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ALK and PHOX2B: what these genes do and why they matter | CION Cancer Clinics
ALK and PHOX2B are genes that help build the nervous system before a baby is born. ALK tells young nerve cells when to grow, and PHOX2B guides them as they mature. An inherited fault in either gene can raise the chance of neuroblastoma in early childhood. This page explains what the genes do, how a fault leads to a tumour, and why many carriers stay well. 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
- What do the ALK and PHOX2B genes actually do?
- Which conditions are linked to these genes?
- How does a fault in these genes lead to neuroblastoma?
- The words you will meet, in plain language
- How are ALK and PHOX2B different?
- What families often get wrong about these genes
- What this page cannot tell you
- Common questions about the ALK and PHOX2B genes
The short answer
What do the ALK and PHOX2B genes actually do?
Both genes help build the nervous system before a baby is born. ALK works like a switch that tells young nerve cells when to grow. PHOX2B guides those cells as they mature into the nerves that run breathing, heartbeat and digestion without our thinking about it.
ALK, a switch for growth
ALK sits on the surface of developing nerve cells. When a signal arrives, the switch turns on and the cell divides. When the signal stops, the switch turns off. An inherited fault can jam the switch in the on position, so the cell keeps getting a message to grow.
PHOX2B, a guide for maturing cells
PHOX2B works inside the cell. It turns on the set of genes a young nerve cell needs to become a mature one. A fault can leave some cells stuck at an immature stage, where they are more likely to keep dividing.
Why the effect shows up in babies
These genes do most of their work before birth and in the first years of life, while the nervous system is still being built. That is why inherited neuroblastoma is a disease of infants and young children, and why the risk falls as a child grows.
Linked conditions
Which conditions are linked to these genes?
An inherited fault in ALK or PHOX2B is linked to a small group of conditions. Most people with these conditions have only one of them.
Familial neuroblastoma
A tumour of immature nerve cells that runs in a family. Most inherited cases involve ALK. A smaller share involve PHOX2B. Inherited cases are often found in the first year of life, and a child may have more than one tumour at once.
Breathing-control problems
PHOX2B faults can cause congenital central hypoventilation syndrome, or CCHS. The body does not breathe deeply enough during sleep and may need support at night.
Hirschsprung disease
A bowel condition present at birth, where nerve cells are missing from part of the gut. It can occur with PHOX2B faults, sometimes alongside CCHS.
Often first noticed as
- Severe constipation from birth
- A swollen tummy in a newborn
ALK in other cancers
ALK changes also appear in some lung cancers and lymphomas. These arise in the tumour alone and are not inherited. They belong to targeted therapy, not this page.
Not sure whether this applies to you?
Ask an oncologistHow a fault turns into a tumour
How does a fault in these genes lead to neuroblastoma?
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Young nerve cells form before birth
Early in pregnancy, a group of cells travels through the growing baby and settles in places like the adrenal glands and along the spine.
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Normally, they mature and stop dividing
Guided by genes like PHOX2B, most of these cells grow up into working nerve cells. Once mature, they stop dividing.
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A fault upsets that balance
A jammed ALK switch keeps telling cells to grow. A faulty PHOX2B can stop them maturing. Either way, some cells stay young and busy for longer than they should.
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A second change tips a cell over
Most of these cells still mature or die away. Occasionally one picks up further changes and begins to grow unchecked, forming a tumour.
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Which is why risk is not certainty
Many children and adults carry the fault and never develop a tumour. Chance plays a large part in whether that second step happens.
On your report
The words you will meet, in plain language
- Receptor
- A switch on the surface of a cell that responds to signals from outside.
- Kinase
- A protein that passes a message along inside the cell. ALK is one.
- Neural crest
- The group of young cells in the unborn baby that becomes many nerves, and from which neuroblastoma arises.
- Autonomic nervous system
- The nerves that run breathing, heartbeat and digestion automatically.
- Gain of function
- A fault that makes a gene work too hard, rather than stop working. Most inherited ALK faults are this kind.
- Germline
- Present in every cell from birth and able to be passed on. A change found only in the tumour is called somatic.
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Side by side
How are ALK and PHOX2B different?
ALK
PHOX2B
A growth switch on the cell surface
A guide inside the cell that drives maturing
The commonest cause of inherited neuroblastoma
A rarer cause of inherited neuroblastoma
Usually no other health problems
Often with breathing or bowel problems
Medicines that block ALK exist for tumours
No medicine yet targets PHOX2B directly
Commonly believed
What families often get wrong about these genes
"ALK in my father's lung cancer means our children are at risk."
