Medical Oncologist
CION Cancer Clinics
Testing the family for BLM, WRN and RECQL4 faults | CION Cancer Clinics
These three genes cause illness only when a person inherits a faulty copy from both parents. So testing the family is about two things: finding brothers or sisters who may have the syndrome but have not been diagnosed, and telling carriers apart so they can plan their own families. This page explains who to test, in what order, and what each result means. 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 after a diagnosis?
- What does testing mean for each person in the family?
- How does testing move through the family, step by step?
- The words you will meet, in plain language
- What a brother or sister's result means for them
- Four things families tell us, and what is actually true
- What this page cannot tell you
- Common questions about testing the family
The short answer
Who in the family should be tested after a diagnosis?
Start with the parents and the brothers and sisters of the person who has the syndrome. Parents are usually carriers, and a brother or sister could have the same condition without anyone having named it yet.
Why this is different from most gene faults
Bloom, Werner and Rothmund-Thomson syndromes are recessive. A person only has the condition when both copies of the gene are faulty, one from each parent. Someone with one faulty copy is a carrier. Carriers are usually healthy and are not patients.
Two separate reasons to test a relative
The first is to find anyone who has the syndrome itself, because they need the same cancer watching and care as the person already diagnosed. This mostly means brothers and sisters. The second is to find carriers, so they can plan their own families with the facts in hand. This means parents, adult siblings, and sometimes cousins and partners.
The laboratory looks only for the exact faults already found in your family. That makes each relative's test simpler than the first one.Relative by relative
What does testing mean for each person in the family?
Each relative is asking a different question. The counsellor will explain which one applies to whom.
Parents
In most families each parent carries one faulty copy. Testing them confirms that the two faults in the child came from different parents, which firms up the diagnosis. It also tells the couple what to expect in a future pregnancy.
Brothers and sisters
These are the relatives most likely to have the syndrome as well. A sibling can be affected even if they look well today, especially with Werner syndrome, where signs appear in young adult life.
A sibling may be
- Affected, with two faulty copies
- A carrier, with one faulty copy
- Clear, with two working copies
Aunts, uncles and cousins
They are very unlikely to have the syndrome, but some may be carriers. This matters most when marriages within the family are common, because two carriers can then meet.
A partner planning children
When a known carrier plans a family, the partner can be tested for faults in the same gene. It is most useful when the couple are related by blood.
Not sure whether this applies to you?
Ask an oncologistThe usual order
How does testing move through the family, step by step?
-
Confirm the diagnosis in the person who has the syndrome
The report should name two faults in one of the three genes. Without that, relatives have nothing specific to be tested for.
-
Test both parents
This shows whether each parent carries one of the two faults. Now and then a fault turns out to be new in the child, which changes the advice for the rest of the family.
-
Test brothers and sisters for the syndrome itself
A sibling with signs, or an adult sibling of someone with Werner syndrome, is usually offered a test sooner rather than later. Finding the condition early means cancer watching can start.
-
Offer carrier testing to adult relatives who want it
This is a personal choice, usually made around marriage or before a pregnancy. Nobody has to be tested, and some relatives prefer not to know.
-
Plan future pregnancies with a counsellor
Once both faults are known, a carrier couple can discuss testing in pregnancy or testing embryos during IVF. They can also choose neither. Both options exist in India.
On your report
The words you will meet, in plain language
- Recessive
- A condition that appears only when both copies of a gene are faulty. One working copy is usually enough to stay well.
- Biallelic
- Both copies of the gene carry a fault. This is the result that means a person has the syndrome itself.
- Carrier
- Someone with one faulty copy and one working copy. A carrier usually has no signs of the syndrome.
- Obligate carrier
- A relative who must carry the fault because of how the family is connected, such as the parent of an affected child.
- Cascade testing
- Testing relatives one circle at a time, starting nearest to the person diagnosed and moving outwards.
- Targeted test
- A test that looks only for a fault already found in the family. It is simpler than the first test and usually costs less.
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Side by side
What a brother or sister's result means for them
Two faulty copies
One faulty copy, or none
They have the syndrome, even if signs are mild so far
They do not have the syndrome
A cancer watching plan is made for them
Screening is usually the same as for anyone else
Doctors may take care with X-rays and some cancer medicines
No change to medical care is usually needed
Their own children will be carriers at the least
A carrier can pass the fault on, which matters for their own family plans
Commonly believed
Four things families tell us, and what is actually true
"We are carriers, so we will get cancer too."
