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Neurofibromatosis

Neurofibromatosis is an autosomal dominant condition resulting in the growth of nerve tumours

Suggested approach to neurofibromatosis type 1 osce station

Describing lesions

  • Neurofibromas
    • ‘There are multiple, well-demarcated brown circular nodules and papules present across the back in a generalized distribution.’          
    • ‘There are no secondary features (such as crusting, scaling or erosion).’
    • ‘On palpation, these lesions are soft and non-tender, with some exhibiting the button-hole sign.’
    • ‘These lesions are consistent with neurofibromas.’
  • Café au lait spots
    • ‘There are also irregularly shaped, evenly pigmented, flat brown patches.’
    • ‘These are characteristic of café au lait spots.’
  • Other areas
    • ‘I would like to look for axillary and inguinal freckling, and abdominal scars (e.g. for phaeochromocytoma surgery).’
  • Conclusion
    • ‘Given there are 2 or more neurofibromas and 6 or more café au lait spots, the likely diagnosis is neurofibromatosis type 1.’
    • ‘In addition to examining the rest of the skin and taking a full history, I would like to measure blood pressure, do a full neurological exam for signs of spinal cord neurofibromas, examine the eyes for signs of optic nerve gliomas, and use a slit lamp to look for Lisch nodules on the iris.’

If you are allowed to ask the patient questions

  • Family history
  • Eyes, ears, blood pressure
  • Any nerve lesions

Differential diagnosis

  • Neurofibromatosis type 2
  • Tuberous sclerosis (multi-system hamartoma formation)

Types of neurofibromatosis

Type 1 (peripheral) – most common

  • NF-1 gene defect (chromosome 17) resulting in peripheral neurofibromas (i.e. in skin or subcutaneous tissue)
  • Skin
    • Neurofibromas (2 or more): well-demarcated nodules which are erythematous and varied in size and shape 
    • Café au lait spots (6 or more): flat patch of asymmetrical darkened skin (brown/black)
    • Axillary freckling
  • Other features
    • Optic nerve glioma → non-correctable visual loss
    • Lisch nodules (iris hamartomas, i.e. brown spots on iris seen with slit lamp)
    • Dorsal root spinal cord tumours
    • Plexiform neurofibromas (diffuse and invasive → bony erosion)

Type 2 (central)

  • Merlin protein gene defect (chromosome 22) resulting in central schwannomas
  • Most common presenting condition is bilateral acoustic neuromas (CN8) causing hearing loss, typically at 20-30 years of age
  • Other conditions include: meningiomas, gliomas, juvenile cataracts
  • Other symptoms include: headache, balance loss, vertigo, facial weakness, deafness, tinnitus
  • Skin symptoms uncommon

Investigations

  • Diagnosed on clinical features and MRI

Management

  • Lifelong annual monitoring: vision, heart and blood pressure, hearing
  • Treat complications
  • Education
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