Rare Pediatrics News

Disease Profile

Linear nevus sebaceous syndrome

Prevalence
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.

Unknown

Age of onset

Neonatal

ICD-10

Q85.8

Inheritance

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

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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

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X-linked
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.

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

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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.

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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.

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Not applicable

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Other names (AKA)

Schimmelpenning Feuerstein Mims syndrome; Sebaceous nevus syndrome linear; SFM syndrome;

Categories

Congenital and Genetic Diseases; Eye diseases; Rare Cancers;

Summary

Linear nevus sebaceous syndrome (LNSS) is a condition characterized by the association of a large, linear sebaceous nevus (type of birthmark) with a broad range of abnormalities that may affect every organ system, including the central nervous system (CNS).[1] The nevus usually is located on the face, scalp, or neck.[1][2] The most common CNS abnormalities are intellectual disability, seizures, and hemimegalencephaly (abnormal enlargement of one side of the brain).[1][2] Various other CNS abnormalities have been reported.[2] Other signs and symptoms may include various eye abnormalities; skeletal (bone) deformities; heart defects; urogenital abnormalities; and an increased risk of cancer with age.[1][3][4] LNSS is not inherited (it is sporadic). It can be caused by a somatic mutation in any of several genes. Mutations that cause LNSS occur after fertilization and are only present in some body cells (mosaicism).[5] Treatment is directed towards the specific symptoms in each person.[6]

Symptoms

Linear nevus sebaceous syndrome (LNSS) is characterized by the presence of a large, linear sebaceous nevus (type of birthmark usually present from birth) with a broad range of abnormalities that may affect every organ system, including the central nervous system (CNS).[1] The specific symptoms and severity can vary greatly from one person to another.[6]

The sebaceous nevus usually is located on the face, scalp, or neck.[1][2] It can also be located on the arms, legs or trunk. While the nevus may be barely noticeable at birth, it typically becomes more pronounced with age (usually around puberty) and may appear scaly, warty or thickened. It typically does not cause any symptoms.[6]

A variety of CNS abnormalities have been reported in people with LNSS. The most common are intellectual disability, seizures, and hemimegalencephaly (abnormal enlargement of one side of the brain).[1][2] Other reported CNS abnormalities include:[6]

  • Dandy-Walker malformation
  •  abnormal formation of certain brain vessels
  •  agenesis of the corpus callosum (absence of nerve tissue that connects the two sides of the brain)
  • defects of the folds of the brain, such as a lack of folds (agyria), small folds (microgyria) or thickened folds (pachygyria).

Other signs and symptoms of LNSS may include:[1][6][2]

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:
HPO ID
80%-99% of people have these symptoms
Adenoma sebaceum
0009720
Alopecia
Hair loss
0001596
Aplasia/Hypoplasia of the cerebellum
Absent/small cerebellum
Absent/underdeveloped cerebellum

[ more ]

0007360
Asymmetric growth
Uneven or disproportionate growth of one body part compared to another
0100555
Biparietal narrowing
0004422
Cavernous hemangioma
Collection of dilated blood vessels that forms mass
0001048
EEG abnormality
0002353
Frontal bossing
0002007
Genu recurvatum
Back knee
Knee hyperextension

[ more ]

0002816
Hyperreflexia
Increased reflexes
0001347
Intellectual disability
Mental deficiency
Mental retardation
Mental retardation, nonspecific
Mental-retardation

[ more ]

0001249
Iris coloboma
Cat eye
0000612
Melanocytic nevus
Beauty mark
0000995
Microphthalmia
Abnormally small eyeball
0000568
Muscular hypotonia
Low or weak muscle tone
0001252
Prominent occiput
Prominent back of the skull
Prominent posterior skull

[ more ]

0000269
Reduced tendon reflexes
0001315
Seizure
0001250
Telecanthus
Corners of eye widely separated
0000506
Vertebral segmentation defect
0003422
30%-79% of people have these symptoms
Abnormality of vision
Abnormality of sight
Vision issue

[ more ]

0000504
Facial asymmetry
Asymmetry of face
Crooked face
Unsymmetrical face

[ more ]

0000324
Irregular hyperpigmentation
0007400
Plagiocephaly
Flat head syndrome
Flattening of skull
Rhomboid shaped skull

[ more ]

0001357
Porencephalic cyst
Cavity within brain
0002132
5%-29% of people have these symptoms
Aplasia/Hypoplasia of the corpus callosum
0007370
Cerebral calcification
Abnormal deposits of calcium in the brain
0002514
Corneal opacity
0007957
Dandy-Walker malformation
0001305
Growth delay
Delayed growth
Growth deficiency
Growth failure
Growth retardation
Poor growth
Retarded growth

[ more ]

0001510
Hyperphosphaturia
High urine phosphate levels
0003109
Ophthalmoplegia
Eye muscle paralysis
0000602
Precocious puberty
Early onset of puberty
Early puberty

[ more ]

0000826
Percent of people who have these symptoms is not available through HPO
Abnormality of dental color
Abnormality of tooth color
Abnormality of tooth shade

[ more ]

