Neurofibromatosis type 1 (NF1)
NF1 is a condition you are born with, caused by a gene that normally keeps the growth of nerve sheath cells in check and no longer does its job.
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NF1 is a condition you are born with, caused by a gene that normally keeps the growth of nerve sheath cells in check and no longer does its job. As a result, benign lumps form along the nerves and in the skin, and light brown patches appear on the skin. The gene has been there since birth, so the cause itself cannot be removed. What the condition looks like, though, varies enormously: one person knows about the diagnosis only from a few skin patches, another needs surgery, an orthopaedic surgeon and lifelong monitoring. There is a similarly named but genuinely different condition, neurofibromatosis type 2; the two have little in common beyond the word in the name.
What shows up on the skin
The skin changes earliest in NF1, and it is usually what brings people to a doctor in the first place.
- Café-au-lait patches. Flat, light brown, with clear edges. They appear in the first or second year of life and grow along with the child. Six or more patches larger than 5 mm in a child (larger than 15 mm after puberty begins) are the commonest reason to suspect NF1. On brown and black skin they are harder to make out, so look in daylight rather than in a dim room.
- Freckling where skin rubs against skin: armpits, groin, under the breasts, in the buttock crease. It usually appears by the age of three to five. Sun freckles on the face and arms do not count — what matters is that the area is normally covered.
- Neurofibromas — soft lumps in the skin or just under it, anywhere from the size of a match head to a cherry. They tend to start in the teenage years and become more numerous with time. They can itch or ache when pressed. They are not dangerous in themselves, but when there are many of them they weigh heavily on how a person feels about their own appearance.
- Plexiform neurofibromas grow not as a single lump but along a whole nerve trunk. They are often noticed in infancy: an uneven thickening under the skin, sometimes with darker, hairier skin over it. These are the ones that cause deformity of the face and limbs, and the ones watched most closely.
What happens beyond the skin
NF1 involves more than the skin, and some of it is not something a person can spot in themselves — it is picked up at a routine check.
- Eyes. Tiny yellow-brown bumps can appear on the iris (Lisch nodules). They are harmless and do not affect sight, but a doctor sees them with a slit lamp and uses them as a sign of the condition. A separate matter is optic pathway glioma: a slow-growing tumour, most often in preschool children, which can reduce vision without the child noticing.
- Bones. Infants may have bowing of the lower leg and a false joint, where a bone fails to knit after a fracture. Scoliosis can develop during the school years. Less often the wall of the eye socket is underdeveloped and the eye bulges forwards.
- Height and head size. Head circumference is usually above average and height below it. On its own this is not an illness and needs no treatment.
- Learning and attention. Many children have difficulty with reading, writing, arithmetic, coordination and holding attention. Intelligence is usually normal, and what makes the difference is not extra drilling but support arranged at school early enough.
- Blood pressure. In NF1 raised blood pressure occurs even in children, and it is not something to put down to age — it needs measuring and the cause needs finding.
How the diagnosis is made
NF1 is a clinical diagnosis: it is assembled from a combination of signs rather than from a single test. That is why the examination has to be a thorough one, not a glance at an arm.
- Examination of the whole skin in good light, armpits, groin and skin folds included — leave them out and the most characteristic sign is missed.
- An eye assessment: slit lamp for the iris, plus tests of visual acuity, visual fields and colour vision. In a small child, checking vision matters more than hunting for nodules, because optic pathway glioma announces itself as loss of vision.
- MRI of the brain, orbits, spine or whichever area is relevant — not routinely and just in case, but when there are symptoms, reduced vision, neurological signs or a suspicious lump.
- Genetic testing to look for the change in the NF1 gene. It is useful when there are still few signs, when the child is very young, when a family is planning children, or when a mosaic form is suspected.
In a child under two or three the signs have often not accumulated yet: there are patches and nothing else. In that situation the diagnosis is neither ruled out nor confirmed — a repeat examination is arranged a few months later.
Signs that should not wait
The most serious risk in NF1 is a plexiform neurofibroma turning into a malignant peripheral nerve sheath tumour. It affects a minority of people, but the outcome depends heavily on how quickly it is found. See a doctor the same day, or within a few days, if a lump has changed:
- it has started growing noticeably faster;
- it hurts constantly, including at night and without being touched;
- it has become firm and hard and no longer moves under the skin;
- weakness, numbness or loss of sensation has appeared in the area supplied by that nerve.
