Neurofibromatosis Type I
- Autosomal dominant disorder marked by tumors, cognitive deficits, and scoliosis
- Mutation in chromosome 17 responsible for control of cell division
- 50% of cases familial, 50% sporadic
- Non-malignant growths on iris called Lisch nodules present in 100% of cases by age 20
- Optic nerve and chiasm gliomas ("juvenile pilocytic astrocytomas") present in 15% of cases
- Neurofibromas cause ptosis or proptosis
- Lisch nodules: tan mounds on iris surface
- Present in 50% of cases by age 6 and 100% by age 20
- Hard to recognize without slit lamp biomicroscopy
- Do not affect vision
- Optic nerve gliomas discovered incidentally on imaging or by causing impaired vision or proptosis
- Neurofibromas grow as lumps on lids or cause proptosis
- Sphenoid dysplasia may cause pulsating eye
- Trabecular meshwork dysplasia may cause glaucoma
- Iris nevi mimic Lisch nodules, but are usually darker
- Optic nerve meningiomas or schwannomas mimic gliomas
- Many kinds of lid masses mimic neurofibromas
- For suspected neurofibromatosis type 1, refer to ophthalmologist non-urgently for detection of Lisch nodules
- For impaired vision in patient with neurofibromatosis, refer to ophthalmologist non-urgently to rule out optic glioma
- For lid mass or proptosis in patient with neurofibromatosis, refer to ophthalmologist to rule out neurofibroma
- Lisch nodules valuable in diagnosis because highly specific and present in high proportion of cases
- Optic gliomas elicit treatment with chemotherapy if vision severely impaired or worsening, but...
- Spontaneous improvement in vision may occur, and...
- Efficacy of chemotherapy not rigorously verified
- Reversal of vision loss with treatment rare
- Neurofibromas treated by surgical excision, but...
- Complete excision is difficult and dangerous
- Open-angle glaucoma must be excluded