Diagnosing neurofibromatosis

Neurofibromatosis type 1 (NF1) is usually diagnosed by checking for the characteristic symptoms of the condition, such as coffee-coloured skin patches (café au lait spots) and bumps on or under the skin (neurofibromas).

A confident diagnosis can usually be made if two or more of the following symptoms are present:

• six or more café-au-lait spots that are larger than 5mm in children or 15mm in adults
• freckles under the arms or around the groin
• two or more neurofibromas
• a tumour on the optic nerve (an optic glioma), which rarely causes symptoms or affects sight 
• two or more tiny brown spots in the coloured part of the eye (Lisch nodules)
• bone defects, such as bowing of the legs below the knee
• a family history of NF1

It is usually easy to diagnose NF1 in adults, but it can take several years for all the symptoms to develop in children. As a result, it's not always possible to make a firm diagnosis before a child is five years old.

Further testing

Further tests may be recommended to assess whether your child has developed additional symptoms or secondary conditions that are known to be associated with NF1. Some of these tests are described below:

• X-rays can check for any problems with the normal development of the bones.
• MRI scans can produce more detailed images of the soft tissue of the body and check for non-cancerous tumours inside the optic nerve, brain and nervous system.
• A simple blood pressure test will often be used to measure your child’s blood pressure.
• A biopsy, where a small tissue sample is removed from the body for further testing, can be used to check for cancerous cells.
• An electroencephalogram (EEG), which measures electrical activity in the brain, can be used if your child has had seizures (fits).

Genetic testing

If there is uncertainty about the diagnosis, your child can be tested to see whether they have the NF1 mutated gene. This involves extracting DNA from a sample of their blood and analysing it to check whether they have inherited the faulty gene.

However, the test is not always completely reliable. Around 5% of children who test negative for the mutated gene still develop NF1.

Genetic counselling

Couples with a family history of NF1 who are thinking of having a baby can be referred to a genetics specialist for advice.

A genetic counsellor can help couples work through the decision-making process and explain possible alternatives, such as adoption or artificial insemination (where sperm taken from the man is inserted directly into his partner’s womb).

However, NF1 is unpredictable. How mild or severe a parent's symptoms are will not determine how the child will be affected or what complications they may have.

Counselling

Counselling is guided discussion with an independent trained person, to help you find your own answers to a problem or issue.

Genetic

Genetic is a term that refers to genes – the characteristics inherited from a family member.