Neurofibromatosis

Source: Wikipedia, the free encyclopedia.

Neurofibromatosis
neurofibromatosis type 2 (NF2), schwannomatosis[1]
CausesGenetic[1]
Diagnostic methodSymptoms, genetic testing[2]
TreatmentSurgery, radiation therapy[2]
PrognosisNF1: variable, but most of the time normal life expectancy[1]
NF2: shortened life expectancy[1]
Frequency1 in 3,000 people (United States)[1]

Neurofibromatosis (NF) refers to a group of three distinct genetic conditions in which

benign) and often involve the skin or surrounding bone.[1] Although symptoms are often mild, each condition presents differently. Neurofibromatosis type I (NF1) is typically characterized by café au lait spots (light-brown flat patches of skin), neurofibromas (small bumps in or under the skin), scoliosis (side-way curvature of the back), and headaches.[2] Neurofibromatosis type II (NF2), on the other hand, may present with early-onset hearing loss, cataracts, tinnitus, difficulty walking or maintain balance, and muscle atrophy.[2] The third type is called schwannomatosis and often presents in early adulthood with widespread pain, numbness, or tingling due to nerve compression.[3]

The cause is a

biopsy.[5][3] Genetic testing may rarely be done to support the diagnosis.[2]

There is no known prevention or cure.[1][2] Surgery may be done to remove tumors that are causing problems or have become cancerous.[1] Radiation and chemotherapy may also be used if cancer occurs.[1] A cochlear implant or auditory brainstem implant may help some who have hearing loss due to the condition.[1]

In the United States, about 1 in 3,500 people have NF1 and 1 in 25,000 have NF2.[1] Males and females are affected equally often.[2] In NF1, symptoms are often present at birth or develop before 10 years of age.[1] While the condition typically worsens with time, most people with NF1 have a normal life expectancy.[1] In NF2, symptoms may not become apparent until early adulthood.[1] NF2 increases the risk of early death.[1] Descriptions of the condition occur as far back as the 1st century.[6] It was formally described by Friedrich Daniel von Recklinghausen in 1882, after whom it was previously named.[4]

Signs and symptoms

Lisch nodules as seen in NF1
Person with multiple small neurofibromas in the skin and a "café au lait spot" (bottom of photo, to the right of centre). A biopsy has been taken of one of the lesions.

Neurofibromatosis type 1 in early life may cause learning and behavior problems – about 60% of children who have NF1 have mild difficulty in school.[7] Signs the individual might have are as follows:[8][9]

People with neurofibromatosis type 2 can exhibit the same type of skin symptoms as type 1, but not necessarily in every case.[10] Symptoms may include pain due to pressure on nerves, tinnitus, weakness in fingers, numbness, headaches. The symptom most characteristic of NF2 is hearing loss.[11] The hearing loss occurs due to the pressure of tumors on the acoustic nerve. The same pressure can cause headaches, dizziness, and nausea.[10]

The main symptom of schwannomatosis is localized pain. This pain is due to tissues and nerves experiencing more pressure because of nearby tumors.[12]

  • Figure of various morbidities associated with neurofibromatosis type II.[13]
    Figure of various morbidities associated with neurofibromatosis type II.[13]

Cause

Diagram of autosomal dominant inheritance pattern

The three types of neurofibromatosis are caused by different mutations on chromosomes. NF1 is caused by a mutation on the NF1 gene on the arm of chromosome 17.[4] NF2 is caused by a mutation on the NF2 tumor suppressor gene on chromosome 22.[4] Schwannomatosis is caused by various mutations on chromosome 22.[4]

Neurofibromatosis is an

autosomal dominant disorder, which means only one copy of the affected gene is needed for the disorder to develop.[4] If one parent has neurofibromatosis, his or her children have a 50% chance of developing the condition as well. The severity of the parent's condition does not affect the child; the affected child may have mild NF1 even though it was inherited from a parent with a severe form of the disorder.[14]
The types of neurofibromatosis are:

  • Neurofibromatosis type I, in which the nerve tissue grows tumors (neurofibromas) that may be benign, but may cause serious damage by compressing nerves and other tissues.[15]
  • Neurofibromatosis type II, in which bilateral acoustic neuromas (tumors of the vestibulocochlear nerve or cranial nerve 8 (CN VIII) also known as schwannoma) develop, often leading to hearing loss.[16]
  • Schwannomatosis, in which painful schwannomas develop on spinal and peripheral nerves.[17]

Pathophysiology

The pathophysiology is varied, and each NF type has a different one:

  • Neurofibromatosis type I is the most common of the three types and is caused by genetic changes in the NF1 gene located on chromosome 17 (17q11.2). This gene encodes a cytoplasmic protein known the neurofibromin, which functions as a
    tumor suppressor and therefore serves as a signal regulator of cell proliferation and differentiation.[18][19] A dysfunction or lack of neurofibromin can affect regulation, and cause uncontrolled cell proliferation, leading to the tumors (neurofibromas) that characterize NF1. The neurofibromas caused by NF consist of Schwann cells, fibroblasts, perineuronal cells, mast cells and axons embedded in an extracellular matrix.[20][21] Another function of neurofibromin is to bind to microtubules that play a role in the release of adenylyl cyclase and its activity.[20] Adenylyl cyclase plays an essential role in cognition.[20] Neurofibromin's role in the activity of adenylyl cyclase explains why patients with NF experience cognitive impairment.[20]
  • Neurofibromatosis type II is caused by a mutation on chromosome 22 (22q12).[22] The mutation falls on the NF2 tumor suppressor gene.[22] The gene normally encodes a cytoplasmic protein known as merlin. The normal function of merlin is to regulate the activity of multiple growth factors, the mutated copy of the gene leads to merlin's loss of function.[22] The loss of function leads to increased activity of growth factors normally regulated by merlin, leading to the formation of the tumors associated with NF2.[22]
  • Schwannomatosis is caused by a mutation on the SMARCB1 gene.[12] This gene is located near the NF2 tumor suppressor gene leading to the thought that schwannomatosis and NF2 were the same condition. The two conditions show different mutations on two different genes. The normal function of the SMARCB1 gene is to encode a protein called SMARCB1 that is part of a larger protein complex whose function is not completely understood.[12] The complex including SMARCB1 plays a role in tumor suppression.[12] The mutation of the SMARCB1 gene causes a loss of function in the complex leading to the formation of tumors indicative of schwannomatosis.[12]

Diagnosis

The neurofibromatoses are considered as

neurocutaneous syndromes (phakomatoses).[23]
The diagnosis of neurofibromatosis is done via the following means:[24]

Differential diagnosis

Conditions similar to NF include:

Treatment

Surgical removal of tumors is an option; however, the risks involved should be assessed first.[28] With regard to OPG (optic pathway gliomas), the preferred treatment is chemotherapy. However, radiotherapy is not recommended in children who present with this disorder.[29] It is recommended that children diagnosed with NF1 at an early age have an examination each year, which allows any potential growths or changes related to the disorder to be monitored.[30]

Prognosis

In most cases, symptoms of NF1 are mild, and individuals live normal and productive lives. In some cases, however, NF1 can be severely debilitating and may cause cosmetic and

brain stem, can be life-threatening. Most individuals with schwannomatosis have significant pain. In some extreme cases, the pain will be severe and disabling.[9]

Epidemiology

In the United States, about 1 in 3,500 people have NF1, 1 in 25,000 have NF2, and 1 in 40,000 have schwannomatosis.[1] Males and females are affected equally often in all three conditions.[2] In NF1, symptoms are often present at birth or develop before 10 years of age.[1] While the condition typically worsens with time, most people with NF1 have a normal life expectancy.[1] In NF2, symptoms may not become apparent until early adulthood.[1] NF2 increases the risk of early death.[1] Schwannomatosis symptoms develop in early childhood and can worsen with time. Typically life expectancy is unaffected in those with schwannomatosis.[3]