0011073
Abnormality of dental morphology
Abnormality of dental shape
Abnormally shaped teeth
Deformity of teeth
Dental deformity
Dental malformations
Malformed teeth
Misshapen teeth
Misshapened teeth

[ more ]

0006482
Abnormality of finger
Abnormalities of the fingers
0001167
Abnormality of toe
Abnormalities of the toes
0001780
Basal cell carcinoma
0002671
Coarctation of aorta
Narrowing of aorta
Narrowing of the aorta

[ more ]

0001680
Coloboma
Notched pupil
0000589
Cranial asymmetry
0000267
Hemangioma
Strawberry mark
0001028
Hemihypertrophy
Asymmetric overgrowth
0001528
Hemimegalencephaly
0007206
Horseshoe kidney
Horseshoe kidneys
0000085
Hypophosphatemic rickets
0004912
Hypopigmentation of the skin
Patchy lightened skin
0001010
Ichthyosis
0008064
Kyphoscoliosis
0002751
Linear nevus sebaceous
0010817
Nevus sebaceous
0010815

Cause

Linear nevus sebaceous syndrome (LNSS) can be caused by a somatic mutation in any of several genes, including the HRAS, KRAS and NRAS genes.[5] Mutations that cause LNSS occur after fertilization (they are not inherited) and are only present in some body cells (mosaicism).[5] These three genes belong to a class of genes called oncogenes, which when mutated, have the potential to cause normal cells to become cancerous. They play important roles in cell division, cell differentiation (the process by which cells learn to do specific "jobs") and the self-destruction of cells (apoptosis).[7]

Somatic mutations in several genes, including HRAS and KRAS, are responsible for causing isolated nevus sebaceous.[5] It is thought that the additional signs and symptoms in people with LNSS occur because the somatic mutation affects other tissues in addition to the skin.[7] While it is unclear exactly how mutations cause the additional symptoms of LNSS, it may relate to disrupted regulation of cell growth and division.

Diagnosis

A diagnosis of linear nevus sebaceous syndrome (LNSS) is made by identifying the characteristic symptoms, which include a sebaceous nevus along with abnormalities affecting other organ systems.[6]

Because of the potential for multi-system involvement, anyone suspected of having LNSS should have a number of evaluations to determine the presence and extent of associated symptoms. These may include:[1][6]

  • imaging studies such as CT scan or MRI of the brain (some researchers think these should be avoided unless there are signs of central nervous system involvement)
  • an electroencephalogram if epilepsy is present
  • analysis of skin biopsies
  • a complete ophthalmic (eye) exam
  • a skeletal survey
  • chests x-rays

Treatment

Treatment for linear nevus sebaceous syndrome (LNSS) is directed towards the specific symptoms and severity in each affected person. Management may require coordinated efforts of a team of specialists that may consist of pediatricians, pediatric neurologists, dermatologists, orthopedists, ophthalmologists, and other healthcare professionals.

Those who are concerned about cosmetic appearance regarding the nevus might consider surgery to remove the nevus. Surgery used to be recommended due to the risk of becoming cancerous (malignant); however, the risk of malignancy is now much less than previously believed. Surgical removal of the nevus may not always be possible due to its specific location.

Additional treatments depend on the specific abnormalities present and usually follow standard guidelines in the general population for these abnormalities. For example, epilepsy may be treated with antiseizure medications.[6]

Organizations

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

    • The New Zealand Dermatolgical Society's Web site has information on nevus sebaceous, including information on linear nevus sebaceous syndrome. Click on the link above to view this information page. 
    • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

      In-Depth Information

      • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
      • MeSH® (Medical Subject Headings) is a terminology tool used by the National Library of Medicine. Click on the link to view information on this topic.
      • 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 Linear nevus sebaceous syndrome. Click on the link to view a sample search on this topic.

        References

        1. Shay Menascu. Linear nevus sebaceus syndrome. Orphanet. June, 2008; https://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=en&Expert=2612.
        2. Pauline L, Kannan B, Saravannan V, Eswaradass VP. Linear nevus sebaceous syndrome. Ann Indian Acad Neurol. October, 2014; 17(4):468-469.
        3. Terenzi V, Indrizzi E, Buonaccorsi S, Leonardi A, Pellacchia V, Fini G.. Nevus sebaceus of Jadassohn. J Craniofac Surg. 2006; https://www.ncbi.nlm.nih.gov/pubmed/17119437.
        4. Santibanez-Gallerani A, Marshall D, Duarte AM, Melnick SJ, Thaller S.. Should nevus sebaceus of Jadassohn in children be excised? A study of 757 cases, and literature review. J Craniofac Surg. 2003; https://www.ncbi.nlm.nih.gov/pubmed/14501324.
        5. Ada Hamosh. SCHIMMELPENNING-FEUERSTEIN-MIMS SYNDROME; SFM. OMIM. November 24, 2014; https://www.omim.org/entry/163200.
        6. Schimmelpenning Syndrome. NORD. 2015; https://rarediseases.org/rare-diseases/schimmelpenning-syndrome/.
        7. HRAS gene. Genetics Home Reference. August, 2016; https://ghr.nlm.nih.gov/gene/HRAS.

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