Medical Oncologist
CION Cancer Clinics
Testing relatives for NF2, SMARCB1 and LZTR1 faults | CION Cancer Clinics
Once a fault in NF2, SMARCB1 or LZTR1 is found in one person, close relatives can be tested for that exact fault. For NF2, children are usually tested early, because checks start in childhood. For SMARCB1 and LZTR1, many carriers never develop tumours, so testing is less urgent. This page explains who is offered a test, in what order, and what each result changes. At CION Cancer Clinics, our oncologists explain what a gene result means for you and your family, and plan the checks that follow.
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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
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On this page
- Who in the family should be tested for NF2 or schwannomatosis genes?
- Which relatives are offered a test, and why?
- How does family testing work, step by step?
- The words you will meet, in plain language
- What a relative's result changes, and what it does not
- What this page cannot tell you
- Four things families tell us about testing relatives
- Common questions about testing the family
The short answer
Who in the family should be tested for NF2 or schwannomatosis genes?
Start with the person who already has the tumours. Once their exact fault is found, their children, brothers, sisters and parents can be offered a simple blood test for that one fault. For NF2, children are usually tested early, because their checks would begin in childhood.
Why NF2 is tested in childhood when most genes are not
For most adult cancer genes, testing waits until the child is old enough to decide. NF2 is one of the exceptions. Tumours can start in the teenage years or earlier, and hearing checks and scans genuinely help. A child who tests negative is also spared years of scans they never needed.
Why SMARCB1 and LZTR1 are handled differently
These two genes cause schwannomatosis, where tumours grow on nerves elsewhere in the body. Many people who carry a fault in them never develop a tumour at all. Checks, where they are offered, usually begin in adult life. So testing a well child is rarely urgent, and the decision can often wait until they can make it themselves.
A relative's test is only as useful as the first result. The exact family fault has to be known before anyone else is tested.Relative by relative
Which relatives are offered a test, and why?
These genes follow the same basic rule. Each child of a person who carries the fault has a one in two chance of inheriting it.
Children of a person with NF2
Offered testing early in childhood. A positive result starts hearing, eye and scan checks at the right time. A negative result ends the worry for that child and for their future children.
Parents
Tested to learn where the fault came from. In NF2, about half of people have no affected parent, because the fault arose new in them. Knowing this tells the wider family whether they need testing at all.
Brothers and sisters
Offered testing if a parent carries the fault. If neither parent does, brothers and sisters are usually at very low risk, and scans are not needed for them.
Relatives of a SMARCB1 or LZTR1 carrier
Adults can choose a test. Many who carry the fault stay well, so the result guides checks rather than predicting tumours.
Worth asking about
- Whether pain or lumps in the family point to schwannomatosis
- Whether children need testing now or later
- How the result changes family planning
Not sure whether this applies to you?
Ask an oncologistIn order
How does family testing work, step by step?
Find the fault in the affected person
A blood test from the person with tumours looks for the fault. If it is found, the family now has something exact to test for.
If the blood shows nothing, test the tumours
In NF2 the fault can sit in only some of the body's cells. Testing tissue from two separate tumours can find a fault the blood missed. The same approach is used in schwannomatosis.
Counselling before each relative's test
Every relative has their own conversation first, about what a positive or negative result would mean for them. Nobody should be tested because a family elder decided on their behalf.
The relative's result and what follows
A positive result leads to a surveillance plan for that gene. A negative result for the known family fault usually means no special checks are needed.
On the family letter
The words you will meet, in plain language
- Dominant
- One faulty copy of the gene is enough to raise risk. It can pass from a mother or a father, to a son or a daughter.
- De novo
- A fault that appeared for the first time in one person. Their parents do not carry it, but their children can inherit it.
- Mosaic
- The fault is present in some cells of the body but not all. It can be missed by a blood test and is common in people who are the first in their family with NF2.
- Predictive test
- A test for the known family fault in a relative who has no tumours. It answers one question: did this person inherit it?
- Penetrance
- How often a fault actually leads to tumours. It is high for NF2 and much lower for SMARCB1 and especially LZTR1.
- Cascade testing
- Offering the test outward through a family, one set of close relatives at a time.
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Side by side
What a relative's result changes, and what it does not
The relative tests positive
The relative tests negative
A surveillance plan for that gene begins
No special checks for this fault are needed
Their own children can be offered a test
Their children are not at raised risk from it
Family planning options can be discussed
No special family planning is needed
Symptoms are taken seriously sooner
Symptoms are assessed in the usual way
Being straight with you
What this page cannot tell you
It cannot tell you which relatives in your family should be tested, or in what order. That depends on who has tumours, who has been tested and whether a fault was found at all. A genetic counsellor works it out from your family tree.
It cannot read your result
A report may name a gene and a variant, or say that no fault was found in blood. Both need careful reading. A negative blood result in someone with clear NF2 does not rule it out, because of mosaicism. What your specific variant means is a question for the counsellor who ordered the test.
Who this does not apply to
Relatives of someone with a single tumour on one hearing nerve, found in later life, usually do not need testing. Most such tumours are one-off growths. The same is true when nobody in the family has tumours and a fault turned up by chance on a wider test.
Relatives in a district or another state can often give a sample locally. Ask the counsellor how the sample can reach the right laboratory.Commonly believed
Four things families tell us about testing relatives
"Nobody before him had NF2, so his children are safe."
Many people with NF2 are the first in their family. Their children still have a chance of inheriting it. A child who inherits it from a mosaic parent carries the fault in every cell.
"We should wait until the child is older to test."
That is the right advice for most adult cancer genes. NF2 is different, because checks start in childhood and help. Testing early means a negative child can skip scans entirely.
"A positive LZTR1 test means my daughter will get tumours."
Many LZTR1 carriers never develop a tumour. The result guides sensible checks if symptoms appear. It does not predict what will happen to her.
"If we talk about this, no family will agree to a marriage."
This fear is real and common. A counsellor can help you decide what to share, with whom and when. Many families find a calm, factual explanation lands far better than they feared.
Questions we are asked
Common questions about testing the family
What is the chance my child has inherited NF2?
If a parent carries the fault in every cell, each child has a one in two chance of inheriting it, whether the child is a boy or a girl. If the parent is mosaic, the chance is lower. A counsellor can explain what applies to your family and arrange the child's test.
At what age can a child be tested for NF2?
Children of a known carrier are usually offered testing in early childhood, sometimes soon after birth. The aim is to have the answer before checks would begin. Only a small blood sample is needed. Your counsellor will talk through timing that suits your child.
My blood test was negative, but I have NF2. Can my family still be tested?
Possibly. Your fault may be present only in some cells. Testing two of your tumours, from stored surgery tissue, can find it. Once it is found, your children can be tested for that exact fault. Ask your team whether your old tissue blocks are still stored.
Should brothers and sisters be tested if our parents are well?
It depends on the parents. If neither parent carries the fault, brothers and sisters are at very low risk. If a parent has not been tested, or has signs such as hearing loss in one ear, testing brothers and sisters is usually worthwhile. A counsellor sorts this out from your family tree.
Is a SMARCB1 fault the same as the one that causes rhabdoid tumours?
It is the same gene, but usually a different kind of fault. One kind leads to schwannomatosis in adults. Another leads to rhabdoid tumours in young children, which is handled very differently. Your laboratory report and counsellor will say which one applies to your family.
Can we have a child without passing this on?
There are options, including testing embryos during IVF and testing during pregnancy. Each carries its own costs, rules and personal questions. Talk it through with a counsellor before pregnancy if you can. There is no right choice, only the one that fits your family.
Does marrying within the family change the risk?
For these dominant genes, a child's chance comes from the parent who carries the fault. Marrying a relative does not raise it. It can matter for other, recessive conditions, so mention it when you meet the counsellor. They will ask about it anyway.
Can counselling for the family happen in Telugu?
Yes. The conversation about who to test, and what a result means, should happen in the language each relative is most comfortable in. Ask for Telugu when you book. Bring older relatives who may know the family history better than anyone else.
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
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Sources
- GeneReviews (NCBI Bookshelf) — NF2-Related Schwannomatosis
- MedlinePlus Genetics — Schwannomatosis
- MedlinePlus Genetics — What are the different ways a genetic condition can be inherited?
- National Cancer Institute — Genetic Testing for Inherited Cancer Susceptibility Syndromes
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
Surveillance for NF2 and schwannomatosis gene carriersWhat checks begin once a relative tests positiveWhat the NF2 and schwannomatosis genes doThe genes themselves, explained plainlyWhich syndromes do require childhood testingWhy NF2 is one of the exceptionsMosaicism explainedHow a fault can be missed by a blood test
Talk to us
Not sure which relatives should be tested first?
Tell us who in the family has tumours and who has been tested. We will help you plan the order of testing and arrange counselling in Telugu or English. One helpline serves every CION centre.