ALK changes in lung cancer arise in the tumour alone. They are not inherited and do not pass to children.
"A faulty gene means something is broken in my child right now."
A carrier child is usually completely healthy. The fault only raises the chance that a tumour will form, mostly in the early years.
"You need two faulty copies for it to matter."
Not for these genes. One inherited faulty copy is enough to raise the risk, which is why it can pass from one parent.
"If PHOX2B is involved, the child will always have a tumour."
Many PHOX2B changes mainly affect breathing, and the tumour risk depends on the exact change. Some children never develop one.
Being straight with you
What this page cannot tell you
It cannot tell you whether a gene change in your family is harmful. The same gene can carry harmless spelling differences and serious faults side by side. What your specific variant means is a question for the counsellor who ordered the test.
It cannot predict one child's future
Studies of these genes are small, because so few families carry them. Doctors can describe the pattern across families, but not what will happen to your child. Chance plays a large part. Two brothers can carry the same fault, and one may develop a tumour while the other never does. Nothing the family does or avoids is known to change that.
It cannot replace the tumour report
Treatment decisions for a child who already has neuroblastoma rest on the tumour itself: its stage, its behaviour and the changes found inside it. Your child's oncologist reads that report alongside any inherited result.
Who this does not apply to
Most children with neuroblastoma have no inherited fault in either gene, and most families do not need this test. If your child had a single tumour, at the usual age, with no family history and no breathing or bowel problems, an inherited ALK or PHOX2B fault is unlikely. Your oncologist or counsellor can tell you honestly whether testing would add anything.
Questions we are asked
Common questions about the ALK and PHOX2B genes
What does ALK stand for?
Anaplastic lymphoma kinase. It was named after the type of lymphoma where it was first found. The name has little to do with its role in neuroblastoma, which is as a growth switch in developing nerve cells.
Is the ALK in neuroblastoma the same as the ALK in lung cancer?
It is the same gene, but the change is different and so is the setting. In lung cancer, ALK changes arise in the tumour and are not inherited. In familial neuroblastoma, the fault is present from birth and can pass down the family.
How is a child tested for these genes?
With a blood sample, usually after a counselling appointment. The laboratory reads ALK, PHOX2B and sometimes other related genes. Testing is normally done first in the child who had neuroblastoma, then in relatives if a fault is found.
Can a tumour test show an inherited fault?
It can raise the question, but it cannot answer it. Most ALK changes found in a neuroblastoma arose in the tumour alone. A blood test is needed to tell whether the change was present from birth.
Does a PHOX2B fault always cause breathing problems?
No. The effect depends on the exact change. Some changes cause serious breathing problems from birth. Others are milder and are found only because a relative was tested. Your counsellor will explain which kind your family has.
Can these faults be fixed?
An inherited fault cannot be corrected or reversed. What can be done is careful watching in the early years, so that any tumour is found while it is small. Medicines that block ALK are used for tumours, not to change the gene.
Does marrying a relative raise the risk?
Not for these genes. They pass from one parent, so marriage between relatives does not create the fault or make it more likely to be passed on. It matters for other, recessive conditions, which your counsellor can discuss.
Where can we get counselling about these genes?
Ask your child's paediatric oncologist for a referral to a genetic counsellor. Counselling can be done in Telugu. Call the CION helpline if you are unsure where to begin, and someone will guide you to the right clinic.
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)
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Sources
- MedlinePlus Genetics — ALK gene
- MedlinePlus Genetics — PHOX2B gene
- GeneReviews (NCBI) — ALK-Related Neuroblastic Tumor Susceptibility
- MedlinePlus Genetics — Neuroblastoma
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
Familial neuroblastoma: how rare is it?How often neuroblastoma really runs in familiesALK and PHOX2B mutation: which cancers and what riskThe tumours these faults are linked toTesting the family for ALK and PHOX2BWho should be tested, and why young children are tested earlyALK and PHOX2B positive: what happens nextThe checking plan for a carrier child
Talk to us
Has your child's doctor mentioned ALK or PHOX2B?
Tell us what the report says and who in the family has been affected. We will help you find a counsellor who can explain what it means. One helpline serves every CION centre.