Because they are genetic disorders, NF is inherited and is not catching. However, some cases are de novo, meaning that the mutation occurs newly in a developing individual and was not present in the parents of the individual. It is caused by mutations of specific genes that leads to growth of various nerve tissue tumors, some of which are called neurofibromas, hence the name of the condition. The tumors associated with NF are typically benign.
NF is autosomal dominant, which means that an individual only needs to have one copy of the abnormal gene to have the disorder.
Although the name of this disease is related to its nervous system origin, the mutations cause problems in all cells that are derived from neural crest cells in early development. This includes cell types specific to the nervous system such as Schwann cells (which produce the myelin sheath that insulates many nerve fibers in peripheral nerves) but can also involve melanocytes and endoneurial fibroblasts.
NF 1 is the most common type and usually presents with numerous neurofibromas, tumor nodules that occur under the skin. The disease can also cause other skin lesions including freckling of the groin and arm pit, "café au lait spots" (pigmented birth marks on the skin), skeletal abnormalities, optic nerve glioma (a tumor of the nerve from the eye) and other manifestations. Other nervous system related tumors, such as other gliomas and pheochromocytoms, can also occur in multiple locations.
Neurofibromatosis type 2 is less common, accounting for about 10% of all cases of NF. The skin lesions of NF 1 are not typical of NF 2, which presents more commonly with schwannomas, in particular schwannomas of the vestibular nerves coming from the inner ear to the brain stem. These vestibular schwannomas, or acoustic neuromas, are relatively rare in the general population but are common in individuals with NF 2 and can occur bilaterally (on both sides). Other tumors that are associated with nervous system structures or its surroundings can occur as well, including meningiomas and ependymomas. Because these tumor types commonly affect the intracranial space (inside the skull or cranium), NF 2 is sometimes referred to as "central neurofibromatosis". These central tumors can cause a number of different types of symptoms, depending on their type, size and location. The acoustic neuromas most commonly cause headache as well as hearing loss and/or tinnitus (ringing in the ears) on the affected side.
Other types of NF are much more rare than types 1 and 2. Each has slightly different, but similar, types of presenting symptoms and tumors that can occur.
Diagnosis may also include any number of imaging studies (CT, MRI, etc.) to identify tumors that are associated with the disease. These may be ordered to work-up a symptom the patient is experiencing or as a screening test in those who are not yet symptomatic but known to have the disease.
Prenatal testing for the disorder is also available for parents who have a personal history of the disease. This can typically be done through chorionic villus sampling or amniocentesis.
Generally, the tumors associated with NF are benign. However, because of their location in and around nerves and, in the case of NF 2, in or near the brain, these tumors can compress nearby nervous system structures and cause damage or dysfunction. Rarely, malignant (cancerous) tumors can occur in some patients.