History

Descriptions of what is believed to be the condition go as far back as the 1st century.[6] The conditions were formally described by Friedrich Daniel von Recklinghausen in 1882, after whom it was previously named.[4]

References

  1. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab "Neurofibromatosis Fact Sheet". NINDS. 3 February 2016. Archived from the original on 23 January 2018. Retrieved 16 April 2018. Public Domain This article incorporates text from this source, which is in the public domain.
  2. ^ a b c d e f g h "Learning about Neurofibromatosis". National Human Genome Research Institute (NHGRI). 16 August 2016. Archived from the original on 10 October 2016. Retrieved 7 November 2016.Public Domain This article incorporates text from this source, which is in the public domain.
  3. ^
    PMID 29517885. Retrieved 21 November 2019. {{cite book}}: |website= ignored (help
    )
  4. ^
    S2CID 239484110
    . Retrieved 22 November 2019.
  5. PMID 29083784
    .
  6. ^
    ISBN 978-0-85729-628-3. Archived
    from the original on 10 September 2017. Retrieved 9 October 2015.
  7. ^ "Neurofibromatosis". NHS Choices. NHS. Archived from the original on 25 September 2015. Retrieved 9 October 2015.
  8. ^ "Neurofibromatosis". NINDS. NIH. Archived from the original on 4 October 2015. Retrieved 9 October 2015.
  9. ^ a b "NINDS Neurofibromatosis Information Page". 23 February 2015. Archived from the original on 4 April 2015. Retrieved 21 April 2015.
  10. ^
    ISBN 978-1-4144-7602-5
    .
  11. S2CID 11130733
    .
  12. ^
    PMID 23401320
    .
  13. PMID 33445724
    .
  14. ^ "Neurofibromatosis type 1 - Causes". NHS Choices. Archived from the original on 24 September 2015. Retrieved 9 October 2015.
  15. ^ "Neurofibromatosis type 1". Genetics Home Reference. 5 October 2015. Archived from the original on 10 September 2015. Retrieved 9 October 2015.
  16. ^ "Neurofibromatosis type 2". Genetics Home Reference. 5 October 2015. Archived from the original on 10 September 2015. Retrieved 9 October 2015.
  17. ISBN 978-0-443-06982-6. Archived
    from the original on 2 May 2016.
  18. PMID 2134734
    .
  19. ^ "Orphanet: Neurofibromatosis type 1". www.orpha.net. Archived from the original on 6 October 2015. Retrieved 13 October 2015.
  20. ^
    PMID 16957683
    .
  21. PMID 19539839
    .
  22. ^
    S2CID 21986493
    .
  23. ISBN 978-1-60714-653-7
    .
  24. ^ "Neurofibromatosis. What is neurofibromatosis? Type 1 (NF1) | Patient". Patient. Archived from the original on 4 October 2015. Retrieved 9 October 2015.
  25. PMID 20301288. Archived
    from the original on 18 January 2017.
  26. PMID 20945555. Archived
    from the original on 10 September 2017.
  27. PMID 28377973
    .
  28. ^ "Neurofibromatosis type 2 - Treatment". NHS Choices. Archived from the original on 22 December 2015. Retrieved 11 October 2015.
  29. ^ "Complex Neufibrmatosis type 1" (PDF). NHS.uk. NHS. Archived (PDF) from the original on 23 December 2015. Retrieved 13 October 2015.
  30. ^ "Neurofibromatosis type 1 - Treatment". NHS Choices. Archived from the original on 26 September 2015. Retrieved 11 October 2015.

Further reading

External links

Scholia has a topic profile for Neurofibromatosis.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Neurofibromatosis&oldid=1219698054"