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Disease Profile

Legius syndrome

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.


US Estimated

Europe Estimated

Age of onset






Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.

Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

Neurofibromatosis type 1 like syndrome


Congenital and Genetic Diseases; Skin Diseases


The following summary is from Orphanet, a European reference portal for information on rare diseases and orphan drugs.

Orpha Number: 137605

Legius syndrome, also known as NF1-like syndrome, is a rare, genetic skin pigmentation disorder characterized by multiple café-au-lait macules with or without axillary or inguinal freckling.

The prevalence of Legius syndrome is not known. Fewer than 200 cases have been reported to date. Prevalence may be higher than expected due to misdiagnosis of cases as neurofibromatosis type 1 (NF1, see this term). The incidence of NF1 is reported to be 1/3000, and about 2% of patients fulfilling diagnostic criteria for NF1 are found to have the genetic mutation underlying Legius syndrome (SPRED1).

Clinical description
The clinical presentation of Legius syndrome is very similar to that of NF1. Patients typically present with multiple café-au-lait spots sometimes associated with intertriginous freckling, but lack Lisch nodules, optic pathway gliomas, bone abnormalities, neurofibromas or other tumor manifestations. The number of café-au-lait macules tends to increase with age during childhood. Other less common manifestations include short stature, macrocephaly, Noonan-like facies, pectus excavatum/carinatum, lipomas, hypopigmented macules, vascular lesions, learning disabilities, attention deficit/hyperactivity disorder (ADHD), and developmental delay.

Legius syndrome is caused by heterozygous inactivating mutations in the SPRED1 gene (15q14), involved in regulation of the RAS-MAPK signal transduction pathway. Nearly 100 different mutations in this gene have been identified. The proportion of cases related to de novo mutations is not yet known. No genotypephenotype correlations have been found.

Diagnostic methods
About 50% of patients with Legius syndrome fulfill the diagnostic criteria for NF1, but they have a far milder phenotype compared to NF1 patients. Diagnosis based solely on the presence of clinical features is difficult, given the overlap with other disorders characterized by multiple café-au-lait spots. The presence of characteristic clinical signs in parents of affected individuals is supportive of diagnosis. However, molecular genetic testing is required to confirm the diagnosis and testing is available on a clinical basis.

Differential diagnosis
Legius syndrome is differentiated from NF1 by the absence of the non-pigmentary clinical manifestations seen in this disorder (i.e. Lisch nodules, neurofibromas, optic glioma, bone abnormalities). Correct diagnosis is essential because of the differences in prognosis and long-term monitoring between Legius syndrome and NF1. Other disorders to consider include Noonan syndrome, Noonan syndrome with lentigines (LEOPARD syndrome), and McCune-Albright syndrome (see these terms).

Antenatal diagnosis
Prenatal diagnosis is possible and requires prior identification of the disease-causing mutation in the family.

Genetic counseling
Legius syndrome follows an autosomal dominant pattern of inheritance. Genetic counseling should be provided to affected families.

Management and treatment
Drug therapy should be considered for the behavioral manifestations of the disorder (ADHD). Physical, speech, and occupational therapy is recommended for those with developmental delay and educational support for those with learning difficulties.

Given the current knowledge of disease manifestations and complications, the prognosis for patients with Legius syndrome is considered to be very good.

Visit the Orphanet disease page for more resources.


This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
5%-29% of people have these symptoms
Abnormal sternum morphology
Abnormality of the sternum
Sternal anomalies

[ more ]

Percent of people who have these symptoms is not available through HPO
Attention deficit hyperactivity disorder
Attention deficit
Attention deficit disorder
Attention deficit-hyperactivity disorder
Attention deficits
Childhood attention deficit/hyperactivity disorder

[ more ]

Autosomal dominant inheritance
Axillary freckling
Cafe-au-lait spot
Downslanted palpebral fissures
Downward slanting of the opening between the eyelids
Eye folds
Prominent eye folds

[ more ]

Generalized hypotonia
Decreased muscle tone
Low muscle tone

[ more ]

High palate
Elevated palate
Increased palatal height

[ more ]

High, narrow palate
Narrow, high-arched roof of mouth
Narrow, highly arched roof of mouth

[ more ]

Wide-set eyes
Widely spaced eyes

[ more ]

Low posterior hairline
Low hairline at back of neck
Low-set, posteriorly rotated ears
Increased size of skull
Large head
Large head circumference

[ more ]

Little lower jaw
Small jaw
Small lower jaw

[ more ]

Multiple lipomas
Multiple fatty lumps
Drooping upper eyelid
Short neck
Decreased length of neck
Specific learning disability
Triangular face
Face with broad temples and narrow chin
Triangular facial shape

[ more ]



Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.

Testing Resources

  • The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.


    Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

    Organizations Supporting this Disease

      Learn more

      These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

      Where to Start

        In-Depth Information

        • GeneReviews provides current, expert-authored, peer-reviewed, full-text articles describing the application of genetic testing to the diagnosis, management, and genetic counseling of patients with specific inherited conditions.
        • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
        • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
        • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
        • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
        • PubMed is a searchable database of medical literature and lists journal articles that discuss Legius syndrome. Click on the link to view a sample search on this topic.