Neurofibromatosis Flashcards
def
an autosomal dominant genetic disorder affecting cells of the neural crest, resulting in the development of multiple neurocutaneous tumours
what are the two types of neurofibromatosis
1 Type 1 NF (von Recklinghausens disease)
2. Type 2 NF
what is Type 1 NF (von Recklinghausens disease)
characterised by: 1 many cafe-au-lait spots 2 freckling (axillary/inguinal) 3 neurofibromas 4 lisch nodules
what is Type 2 NF
characterised by:
1 few cafe-au-lait spots
2 bilateral vestibular schwannomas
3 juvenile posterior subcapsular lenticular opacity (cataract)
aetiology of Type 1 NF (von Recklinghausens disease)
mutation in NF1 gene which encodes neurofibromin (GTPase activating protein)
this results in excess activity of proto-oncogene p21-ras
which chromosome is NF1 gene found on
17
aetiology of Type 2 NF
mutations in NF2 gene which encords merlin (or schwannomin)
which chromosome is NF2 gene found on1
22
epi
NF1>NF2
no gender or racial predilection
risk factors for NF
parent with NF
history of Type 1 NF (von Recklinghausens disease)
1 skin lesions
2 learning difficulties (common)
3 visual disturbances (optic gliomas)
4 precocious puberty
why might precocious puberty occur in Type 1 NF (von Recklinghausens disease)
lesions in the pituitary may occur due to optic glioma involving the chiasm
history of Type 2 NF
1 hearing loss or tinnitus (ringing in ears)
2 balance problems
3 facial pain/numbness
examination of Type 1 NF (von Recklinghausens disease)
1 cafe-au-lait spots
2 freckling (armpit/groin)
3 neurofibromas
4 lisch nodules
what are cafe-au-lait spots
flat coffee coloured patches of skin seen in 1st year of life
when does freckling in Type 1 NF usually present
by 10yrs
what are neurofibromas
a tumour formed on a nerve cell sheath
dermal neurofibromas:
they are small violet coloured nodules with a jelly like consistency
nodular neurofibromas:
firm and clearly demarcated
give rise to paraesthesiae (pins + needles) if pressed
what are lisch nodules
small regular brown or translucent mounds (hamartomas) on the iris
aggregation of dendritic melanocytes
examination of Type 2 NF
1 absent/few skin lesions
2 bilateral vestibular schwannomas AKA acoustic neuromas
-are characteristic
-sensorineural hearing loss
3 juvenile posterior subcapsular lenticular opacity (cataracts)
-presents before other manifestations
-screening tool
investigations
1 opthalmological assessment
2 audiometry
3 MRI brain + spinal cord
-for vestibular schwannomas, meningiomas, nerve root neurofibromas
what are the diagnostic criteria for NF 1 (von Recklinghausens disease)
diagnosis if 2 of the following are found:
1 6 or more cafe-au-lait spots which are >5mm (pre-pubertal) and >15mm (post -pubertal)
2 2 or more neurofibromas
3 freckling in armpit or groin
4 optic glioma
5 2 or more lisch nodules
6 first degree relative with NF1
what are the diagnostic criteria for NF 2
diagnosis is made if either of the following is found
1 bilateral vestibular schwannomas on imaging
2 first degree relative with NF2 and either
-unilateral vestibular schwannoma
-or neurofibroma/juvenile cataract
