Neurofibromatosis Type 2 Causes and Diagnosis

Neurofibromatosis type 2 is a genetic disorder characterized by the growth of benign tumors along nerves.

In around half of cases, the genetic mutation for this condition is inherited by a child from one of their parents. In the other half of cases, the mutation arises completely sporadically and cannot be explained by any family history of the condition.

Genes associated with neurofibromatosis type 2

The gene that becomes mutated in the case of neurofibromatosis type 2 (NF2) is a tumour suppressor gene present on the long arm of chromosome 22(22q12.2). This NF2 gene codes for a protein called merlin, which is involved in regulating nerve growth. When this gene is mutated, the merlin protein produced is incomplete or even absent meaning uncontrolled growth of the nerve tissue ensues.

In cases where the condition is inherited, only one parent needs to carry the mutated gene for their offspring to be at risk of also developing the condition. If on parent has the condition, each child is at a 50% risk of developing the illness. This pattern of inheritance is referred to as autosomal dominant. The risk of developing the condition is equal between both genders.

In sporadic cases, the mutation seems to occur in either the sperm or ovum prior to conception and it is unclear why this occurs. A person who develops a sporadic NF2mutation can also pass the condition onto their offspring.

Diagnosis

Diagnosis is made based on clinical features, magnetic resonance imaging, hearing tests, vision tests and genetic testing for the NF2 mutation.

Prenatal testing can also be performed to check for this mutation and the most commonly used tests include chorionic villus sampling and amniocentesis.