Academic journal article Bulletin of the World Health Organization

Prevention and Control of Neurofibromatosis: Memorandum from a Joint WHO/NNFF Meeting

Academic journal article Bulletin of the World Health Organization

Prevention and Control of Neurofibromatosis: Memorandum from a Joint WHO/NNFF Meeting

Article excerpt

Introduction

Neurofibromatosis (NF) is a serious, genetically determined neurological disorder, with a prevalence of about 1:4000 births, affecting both sexes and all races and ethnic groups. The term "neurofibromatosis" encompasses at least two distinct disorders which have in common a predisposition to the development of tumours of the nerve sheath. Both forms (known as NF1 and NF2) are genetically transmitted as autosomal dominant traits and are distributed throughout the world with no apparent racial or ethnic predilection. Clinical management of persons with NF is complicated by a wide range of variability of expression, often impeding accurate diagnosis, and making it difficult to predict the clinical course [1-3].

Until the last decade, very little research had been undertaken into the cause of the different forms of NF because the challenge presented by this disorder may have actually hampered such studies. The problems caused by NF can take a patient to any of the major medical specialties and are individually relatively infrequent, so that no one group of health professionals realizes the overall health burden of the disease. Prior to the advent of DNA technology relatively little basic research into NF had been carried out. The recent discovery and isolation of the gene responsible for the NF1 mutation has made it highly appropriate to discuss the applicability, at the practical level, of the new findings that could modify the approaches to diagnosis, treatment and prevention of NF.

Definition, frequency and heterogeneity

The NF1 and NF2 nemenclature for the two major forms was suggested in 1987 by a National Institutes of Health Consensus Development Conference on Neurofibromatosis [4]; their diagnostic criteria are given in Tables 1 and 2. NF1 is more common, affecting approximately 1:4000 individuals worldwide; its characteristics are cafe-au-lait spots, Lisch nodules, and neurofibromas; other manifestations include optic gliomas, skeletal dysplasias, plexiform neurofibromas, learning disabilities, etc. NF2 is far less common, with a frequency of about 1:100 000; it is characterized by the occurrence of bilateral acoustic neuromas, as well as meningiomas, schwannomas, neurofibromas, and bilateral posterior subcapsular cataracts. NF1 is the disorder sometimes referred to as von Recklinghausen or "peripheral" neurofibromatosis. NF2 has been called bilateral acoustic or "central" neurofibromatosis.

Table 1: Diagnostic criteria for NF1
NF1 should be considered if two of the following are present
in an individual, provided no other disease accounts for the
findings:
1. On examination in room light, there are at least 5 cafe-au-lait
   macules (over 5 mm in greatest diameter), if prepubertal;
   or 6 cafe-au-lait macules (over 15 mm in greatest diameter),
   if post-pubertal.
2. Based on the history or on clinical grounds, there are 2 or
   more neurofibromas of any type, or 1 plexiform
   neurofibroma.
3. Multiple freckles in the axillary or inguinal regions.
4. Sphenoid wing dysplasia or congenital bowing or thinning of
   long bone cortex, with or without pseudoarthrosis.
5. Optic nerve glioma.
6. Two or more iris Lisch nodules on slit-lamp examination.
7. A first-degree relative (parent, sibling or offspring) has NF1,
   by the above criteria.
Table 2: Diagnostic criteria for NF2
NF2 should be considered if either of the following is present in
an individual:
1. Evidence, by computer tomography (CT) or magnetic
   resonance imaging (MRI), of bilateral internal auditory canal
   masses, consistent with acoustic neuromas.
2. A first-degree relative has bilateral acoustic
   neurofibromatosis and one of the following:
   -- CT or MRI evidence of a unilateral internal auditory
      canal mass, consistent with acoustic neuroma.
   -- A plexiform neurofibroma or two of the following:
      meningioma, glioma, neurofibroma at any site. … 
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