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Neurofibromatosis

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Neurofibromatosis
Classifications and external resources
ICD-10 Q85.0 (M9540/0)
ICD-9 237.7

Neurofibromatosis is an autosomal dominant genetic disorder. It encompasses a set of distinct genetic disorders that cause tumors to grow along types of nerves and, in addition, can affect the development of non-nervous tissues such as bones and skin. The tumors can grow anywhere on or in the body.

Contents

[edit] History

Joseph Merrick, the Elephant Man, was once considered to have been afflicted with either elephantiasis or neurofibromatosis type I. However, it is now generally believed that Merrick suffered from the very rare Proteus syndrome or perhaps a combination of the two conditions.

[edit] Types

Apart from the common form, there are two rarer forms and several even rarer forms:

  • Schwannomatosis is a rare form that is clinically and genetically distinct from types I and II. Multiple Schwannomas (rather than Neurofibromas) occur, and about one-third of patients have these tumors in only one part of the body. Incidence is 1:40,000. The vestibular nerve is spared. Pain is the primary symptom, although numbness, tingling and weakness can also occur. Schwannomas are always benign.

[edit] Symptoms

Neurofibromatosis type 1 - mutation of neurofibromin chromosome 17q11.2

Image:Neurofibromatosis plexiform neurofriboma 3.jpg

Neurofibromatosis type 2 - mutation of merlin chromosome 22q12

Schwannomatosis - gene involved has yet to be identified

  1. Multiple Schwannomas occur.
  2. The Schwannomas develop on cranial, spinal and peripheral nerves.
  3. Chronic pain, and sometimes numbness, tingling and weakness.
  4. About 1/3 of patients have segmental Schwannomatosis, which means that the Schwannomas are limited to a single part of the body, such as an arm, a leg or the spine.
  5. Unlike the other forums of NF, the Schwannomas do not develop on vestibular nerves, and as a result, no loss of hearing is associated with Schwannomatosis.
  6. Patients with Schwannomatosis do not have learning disabilities related to the disease.

[edit] Genetics and Hereditability

Image:Autosomal Dominant Pedigree Chart.svg

Neurofibromatosis type 1 is due to mutation on chromosome 17q11.2 , the gene product being Neurofibromin ( a GTPase activating enzyme).<ref>Fauci,et al Harrison's Principle of Internal Medicine 16th Ed. p 2453 </ref>

Neurofibromatosis type 2 is due to mutation on chromosome 22q , the gene product is Merlin, a cytoskeletal protein.

Both NF1 and NF2 are autosomal dominant disorders, meaning that only one copy of the mutated gene need be inherited to pass the disorder. A child of a parent with NF1 or NF2 and an unaffected parent will have a 50% chance of inheriting the disorder.

Complicating the question of heritability is the distiction between genotype and phenotype, that is, between the genetics and the actual manifestation of the disorder. In the case of NF1, no clear links between genotype and phenotype have been found, and the severity and specific nature of the symptoms may vary widely among family members with the disorder (Korf and Rubenstein 2005). In the case of NF2, however, manifestations are similar among family members; a strong genotype-phenotype correlation is believed to exist (ibid).

Both NF1 and NF2 can also appear spontaneously through random mutation, with no family history. These spontaneous or sporadic cases account for about one half of neurofibromatosis cases (ibid).

[edit] Family

Neurofibromatosis is considered a member of the neurocutaneous syndromes (phakomatoses). In addition to the types of neurofibromatosis, the phakomatoses also include tuberous sclerosis, Sturge-Weber syndrome and von Hippel-Lindau disease. This grouping is an artifact of an earlier time in medicine, before the distinct genetic basis of each of these diseases was understood.

[edit] Neurofibromatosis in Pop Culture

In the television series Dallas, the inherited neurofibromatosis of the Barnes family is a driving plot device, though the portrayal of the condition does leave something to be desired in terms of scientific fact.

[edit] External links

[edit] Notes

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[edit] References

Korf, Bruce E. and Allan E. Rubenstein. 2005. Neurofibromatosis: A Handbook for Patients, Families, and Health Care Professionals. [1]de:Neurofibromatose es:Neurofibromatosis fr:Neurofibromatose nl:Neurofibromatose ja:神経線維腫症 no:Nevrofibromatose

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