — what tests are involved?
Diagnosis begins with an examination of the retina under anaesthesia, which allows the ophthalmologist to see the retina clearly and document any tumours in both eyes. If tumours are found in both eyes, or if tumours are found in one eye of a child with a family history of retinoblastoma, hereditary disease is strongly suspected. Genetic testing of a blood sample is then performed to look for a mutation in the RB1 gene. This is the definitive test for confirming germline (hereditary) status. Finding the specific mutation in the child is important because it enables targeted, predictive testing of other family members — a sibling or parent can have a blood test to determine whether they carry the same mutation, even before any tumour appears. If the genetic test on a blood sample is negative but clinical features still suggest hereditary disease, tumour tissue may be tested to look for both RB1 changes directly in the cancer cells.
What does treatment for hereditary retinoblastoma involve, and can the eye be saved?
Treatment for retinoblastoma depends on the size, number, and location of the tumours, and whether one or both eyes are involved. The goal, wherever safely possible, is to treat the tumours while preserving as much useful vision as possible. Treatments may include focal approaches — laser therapy or cryotherapy applied directly to small tumours — as well as chemotherapy delivered either through the blood or, in specialist centres, directly into the artery supplying the eye (intra-arterial chemotherapy), or directly into the eye fluid (intravitreal chemotherapy). Radiation therapy is used in selected situations. When tumours are very advanced and the eye cannot be saved, surgical removal of the eye (enucleation) may be the safest option to ensure no tumour cells spread outside the eye. At CION, every child with retinoblastoma is discussed at a multidisciplinary tumor board before treatment begins — surgical oncologists, medical oncologists, radiation oncologists, and ophthalmologists review the case together so that the most appropriate, personalised plan is made.
What long-term follow-up does a child with hereditary retinoblastoma need?
Children with hereditary retinoblastoma need structured, long-term follow-up for several reasons. First, new tumours can continue to develop in the retina of either eye throughout early childhood, so regular examinations under anaesthesia are performed — typically every few weeks in infancy, becoming less frequent as the child grows older. Second, individuals with a germline RB1 mutation carry a lifelong, elevated risk of developing certain other tumours — particularly tumours of the bone and soft tissue, and cancers in areas that received radiation — so ongoing surveillance as they move into adulthood is part of the recommended care plan. Third, vision monitoring and support is important, as treatment can affect visual development. Regular eye examinations and, where indicated, vision therapy help to maximise the child's functional sight. Your child's oncology team will give you a personalised follow-up schedule and explain what each clinic visit is looking for.
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