Carriers of these three genes are usually healthy. For BLM, studies on whether one faulty copy slightly raises cancer risk have given mixed answers. Carriers are not usually offered extra screening on this basis alone.
"Our other children look fine, so they cannot have it."
Signs can be mild or slow to show. Werner syndrome often looks like nothing until young adult life. A test answers the question more reliably than appearance.
"The mother's side must be to blame."
A recessive syndrome needs a faulty copy from both parents. Neither side is responsible, and neither parent could have known. Blame does real damage in families and has no basis in the science.
"If we test our young children now, we can plan their marriages early."
Carrier testing is usually left until a child is old enough to decide for themselves. Testing a young child is done when signs suggest the syndrome itself, because that result changes their care today.
Being straight with you
What this page cannot tell you
It cannot tell you which of your relatives carries the fault. Only a test can, and the test only works once the exact faults in your family are known. A genetic counsellor draws out the family tree and works out who should be offered testing first.
It cannot read your report
These are rare conditions, and faults in the same gene can behave differently. What your specific variant means is a question for the counsellor who ordered the test. Please bring the report rather than searching for the variant online.
Who this does not apply to
Most people reading about these genes do not need a test. If nobody in your family has Bloom, Werner or Rothmund-Thomson syndrome, and nobody has been found to carry a fault, family testing is not relevant to you. Counselling can take place in Telugu, and a family letter can be written for relatives in other districts.
If you are unsure where to begin, call the helpline. Someone will help you reach a genetics team.Questions we are asked
Common questions about testing the family
What is the chance that our next child will have the syndrome?
When both parents are carriers, each pregnancy has a one in four chance of a child with the syndrome. There is a one in two chance of a carrier child and a one in four chance of a child with two working copies. The chance is the same in every pregnancy, whatever happened before.
Should my other children be tested now?
If a child has any signs, or is an adult sibling of someone with Werner syndrome, testing for the syndrome itself is usually worthwhile. Testing only to find out whether a young child is a carrier usually waits until they can choose. Your counsellor will help you decide.
I am a carrier. Do I need regular scans?
Usually not for the carrier result alone. Most carriers follow the same screening advice as anyone else of their age and background. If your family also has other cancers, your counsellor may suggest checks based on that history instead.
My partner and I are cousins. Should we both be tested?
If a fault is already known in the family, it is sensible for both of you to be tested for it before a pregnancy. Being related raises the chance that you both carry the same fault. A counsellor can explain what each result would mean for your children.
What if the person who had the syndrome has died?
Their earlier report may still be on file, so ask the hospital that treated them. If there is no report, stored tissue from an old biopsy or surgery can sometimes be tested. Testing both parents can also help rebuild the picture.
Do relatives in another state need to come to Hyderabad?
Not always. Once the family fault is known, a relative can often give a blood sample near home and have it sent to a laboratory. They will need a copy of the original report so the right fault is checked.
Can a carrier result affect a marriage proposal?
Families worry about this, and it is a fair question. Being a carrier is common for recessive faults and says nothing about a person's own health. What you share and when is your choice. A counsellor can help you think about how to explain it.
Who pays for relatives to be tested?
Usually the family, because insurance rarely covers testing of a healthy relative. A targeted test for a known fault costs less than the first test. Ask the counsellor for a written estimate before any sample is taken.
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) — Bloom Syndrome
- GeneReviews (NCBI) — Werner Syndrome
- GeneReviews (NCBI) — Rothmund-Thomson Syndrome
- MedlinePlus Genetics — What are the different ways a genetic condition can be inherited?
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
BLM, WRN and RECQL4 positive: what happens nextThe plan for the person who has the syndromeBLM, WRN and RECQL4: which cancers and what riskWhat an affected sibling would be watched forConsanguineous families and testingWhy marriages within the family change the carrier pictureHow cascade testing worksTesting relatives one circle at a time
Talk to us
Not sure which relatives should be tested?
Tell us who in the family has been diagnosed and what the report says. We will help you reach a genetics team who can plan testing for the rest of the family. One helpline serves every CION centre.