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Schwannoma – Antoni A and B – very high mag. Micrograph of a schwannoma, a tumor seen in neurofibromatosis type II. NF-2 may be inherited in an autosomal dominant fashion, as well as through random mutation. NF II is a microdeletion syndrome involving mutations in the NF2 gene located at 22q12. It is an inheritable disorder with an autosomal dominant mode of transmission.
NF II is caused by a defect in the gene that normally gives rise to a product called Merlin or Schwannomin, located on chromosome 22 band q11-13. This peptide is thought to have a tumor-suppressive function. The so-called acoustic neuroma of NF II is in fact a schwannoma of the nervus vestibularis, or vestibular schwannoma. The misnomer of acoustic neuroma is still often used.
Many people with NF II were included in studies that were designed to compare disease type and progression with exact determination of the associated mutation. The goal of such comparisons of genotype and phenotype is to determine whether specific mutations cause respective combinations of symptoms. This would be extremely valuable for the prediction of disease progression and the planning of therapy starting at a young age. In most cases the mutation in the NF II gene causes shortened peptides. Patients with frameshift mutations or nonsense mutations suffer poor prognosis. Patients with missense mutations have a better prognosis.
In cases with mutations in the splice-acceptor-region, there is no good correlation to determine. Point mutations may have only minor effects. Cases are published in which exactly the same mutation is associated with clearly different outcome. Bilateral vestibular schwannomas are diagnostic of NF2. Two or more meningioma plus unilateral VS or any two of glioma, schwannoma and cataract. First degree relative with NF II and the occurrence of juvenile posterior subcapsular cataract.