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What is Legius Syndrome?

Legius Syndrome is named after the Belgian doctor Professor Eric Legius who first identified it as a distinct condition. It is also called SPRED1 and has been known as “NF1-like syndrome” because of the similarities the conditions share, and the location of the genetic “spelling mistake” that gives rise to this condition.

Legius Syndrome has some similarities with Neurofibromatosis Type 1 but as molecular genetic testing has developed, it became apparent that this is a separate and different condition.
NF1 is located on chromosome 17. Legius Syndrome is located on chromosome 15.

Legius Syndrome is a dominant condition which means there is a 50% chance of an affected parent passing it on to each of their children.

What is Legius Syndrome?

Legius Syndrome is a condition that is characterised by changes in skin pigmentation (colouring). Almost everyone with Legius Syndrome has multiple cafe au lait patches on their skin. These patches look the same as the ones you would see on someone who has NF1.

People with Legius Syndrome also have freckling in the armpit and groins. They also tend to have a larger than average head and mild learning difficulties. These characteristics are also seen in NF1.

The main difference between Legius and NF1 is that patients do not develop neurofibromas. Nor do they have any of the health complications that are linked to NF1.

How can the doctor tell if I have NF1 or Legius Syndrome?

If a patient is referred to the regional genetics service because they have cafe au lait patches and freckling, NF1 will be the most likely explanation. If the doctor thinks there is some doubt about the diagnosis and the situation needs clarifying, a genetic test can be undertaken.

About 95% of children who have more than 6 cafe au lait patches will go on to develop NF1.

Most individuals who are diagnosed with Legius Syndrome will have a parent who has the same condition.

It is important to be clear whether a person has NF1 or Legius syndrome to ensure the correct diagnosis has been made in the first place, so the family has accurate information.
Legius Syndrome is managed in a different way to NF1. Children with Legius Syndrome do not need the same health checks throughout childhood as a child with NF1 because they do not share the risk of NF1-related health complications. However, a developmental assessment should be undertaken to ensure appropriate resources are in place to support the child if necessary.

Legius Syndrome is regarded as a comparatively mild condition that does not bring the same burden of health care as NF1.