Medical Oncologist
CION Cancer Clinics
Nijmegen breakage syndrome: when both NBN copies are faulty | CION Cancer Clinics
Nijmegen breakage syndrome is a rare condition in children who inherit a faulty NBN gene from both parents. It causes a small head size, slow growth, weak immunity and a strong sensitivity to radiation. It also carries a high risk of lymphoma in childhood. The gene fault cannot be corrected, but specialist care changes a great deal. This page explains the signs, the tests and how care is planned. At CION Cancer Clinics, our oncologists explain what a gene result means for you and your family, and plan the checks that follow.
NG
Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed September 2026, next review due September 2027
17+specialists on panel
15,000+patients treated
35+centres across Telangana & AP
4.8★ / 800+Google rating
On this page
- What is Nijmegen breakage syndrome?
- What are the signs in a child?
- How is the syndrome confirmed?
- What do the doctors' terms mean?
- How is care different for a child with the syndrome?
- What can this page not tell you?
- What do families believe about the syndrome that is not true?
- Common questions about Nijmegen breakage syndrome
The short answer
What is Nijmegen breakage syndrome?
Nijmegen breakage syndrome is a rare condition in children who inherit a faulty NBN gene from both parents. Their cells cannot repair broken DNA properly. This causes a small head size, slow growth, weak immunity, a strong sensitivity to radiation, and a high risk of lymphoma in childhood.
How a child comes to have it
Each parent carries one faulty copy of NBN and is usually perfectly well. When both pass on their faulty copy, the child has no working copy at all. The parents did nothing to cause this, and nothing in the pregnancy could have prevented it.
How rare it is, and where
Most children with the syndrome have been found in Central and Eastern Europe, where one NBN fault is shared by many families. Elsewhere it is very rare, and only a handful of cases have been reported from India. Because it is so rare here, it can take time for doctors to think of it. Families where the parents are related by blood are more likely to be affected.
The name comes from Nijmegen, the Dutch city where doctors first described it.What doctors notice
What are the signs in a child?
No child has every feature, and some become clearer only with time.
Head size and growth
The head is small at birth or soon after, and the difference grows more obvious as the child gets older. Height and weight are often below other children of the same age.
Also seen
- A sloping forehead and prominent middle face
- Learning that slows as the child grows
Weak immunity
Many children have low levels of antibodies and immune cells. Chest, ear and sinus infections come back again and again, and may be slow to clear.
Sensitivity to radiation
X-rays, CT scans and radiotherapy cause far more DNA damage in these children than in others. That damage can itself lead to cancer later, so doctors choose scans carefully.
A high risk of lymphoma
Lymphoma, a cancer of the immune system, is the main cancer seen, often before adult life. Brain tumours and some other childhood cancers have also been reported.
In girls
- The ovaries often stop working early
- Puberty may need hormone support
Not sure whether this applies to you?
Ask an oncologistReaching a diagnosis
How is the syndrome confirmed?
-
A doctor notices a pattern
A small head size together with repeated infections, or an unexpected reaction to treatment, makes a paediatrician suspect a DNA repair condition.
-
Blood tests look at immunity
Antibody levels and immune cell counts show whether the immune system is affected. These results also guide day-to-day care.
-
A genetic test looks at NBN
A blood sample is tested for faults in NBN, often on a panel that also checks similar repair genes such as ATM. Finding two faulty copies confirms the diagnosis.
-
Both parents are tested
This checks that each parent carries one of the two faults. It confirms the result and tells the parents about their own carrier status.
-
Brothers and sisters are considered
Each brother or sister of an affected child has a one in four chance of also having the syndrome. Testing them early means care can start before problems appear.
Words you will hear
What do the doctors' terms mean?
- Biallelic
- Both copies of the gene are faulty. This is what causes the syndrome.
- Autosomal recessive
- An inheritance pattern where the condition appears only when a child receives a faulty copy from both parents.
- Microcephaly
- A head size smaller than expected for the child's age. It is one of the earliest signs.
- Immunodeficiency
- A weak immune system that struggles to fight infection. It varies from mild to severe.
- Immunoglobulin replacement
- Regular infusions of donated antibodies, given to children whose own antibody levels are too low.
- Chromosome instability
- Breaks and rearrangements seen when the child's chromosomes are looked at under a microscope. It was how the syndrome was first recognised.
Leave a number, we will call you
One field. No form to fill in, and no charge for the call.
How care changes
How is care different for a child with the syndrome?
Usual approach
With Nijmegen breakage syndrome
X-rays and CT scans when needed
MRI and ultrasound preferred wherever possible
Infections treated as they come
Antibody replacement and early treatment of infection
Cancer treatment at standard strength
Chemotherapy adjusted, and radiotherapy avoided or reduced
Routine childhood check-ups
A regular watch for signs of lymphoma
Vaccines on the usual schedule
The immunity team advises which vaccines are safe
Being straight with you
What can this page not tell you?
