Neurofibromatosis

Question 1

def

Answer 1

an autosomal dominant genetic disorder affecting cells of the neural crest, resulting in the development of multiple neurocutaneous tumours

Question 2

what are the two types of neurofibromatosis

Answer 2

1 Type 1 NF (von Recklinghausens disease)

2. Type 2 NF

Question 3

what is Type 1 NF (von Recklinghausens disease)

Answer 3

characterised by:
1 many cafe-au-lait spots
2 freckling (axillary/inguinal)
3 neurofibromas
4 lisch nodules

Question 4

what is Type 2 NF

Answer 4

characterised by:
1 few cafe-au-lait spots
2 bilateral vestibular schwannomas
3 juvenile posterior subcapsular lenticular opacity (cataract)

Question 5

aetiology of Type 1 NF (von Recklinghausens disease)

Answer 5

mutation in NF1 gene which encodes neurofibromin (GTPase activating protein)
this results in excess activity of proto-oncogene p21-ras

Question 6

which chromosome is NF1 gene found on

Answer 6

17

Question 7

aetiology of Type 2 NF

Answer 7

mutations in NF2 gene which encords merlin (or schwannomin)

Question 8

which chromosome is NF2 gene found on1

Answer 8

22

Question 9

epi

Answer 9

NF1>NF2

no gender or racial predilection

Question 10

risk factors for NF

Answer 10

parent with NF

Question 11

history of Type 1 NF (von Recklinghausens disease)

Answer 11

1 skin lesions
2 learning difficulties (common)
3 visual disturbances (optic gliomas)
4 precocious puberty

Question 12

why might precocious puberty occur in Type 1 NF (von Recklinghausens disease)

Answer 12

lesions in the pituitary may occur due to optic glioma involving the chiasm

Question 13

history of Type 2 NF

Answer 13

1 hearing loss or tinnitus (ringing in ears)
2 balance problems
3 facial pain/numbness

Question 14

examination of Type 1 NF (von Recklinghausens disease)

Answer 14

1 cafe-au-lait spots
2 freckling (armpit/groin)
3 neurofibromas
4 lisch nodules

Question 15

what are cafe-au-lait spots

Answer 15

flat coffee coloured patches of skin seen in 1st year of life

Question 16

when does freckling in Type 1 NF usually present

Answer 16

by 10yrs

Question 17

what are neurofibromas

Answer 17

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

Question 18

what are lisch nodules

Answer 18

small regular brown or translucent mounds (hamartomas) on the iris

aggregation of dendritic melanocytes

Question 19

examination of Type 2 NF

Answer 19

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

Question 20

investigations

Answer 20

1 opthalmological assessment
2 audiometry
3 MRI brain + spinal cord
-for vestibular schwannomas, meningiomas, nerve root neurofibromas

Question 21

what are the diagnostic criteria for NF 1 (von Recklinghausens disease)

Answer 21

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

Question 22

what are the diagnostic criteria for NF 2

Answer 22

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