Neurofibromatosis

Question 1

1) What is neurofibromatosis?
2) What are the 2 variations of neurofibromatosis, and which of these is the most common?

Answer 1

1) Genetic condition that causes benign nerve tumours (neuromas) to develop throughout the nervous system
2) Type 1 and type 2 - type 1 is the most common

Question 2

1) What chromosome is neurofibromatosis type 1 gene is found on?
2) What is the pattern of inheritance of neurofibromatosis?

Answer 2

1) 17
2) Autosomal dominant

Question 3

Name 2 features of neurofibromatosis type 1

Answer 3

• Cafe-au-lait spots: flat, coffee coloured patches of skin seen in 1st year of life
• Axillary or inguinal freckles
• Iris hamartomas (Lisch nodules): yellow brown spots on the iris
• Nodular neurofibromas that arise from nerve trunks

Question 4

Diagnosis is based on clinical features. There must be at least 2 of the 7 features (CRABBING mnemonic to indicate a diagnosis - name 3 of these features.

Answer 4

C – Café-au-lait spots (6 or more) measuring ≥ 5mm in children or ≥ 15mm in adults
R – Relative with NF1
A – Axillary or inguinal freckles
BB – Bony dysplasia such as Bowing of a long bone or sphenoid wing dysplasia
I – Iris hamartomas (Lisch nodules) (2 or more)
N – Neurofibromas (2 or more) or 1 plexiform neurofibroma
G – Glioma of the optic nerve

Question 5

How is it managed?

Answer 5

Control symptoms, monitor the disease and treat complications

Question 6

Name 3 complications of neurofibromatosis

Answer 6

• Migraines
• Epilepsy
• Renal artery stenosis causing hypertension
• Learning and behavioural problems i.e. ADHD
• Scoliosis of the spine
• Vision loss (secondary to optic nerve gliomas)
• Malignant peripheral nerve sheath tumours
• Gastrointestinal stromal tumour (a type of sarcoma)
• Brain tumours
• Spinal cord tumours with associated neurology (e.g. paraplegia)
• Increased risk of cancer (e.g. breast cancer)
• Leukaemia

Question 7

1) What chromosome is the neurofibromatosis type 2 gene is found on?
2) The gene codes for a protein called merlin, which is a tumour suppressor protein particularly important in what type of cell?
3) What does mutation of this gene result in?
4) What is the inheritance pattern?

Answer 7

1) 22
2) Schwann cells
3) Development of schwannomas
4) Autosomal dominant

Question 8

What is neurofibromatosis type 2 most associated with?

Answer 8

Acoustic neuromas

Question 9

Name 2 symptoms associated with acoustic neuromas

Answer 9

• Hearing loss
• Tinnitus
• Balance problems