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Neurofibromatosis type 2
Neurofibromatosis type 2 (NF2) is a tumor-prone disorder characterized by the development of multiple schwannomas and meningiomas.
Prevalence (initially estimated at 1: 200,000) is around 1 in 60,000.
Affected individuals inevitably develop schwannomas, typically affecting both vestibular nerves and leading to hearing loss and deafness. The majority of patients present with hearing loss, which is usually unilateral at onset and may be accompanied or preceded by tinnitus. Vestibular schwannomas may also cause dizziness or imbalance as a first symptom. Nausea, vomiting or true vertigo are rare symptoms, except in late-stage disease. The other main tumors are schwannomas of the other cranial, spinal and peripheral nerves; meningiomas both intracranial (including optic nerve meningiomas) and intraspinal, and some low-grade central nervous system malignancies (ependymomas). Ophthalmic features are also prominent and include reduced visual acuity and cataract. About 70% of NF2 patients have skin tumors (intracutaneous plaque-like lesions or more deep-seated subcutaneous nodular tumors).
NF2 is caused by mutations in the NF2 gene on chromosome 22. More than 50% of patients represent new mutations and as many as one-third are mosaic for the underlying disease-causing mutation. Although truncating mutations (nonsense and frameshifts) are the most frequent germline event and cause the most severe disease, single and multiple exon deletions are common. A strategy for detection of the latter is vital for a sensitive analysis.
Diagnosis is based on clinical and neuroimaging studies. Presymptomatic genetic testing is an integral part of the management of NF2 families.
The main differential diagnosis of NF2 is schwannomatosis.
Prenatal diagnosis and pre-implantation genetic diagnosis is possible.
NF2 is a dominantly inherited tumor predisposition syndrome.
Management and treatment
NF2 represents a difficult management problem with most patients facing substantial morbidity and reducedlife expectancy. Surgery remains the focus of current management although watchful waiting with careful surveillance and occasionally radiation treatment have a role.
Prognosis is adversely affected by early age at onset, a higher number of meningiomas and having a truncating mutation.