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.
Phakomatoses, also known neurocutaneous syndromes, are a group of multisystemic diseases that most prominently affect structures primarily derived from the ectoderm such as the central nervous system, skin and eyes. The majority of phakomatoses are single-gene disorders that may be inherited in an autosomal dominant, autosomal recessive or X-linked pattern. Presentations may vary dramatically between patients with the same particular syndrome due to mosaicism, variable expressivity, and penetrance.Many phakomatoses are caused by mutations which alter functioning of the RAS–mitogen-activated protein kinase (MAPK) pathway that regulates cellular growth, differentiation, proliferation and death. This results in a tendency for individuals with these mutations to develop various types of benign or malignant tumors depending on the particular mutation. The presence of these tumors may result in functional and/or cosmetic problems depending on their type and location. History
The term phakomatosis originated in 1923, when the Dutch ophthalmologist van der Hoeve used the term phakoma to refer to a "mother spot" or birthmark, a physical characteristic common to patients with tuberous sclerosis and neurofibromatosis that he examined. The term phakomatoses was derived from phakos, the Greek term for birthmark. He originally used the phrase to describe two diseases: neurofibromatosis and tuberous sclerosis. This term later became imprecise when van der Hoeve also used it to include those with Sturge-Weber syndrome as they do not have similar lesions on the skin. In addition, the term phakomatosis makes no reference to the central nervous system involvement.