ConditionSkin, hair & nails
Legius Syndrome
Legius syndrome is a rare, usually mild genetic condition caused by changes in the SPRED1 gene. It causes multiple cafe-au-lait spots (flat, light-brown patches) and freckling in the armpits or groin, and sometimes a large head, learning or attention difficulties. It closely resembles neurofibromatosis type 1 (NF1) in childhood, but people with Legius syndrome do not develop neurofibromas, optic gliomas or other NF1 tumors. Genetic testing tells the two apart, which spares families unnecessary tumor screening.
Also called: NF1-like syndrome, SPRED1-related disorder, neurofibromatosis type 1-like syndrome
At a glance
- What it is
- An inherited condition from a SPRED1 gene change, causing pigment changes similar to NF1.
- Main signs
- Six or more cafe-au-lait spots, freckling in skin folds, sometimes a large head, learning or attention problems.
- What it lacks
- Neurofibromas, Lisch nodules, optic pathway gliomas and the bone changes of NF1.
- Inheritance
- Autosomal dominant. Each child of an affected parent has a 50% chance of inheriting it.
- Management
- Genetic confirmation, developmental and school support. Tumor surveillance is not needed.
When to get help
Book a routine appointment
- A child with six or more cafe-au-lait spots, or freckling in the armpits or groin (genetic evaluation)
- Learning, attention or speech difficulties in a child with Legius syndrome
- Planning a pregnancy when a parent has Legius syndrome
- A new lump under the skin, vision change or bone problem in a child with suspected Legius syndrome (to recheck for NF1)
Usually safe to manage at home
- One or two cafe-au-lait spots in an otherwise healthy child, which are common and usually need no tests
What Legius syndrome is
Legius syndrome was described in 2007. The SPRED1 gene makes a protein that dampens the RAS-MAPK pathway, a signaling system that controls cell growth. A change in SPRED1 leaves this pathway slightly overactive. The same pathway is affected in NF1 and Noonan syndrome, which is why these conditions overlap. Disorders of this pathway are called RASopathies.
It is estimated to be much rarer than NF1. A meaningful minority of children who have multiple cafe-au-lait spots but no other NF1 signs and no NF1 gene change turn out to have Legius syndrome.
Signs and symptoms
- cafe-au-lait macules: flat, smooth-edged, light-brown spots, usually six or more, appearing in infancy or early childhood. See cafe-au-lait macules
- freckling in skin folds: armpits and groin
- macrocephaly: a larger-than-average head
- learning disabilities, attention problems or ADHD, and mild developmental delays in some children
- Noonan-like facial features occasionally
- lipomas (soft fatty lumps) in some adults
What does not occur
People with Legius syndrome do not develop:
- neurofibromas (benign nerve sheath tumors on or under the skin)
- plexiform neurofibromas
- optic pathway gliomas
- Lisch nodules in the eye
- characteristic bone abnormalities of NF1
Legius syndrome vs NF1
| Legius syndrome | Neurofibromatosis type 1 | |
|---|---|---|
| Gene | SPRED1 | NF1 |
| Cafe-au-lait spots and freckling | Yes | Yes |
| Neurofibromas | No | Yes, increasing with age |
| Optic glioma | No | Yes, in about 15% of children |
| Lisch nodules | No | Yes, most adults |
| Bone problems | No | Possible (scoliosis, tibial bowing) |
| Cancer risk | Not clearly increased | Increased risk of certain tumors |
| Surveillance needed | Development and learning | Yearly eye exams, skin, blood pressure, spine and more |
In young children, the two can look identical, because NF1 tumors appear later. That is why genetic testing is important.
Diagnosis
- Clinical examination: counting and measuring cafe-au-lait spots, checking for freckling, neurofibromas and other features, and an eye exam.
- Genetic testing: a multigene panel including NF1 and SPRED1. Finding a SPRED1 change confirms Legius syndrome. Revised 2021 international criteria require genetic confirmation to diagnose Legius syndrome.
- Family assessment: examining parents for cafe-au-lait spots, since many inherit the condition from a mildly affected parent.
Management
There is no specific treatment, and none is usually needed beyond support:
- developmental and educational assessment, with early intervention, speech therapy or school support as needed
- ADHD evaluation and treatment if attention problems are present
- routine pediatric care, with growth and head size monitoring
- genetic counseling for families
- cosmetic options such as laser treatment for spots, if desired, although results vary
Because Legius syndrome does not cause NF1 tumors, children do not need the intensive tumor surveillance recommended for NF1, such as yearly specialist eye exams for optic gliomas.
Outlook
Legius syndrome is generally mild, and life expectancy is normal. The main challenges are learning and attention difficulties in some children, which respond to support. Adults may notice lipomas. Research continues on whether there are any other long-term health risks.
Frequently asked questions
What is Legius syndrome?
Legius syndrome is a mild genetic condition caused by changes in the SPRED1 gene. It causes multiple cafe-au-lait spots and freckling, sometimes with a large head and learning or attention difficulties, but not the tumors seen in neurofibromatosis type 1.
How is Legius syndrome different from NF1?
Both cause cafe-au-lait spots and freckling. NF1 also causes neurofibromas, optic gliomas, Lisch nodules and bone problems, and needs regular tumor surveillance. Legius syndrome does not cause these and is caused by a different gene, SPRED1 rather than NF1.
Is Legius syndrome inherited?
Yes. It is inherited in an autosomal dominant pattern, so a parent with Legius syndrome has a 50% chance of passing it to each child. Some cases are due to a new gene change in the child. Genetic counseling can explain the risks.
How many cafe-au-lait spots are concerning?
One to three cafe-au-lait spots are common in healthy children. Six or more spots larger than 5 mm before puberty, or larger than 15 mm after puberty, raise the possibility of NF1 or Legius syndrome and warrant evaluation.
Does Legius syndrome cause cancer?
Current evidence does not show a clearly increased cancer risk in Legius syndrome, unlike NF1. People with Legius syndrome do not develop neurofibromas or optic gliomas, so they do not need NF1-style tumor screening.
Sources
This guide was written from current patient and clinical guidance, including:
- GeneReviews (NCBI): Legius syndrome
- MedlinePlus Genetics: Legius syndrome
- Children's Tumor Foundation: Legius syndrome
- American Academy of Pediatrics: Health supervision for children with neurofibromatosis type 1
- Revised diagnostic criteria for NF1 and Legius syndrome (international consensus, Genetics in Medicine 2021)