Timothy C. Hain, MD • Page last modified: August 22, 2020Neurofibromatosis is the name given to two distinct genetic disorders characterized by cutaneous tumors, or neurofibromas.
Neurofibromatosis type 1, or NF1, occurs in 1 in 3000 individuals. It is the result of a genetic defect in chromosome 17. About half of all cases are inherited in an autosomal dominant fashion, and the other half are sporadic. Typical manifestations include:
- cafe au lait spots
- cutaneous tumors
- plexiform lesions
- axillary freckling
- Lisch nodules of the iris
- Optic gliomas
- Bony abnormalitie
NF2 is rare; there are only several thousand affected individuals in the entire United States, corresponding to about 1 in 40,000 individuals. Roughly 5% of patients with acoustic neuroma have type II neurofibromatosis. More information about NF2 can be found at https://ghr.nlm.nih.gov/gene=nf2. NF-2 is inherited in an autosomal dominant fashion. The defect in NF-2 is in chromosome 22.
Criteria for diagnosis of NF-2 include:
1) bilateral acoustic neuromas, or 2) first-degree relative with NF-2 and either a unilateral lesion, or two of the following: neurofibroma, meningioma, glioma, schwannoma, and a juvenile posterior subcapsular opacity.
|Axial image of patient with NF2 showing acoustic neuromas on both sides (Image courtesy of Dr. Richard Wiet).||Higher image showing multiple meningiomas in same patient with NF2.|
Acoustic neuroma caused by type-II neurofibromatosis should be suspected in young patients and those with a family history of neural tumors. The figure above shows an example of such a person. It is common in this disease to become deaf due to bilateral acoustic neuromas. Genetic testing for NF1 and NF2 is available commercially, for example, from Athena Diagnostics. (https://www.athenadiagnostics.com)
Treatment of acoustic neuromas associated with neurofibromatosis generally follows the same principles as treatment of acoustic neuroma that arise sporadically. As tumors are usually multiple, and may arise on the opposite side, there is an attempt to do as little damage as possible.
Recent reports suggest that NF2 may be treated medically with bevacizumab, an antibody to vascular endothelial growth factor (VEGF) (Plotkin et al, 2009; Sverak et al, 2018). We hope that this treatment method is confirmed to be effective as well as financially feasible. Most treatments with monoclonal antibodies are extremely expensive.