It cannot tell you whether your child has the syndrome. A small head or frequent colds have many common, harmless causes. Only a specialist examination and a genetic test can answer the question. What your specific variant means is a question for the counsellor who ordered the test.
It cannot predict how your child will do
Children with the syndrome differ widely. Some have milder immune problems, and not every child develops cancer. The long-term outlook depends on the immune system, on whether lymphoma appears, and on the care available. Studies so far come mostly from European families.
Who this does not apply to
This page is about children with two faulty NBN copies. If you are an adult told you carry one faulty copy, you do not have the syndrome and none of these features will appear in you. Your situation is covered on the NBN carrier pages. Tests on a tumour are a separate matter, covered under targeted therapy.
Care usually involves a paediatric immunologist, a paediatric oncologist and a clinical geneticist working together.Commonly believed
What do families believe about the syndrome that is not true?
"Something in the pregnancy caused this."
The syndrome comes from the genes each parent passed on. Food, medicines, work or worry during the pregnancy did not cause it, and nothing the mother did could have changed it.
"Our next child will be fine, because it already happened once."
Chance has no memory. Each pregnancy between the same two carrier parents carries the same one in four chance, whatever happened before.
"Avoiding scans means missing a cancer."
MRI and ultrasound use no radiation and can answer most questions. Doctors still use X-rays when truly needed, but they choose them carefully and keep them few.
"As carriers, we parents are also at serious risk."
Parents carry one faulty copy each. Their own cancer risk is modest at most, and nothing like their child's. It is still worth each parent speaking to a counsellor.
Questions we are asked
Common questions about Nijmegen breakage syndrome
Can Nijmegen breakage syndrome be treated?
The gene fault cannot be corrected, but much of the illness can be managed. Antibody replacement reduces infections. Careful choice of scans limits radiation. Lymphoma is treated with adjusted doses. In some centres, a bone marrow transplant has been tried, though experience is still limited.
Is lymphoma certain for a child with the syndrome?
No, but the risk is high, and it often appears in childhood or the teenage years. That is why children are watched closely for swollen glands, fevers and weight loss. Lymphoma found early is easier to treat, even with the dose changes these children need.
Is it the same as ataxia-telangiectasia?
They are related but different. Both involve faults in the same repair pathway, and both cause weak immunity, radiation sensitivity and lymphoma. Ataxia-telangiectasia comes from the ATM gene and causes problems with balance. Nijmegen breakage syndrome causes a small head size instead.
Can the next pregnancy be tested?
Yes, once the exact faults in both parents are known. Testing can be done early in a pregnancy, or on embryos during IVF. It is best discussed with a genetic counsellor before the next pregnancy begins, so there is time to decide calmly.
Should our other children be tested?
Brothers and sisters of an affected child should be offered testing, even if they seem well. Knowing early allows immune checks and safer scan choices from the start. Healthy siblings may still be carriers, which matters later for their own families.
Does marrying within the family matter?
Yes. Related partners are more likely to carry the same rare fault from a shared ancestor. Cousin and uncle-niece marriages are common in parts of Telangana. If other couples in the family plan children, they can ask about carrier testing first.
Can my child go to school normally?
Many children do, with some extra support. Learning may slow as they grow, so school support helps. Infections spread easily in classrooms, and your child's immunity team will advise on precautions and on when to stay home.
Who should we see first?
A paediatrician who can refer you to a clinical geneticist and a paediatric immunologist. If your child has already had lymphoma or cancer, the treating oncologist should know about the syndrome. Call the CION helpline if you are unsure where to start in Hyderabad.
Your Specialists
Meet CION's oncologists. Bring your family history or genetic report to them.
Our medical oncologists see people with a strong family history of cancer, arrange genetic counselling and testing where it fits, and plan the checks that follow.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
Medical Oncologist
Medical Oncologist
Want a specific doctor for your case? Mention them when booking.
Book Free ConsultationBook an appointment with our specialist
Share your name and number — we'll call you back within 30 minutes to schedule your consultation.
Sources
- GeneReviews (NCBI) — Nijmegen Breakage Syndrome
- MedlinePlus Genetics — Nijmegen breakage syndrome
- MedlinePlus Genetics — NBN gene
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
The NBN gene: what it doesHow the repair gene works when it is healthyTesting the family for NBNSiblings, parents and partners: who to test and whenBiallelic ATM and ataxia-telangiectasiaThe closely related condition from the partner geneNBN mutation: which cancers and what riskWhat one faulty copy means for the parents
Talk to us
Worried a child in your family may have this?
Tell us what doctors have noticed so far and who in the family has been tested. We will help you reach the right paediatric and genetics specialists. One helpline serves every CION centre.