Neurofibromatosis - External and Internal Eye
Affecting 1 in 3000, NF1 is characterized by hallmark cutaneous, neurologic, bone, soft tissue, and ophthalmologic findings resulting from deregulated growth of neural crest origin cell lines.
Although 100% penetrant by age 5 years and though a third of affected patients will develop serious complications, NF1's diverse expression makes prognostic information difficult to deliver to patients. About 50% of the cases are familial, with an autosomal dominant expression pattern, and 50% of cases arise from de novo mutations.
Neurofibromatosis is clinically diagnosed via the presence of 2 or more of the following:
- Six or more café-au-lait macules greater than 5 mm in prepubertal individuals and greater than 15 mm in diameter in postpubertal individuals
- Two or more Lisch nodules (iris hamartomas)
- Two or more neurofibromas of any type or a single plexiform neurofibroma
- Freckling in the axillary or inguinal region (intertriginous)
- Optic nerve glioma (in early childhood)
- Distinctive osseus dysplasia (such as sphenoid or tibial)
- A first-degree relative with NF1
Other malignancies and tumors associated with neurofibromatosis include pheochromocytomas, meningiomas, sarcomas, and gastrointestinal tumors of neuroendocrine origin. Patients may have learning disabilities (30%-50%), skeletal abnormalities, vasculopathies, and endocrinologic abnormalities.
Prompt ophthalmologic screening in patients with café-au-lait macules is recommended to diagnose NF1 and help prevent vision loss.
- Optic nerve gliomas are grade 1 pilocytic astrocytomas in NF1 that affect the optic nerve, chiasm, or optic tract. They are the most common intraorbital or cranial manifestation of neurofibromatosis, affecting 30%-40% of patients. Often asymptomatic, they are slow growing, locally invasive, and can progress to produce significant morbidity though rarely mortality. Isolated asymptomatic optic nerve gliomas discovered during screening carry the best prognosis. Involvement of the chiasm, pulsatile proptosis, or extension along the visual pathway carries an unfavorable prognosis. Pulsatile proptosis, or the "Orphan Annie sign," is caused by absence of the sphenoid wing with a herniated encephalocele.
- Orbitofacial plexiform neurofibromas are in seen in 1%-4% of children with NF1. These are variants of benign peripheral nerve sheath tumors that form tangles of unencapsulated, highly vascular, and infiltrative neural tissue involving the eyelids, temporal region, and orbit and causing physical disfiguration, asymmetric refractive error, and mechanical ptosis with a high incidence of resultant amblyopia. They may degenerate into malignant peripheral nerve sheath tumors such as neurofibrosarcomas. Plexiform neurofibromas of the upper eyelid can be associated with ipsilateral glaucoma.
NF2, or central neurofibromatosis, is 10 times less common than NF1 and primarily presents with acoustic neuromas (schwannomas of the 8th cranial nerve). NF2 presents with fewer café-au-lait macules, rarely forms Lisch nodules of the iris, and is primarily associated ophthalmologically with juvenile cataracts. Optic nerve meningiomas, retinal hamartomas, and epiretinal membranes are also associated with NF2, and any child with decreased vision or retinal exam abnormalities should undergo ophthalmologic evaluation to distinguish NF1 and NF2 from retinoblastoma.
Q85.01 – Neurofibromatosis, type 1
Q85.02 – Neurofibromatosis, type 2
19133005 – Neurofibromatosis syndrome
Other conditions with café-au-lait macules:
- Legius syndrome – Autosomal dominant NF1-like syndrome with loss of function of Ras regulatory gene Spred1 with café-au-lait macules, axillary freckling, and macrocephaly but lacks neurofibromas and CNS tumors.
- Constitutional mismatch repair-deficiency syndrome – Homozygous deficiency in 1 of the 4 mismatch repair proteins results in café-au-lait macules and axillary freckling but presents primarily with hematologic malignances in childhood followed by glioblastomas and colorectal cancer.
- Noonan syndrome – Characterized by short stature, webbed neck, pulmonic stenosis, and café-au-lait macules without axillary freckling or Lisch nodules.
- McCune-Albright syndrome – Premature puberty, bony abnormalities, and large café au lait macules with irregular outline.
- Other forms of neurofibromatosis, including NF2
- Brainstem gliomas
- Cauda equina and conus medullaris syndromes
- Low-grade astrocytoma
- Spinal cord hemorrhage or infarction
- Spinal epidural abscess
The differential diagnosis for NF2 includes: