Less than 10% with neuroendocrine tumors will develop metastases. Genetics
The majority of neurocutaneous syndromes are single-gene disorders however they are caused by different genes and have different inheritance patterns. For instance, neurofibromatosis 1 and 2, Tuberous sclerosis complex, Von Hippel-Lindau syndrome and Legius syndrome are inherited in an autosomal dominant manner. Incontinentia pigmenti is X-linked dominant and Sturge-Weber syndrome is sporadic. Some neurocutaneous disorders are found exclusively as mosaics such as Sturge-Weber syndrome and Proteus syndrome. Others such as neurofibromatosis type 1 and 2 as well as tuberous sclerosis complex can potentially be mosaics but may not be. Mosaicism may be suspected in cases with either a mild or incomplete presentation of a neurocutaneous disorder. A definitive diagnosis is most likely to be obtained if testing of affected tissues is possible.Patients and families of those affected by neurocutaneous disorders often benefit from genetic counseling. It may provide an opportunity to provide a better understanding of the potential risk to future offspring as well as to improve coping with the various implications of the condition. If desired, a prenatal diagnosis can be obtained by either amniocentesis or chorionic villus sampling. Another potential option is preimplantation genetic diagnosis where an embryo that does not have the mutation can be selectively implanted into the mother. Diagnosis
Many neurocutaneous syndromes have established diagnostic criteria which may facilitate a diagnosis without necessarily requiring genetic testing. For instance, neurofibromatosis types 1 and 2, tuberous sclerosis complex and incontinentia pigmenti have formal diagnostic criteria.
They often do not cause additional morbidity but may in up to one-half of patients. Neurocognitive impairment, attention-deficit hyperactivity disorder,  autism spectrum disorder and behavioral disorders are also commonly seen in patients with neurofibromatosis type 1. Epilepsy is seen in 4-7% of patients.Musculoskeletal system manifestations can develop in patients with neurofibromatosis type 1. Common findings include sphenoid wing dysplasia, osteopenia, osteoporosis, anterior chest wall deformities as well as scoliosis. Patients are at a much greater risk for fractures than the general population.Vascular abnormalities are also frequently encountered in patients with neurofibromatosis type 1. These may include renal artery stenosis, pulmonary artery stenosis, cerebral artery stenosis and aneurysms. Complications may include myocardial infarction and stroke. Relative to the general population the risk for certain types of cancer is increased significantly. For instance, the risk for brain tumors and breast cancer is increased by 5 times. Neurofibromatosis Type II
Neurofibromatosis type 2 is an autosomal dominant condition that affects approximately 1 in 35,000-40,000 people. It is caused by mutations in the NF2 gene on chromosome 22 which has a high penetrance though most patients do not present with symptoms until adulthood. Approximately half of patients have de novo mutations and as many as 59.7% are mosaic. Patients who present in childhood tend to have a more severe phenotype.Bilateral vestibular schwannomas are the most characteristic finding and in the vast majority of cases are benign. However, they are responsible for significant morbidity and are responsible for the most common presenting symptom of hearing loss in adults.