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Neurofibromatosis
 

Neurofibromatosis is an autosomal dominant genetic disorder.

Types

There are two major forms and one newly discovered form:

  • 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. The vestibular nerve is spared. Pain is the primary symptom, although numbness, tingling and weakness can also occur.

  • Six other, extremely rare, forms are also recognized:

Symptoms

Neurofibromatosis type 1 - mutation on chromosome 17

Neurofibromatosis type 2 - mutation on chromosome 22

Genetics and Hereditability

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

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).

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

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.

External links

Notes

References

Korf, Bruce E. and Allan E. Rubenstein. 2005. Neurofibromatosis: A Handbook for Patients, Families, and Health Care Professionals. Congenital_genetic_disorders | Genetic disorders | Dermatology | Neurology

Neurofibromatose | Neurofibromatosis | Neurofibromatose | 神経線維腫症 | Neurofibromatose | Nevrofibromatose

 

This article is licensed under the GNU Free Documentation License. It uses material from the "Neurofibromatosis".

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