Call an ambulance straight away — in Spain, Italy, Portugal, Poland and Ukraine on the single European number 112 — if:
- a first-ever seizure occurs;
- vision is suddenly lost in one eye;
- an arm or leg suddenly becomes weak, or speech becomes slurred;
- a severe headache comes with vomiting and increasing drowsiness.
A same-day appointment is needed if a child's vision has worsened or a squint has appeared, if blood pressure stays high, or if a curve of the spine is visibly getting worse.
What can be done
There is no treatment that removes the altered gene. What is treated is whatever is already causing trouble, while trying not to create new problems.
- Watching rather than operating. A quiet lump that neither grows nor hurts is best left alone: surgery leaves a scar and changes nothing.
- Surgery. Skin neurofibromas are removed when they catch on clothing, bleed, or are a clear burden. Plexiform ones are operated on cautiously: they grow through the nerve itself and cannot always be removed completely.
- Targeted medicines. For large plexiform neurofibromas in children that cannot be operated on, medicines from the MEK inhibitor group are used. They are taken by mouth and can shrink the tumour. They have their own side effects — rash, bowel upset, nail changes, effects on the heart and eyes — so treatment runs with regular monitoring.
- Orthopaedic care for scoliosis and bowing of the lower leg, up to and including surgery.
- Care of the eyes: glasses, early treatment of a lazy eye, and monitoring or treatment of optic pathway glioma.
- Pain relief. Where a burning pain follows the line of a nerve, ordinary painkillers work poorly and a doctor will choose medicines aimed at nerve pain instead.
A word about radiotherapy: in NF1 it is used sparingly. In someone with an altered NF1 gene, an irradiated area later produces more new tumours than it would in anyone else, so the decision is made by a team rather than a single doctor, and only when there is no other way.
Monitoring, year by year
Monitoring in NF1 is not a formality. It is designed to catch changes before the person notices them.
- A full review at least once a year: the whole skin, new or altered lumps, the spine, height and weight in a child, development and progress at school.
- Vision checked annually in children; in adults as often as the eye specialist advises.
- Blood pressure measured every year, children included. Persistently high readings are a reason to look for narrowing of a kidney artery or a rare adrenal tumour (phaeochromocytoma), not simply to prescribe tablets.
- Attention to the breasts in women: in NF1 breast cancer is more common and occurs at a younger age, so screening starts earlier than usual and sometimes includes MRI. The starting age and the method follow your own country's rules, so discuss it with a doctor in advance rather than waiting for the general schedule.
- A simple rule at home: any new lump, or one that has changed, is shown to a doctor without waiting for the next scheduled appointment.
Genes, family and pregnancy
NF1 is caused by a change in a single gene and is passed on in a dominant pattern: inheriting it from one parent is enough. The chance of passing it to each child is one in two, 50 % in every pregnancy, whatever happened with previous children.
In roughly half of people with NF1 the parents are unaffected: the change arose afresh as the egg or sperm was formed. It has nothing to do with the parents' way of life, with medicines, or with anything that happened during the pregnancy.
There is also a mosaic, or segmental, form: the change appeared after conception and the signs are confined to one area of the body. It tends to be milder, but it is still worth confirming with a geneticist, not least because the risk to children is different.
Severity itself is not inherited: a parent with a few patches can have a child with marked problems, and the other way round. If you are planning a family, a genetics appointment offers far more than searching online; prenatal and preimplantation testing are discussed there too.
During pregnancy neurofibromas often enlarge and become itchy, and blood pressure may rise. This is not a complication to be frightened of, but the obstetric team should know the diagnosis from the start: in NF1 blood pressure and the state of the arteries are watched more closely than usual.
Online consultation
NF1 is the kind of condition where half the questions come up between appointments: has that patch changed, is this lump worth showing, which specialist to see first, what a sentence in the MRI report actually means. In an online consultation a doctor can go through your situation, help turn the monitoring into a plan that makes sense, and point you to the right person — eye specialist, orthopaedic surgeon, neurologist or geneticist.
It is a convenient way to go over test results and to work out what needs an urgent visit and what can wait for the routine review. If any of the signs in the urgent section are present, though, the place to start is emergency care, not an online appointment.
This material is for information only and does not replace medical advice.
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