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Neurofibromatosis Type 1 (NF1)

What is neurofibromatosis type 1?

Neurofibromatosis type 1 (NF1) (say: noor-oh-fie-broh-muh-TOE-sis) is a genetic disorder that affects the way cells divide in the body. It causes skin changes and may also have other effects.

Symptoms of NF1 range from very mild to quite severe. Complications from NF1 may occur over a person's lifetime, and some may get worse over time. But most people with NF1 will have only mild symptoms that do not need special treatment. Keep this in mind when you read about the possible complications of NF1.

NF1 affects about 1 in every 3000 people.

The most common features of NF1

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The most common features of Neurofibromatosis Type 1 (NF1). It is not likely that a child with NF1 will develop many or all of these features.

Café-au-lait spots

Café-au-lait (say: kah-fay oh LAY) spots are the most common feature of NF1. They usually appear within the first 2 years of life and generally do not increase in number after young childhood. 

Café-au-lait spots are harmless, flat, oval-shaped marks on the skin. Café-au-lait means "coffee with milk" in French. The name refers to the colour of the spots. Their colour is at least a shade darker than the colour of your child's skin.

About 1 in 10 people without NF1 will have 1 or 2 of these birthmarks. But people with NF1 almost always have more than 6 café-au-lait spots. 

There is no relationship between the number of café-au-lait spots your child has and how severe NF1 will be for him.

Skin fold freckling

Freckling or small spots may occur on parts of the skin that are not exposed to sunlight. Common areas for freckles are in the armpit and groin. Freckling happens over time, so very young children with NF1 may not show it.


Neurofibromas are benign, soft tumours that involve cells that surround the nerves. "Benign" means they are not cancerous. There are 2 types of neurofibromas: cutaneous (skin) neurofibromas are small bumps on the surface of the skin; subcutaneous (under the skin) are small lumps under the skin that are often hard.

Neurofibromas develop over time throughout the life span.

Neurofibromas usually do not need to be removed and can be difficult to remove. Removal may be considered in special circumstances. 

Lisch nodules

Lisch nodules are small, benign growths that look like freckles on the coloured part of the eye (the iris). Most often, they cannot be seen except with a special eye exam performed by an eye doctor, using an instrument called a slit-lamp. Lisch nodules are harmless and do not affect a child's vision. But they can help your child's doctor diagnose NF1. 

Less common features of NF1

Developmental difficulties

Developmental difficulties occur in about half of children with NF1. For example:

  • They may have problems with learning, such as reading or math.
  • They may also have problems with their fine or gross motor skills. Fine motor skills are small movements such as moving your fingers. Gross motor skills are large movements such as running or jumping.
  • They may have difficultes with social skills, such as making friends.
  • They may have attention and behavioral difficulties.

Watch your child for any movement or learning problems, speech and language delay, or developmental delay. Intervention should be given early for any difficulties or delays.

Plexiform neurofibromas

Plexiform neurofibromas are benign tumours that involve cells that surround the nerves. They may appear near the surface of the skin or may lie deeper in the body. Sometimes they grow to a large size, but usually do not cause any harm to the child's health. Plexiform neurofibromas usually do not need to be removed and can be difficult to remove. Removal may be considered in special circumstances.

In very rare cases, plexiform neurofibromas may become a cancerous tumor called malignant peripheral nerve shealth tumor.

Optic nerve glioma

The optic nerve is the nerve that connects the back of the eyeball to the brain. When this nerve becomes enlarged, it is called optic nerve glioma. This occurs in about 15% of children with NF1. However, in most cases (85%), an optic nerve glioma will not cause any problems with the child's sight or health and is considered asymptomatic (not causing symptoms).

Most often, symptomatic optic nerve gliomas are identified in the first 6 years of life. Your child should be assessed by an eye doctor every year to look for signs of optic nerve involvement. Parents of young children with NF1 should contact their doctor if they notice problems with their child's vision or bulging of the eyeball.

High blood pressure

People with NF1 are more likely to develop high blood pressure, and this may occur at anytime in their life. People with NF1 should have their blood pressure checked every year by their doctor.

Bowing of long bones

Children with NF1 may have bowing of long bones such as the shinbone (tibia). This bowing is apparent within the first year or two of life. This would require a referral to an Orthopedic Surgeon.

Scoliosis: curving of the spine

If your child has NF1, his doctor should check for curving of the spine (scoliosis) once a year. Until your child reaches adult height, he is at a greater risk for scoliosis. This would require a referral to an Orthopedic Surgeon.

Cancerous tumours

People with NF1 have a slightly higher risk of developing certain cancers, such as soft tissue tumors or certain brain tumours. Pay attention to any signs such as problems with your child's vision, rapid changes in the size or texture of neurofibromas, persistent and continuous pain in neurofibroma, persistent and severe headaches or dizziness. Discuss any concerns with your child's doctor.


Most children with NF1 have a growth rate and pattern similar to their parents. However, some children with NF1 have alterations of their growth rate and pattern leading to rapid gains in height or weight, or slowing of the growth leading to shortness. Children with NF1 should have their growth monitored regularly.

Other complications of NF1

Other less common complications of NF1 include:

  • seizures
  • increased fluid surrounding the brain (hydrocephalus)
  • early (precocious) puberty
  • narrowing of the artery that supplies blood to the kidney (renal artery stenosis)
  • congenital heart defects
  • narrowing of an artery in the brain (Moyamoya disease)

Ask your doctor if you have any specific concerns about your child.

Key points

  • Neurofibromatosis type 1 (NF1) is a genetic disorder.
  • The most common features are café-au-lait spots, freckling and neurofibromas.
  • Most children with NF1 will have only mild symptoms.
  • Children should be monitored regularly for possible health complications.

Elena Pope, MD, MSc, FRCPC

Patricia Parkin, MD, FRCPC

Stephen Meyn, MD, PhD, FRCPC, FACMG

Andrea Shugar, MS, CGC, CCGC