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SPRING 2026 InTouch | 17 Continued over ... WHAT IS NEUROFIBROMATOSIS TYPE 1? There are two other forms of neurofibromatosis which are different from NF1 - NF2 and Schwannomatosis. NF2 usually first presents in teenage or early 20s with bilateral acoustic neuromas and is associated with a variety of benign brain and spinal tumours including meningiomas, cataracts and only occasional skin manifestations. Schwannomatosis is characterised by multiple schwannomas (benign nerve sheath tumor) of cranial, spinal and peripheral nerves which can be very painful but which are not associated with the ocular auditory or skin changes of NF2. The cause of Neurofibromatosis type 1 Neurofibromatosis is caused by mutations in the neurofibromin gene on chromosome 1. This protein is produced in many cells, including nerve cells and specialized cells surrounding nerves (oligodendrocytes and Schwann cells). Neurofibromin acts as a tumor suppressor, which means that it keeps cells from growing and dividing too rapidly or in an uncontrolled way. Mutations in the NF1 gene lead to the production of a nonfunctional version of neurofibromin that cannot regulate cell growth and division. This allows tumors such as neurofibromas to form along nerves throughout the body. It is unclear how mutations in the NF1 gene lead to the other features of NF1, such as café-au-lait spots and learning disabilities. About 50% of cases are caused by a spontaneous mutation in the gene (de novo), usually the paternal copy, and in these cases there is no family history of the condition. Occasionally in NF1 only a proportion of the body is involved - segmental NF – this is due to somatic mosaicism (different genetic information in the same tissue) so the mutation is only present in a proportion of cells. Someone with NF1 has a 50% risk of passing on the condition each time they have a child. It is a very variable condition within as well as between families but does not skip generations. This means that children in the same family can have different presentations from each other and these may be different again from another unrelated family’s presentation of the condition. The reoccurrence risk for segmental NF will depend on whether the germ cells in the ovary or testes are involved. Genetic testing is possible but is usually only done if a family Autosomal dominant Unaffected mother Affected Unaffected Affected father Unaffected child Unaffected child Affected child Affected child Mode of inheritance. are considering prenatal or pre- implantation diagnosis or if an early definite diagnosis is critical and the person thought to be affected does not yet fulfil clinical criteria. Someone with NF1 has a 50% risk of passing on the condition each time they have a child. It is a very variable condition within as well as between families but does not skip generations. Neurofibromatosis Type 1 Normal Schwann Cell Neurofibroma Plexiform neurofibroma