Neurofibromatosis (NF) is a group of three conditions in which tumors grow in the nervous system. The three types are neurofibromatosis type I (NF1), neurofibromatosis type II (NF2), and schwannomatosis. In NF1 symptoms include light brown spots on the skin, freckles in the armpit and groin, small bumps within nerves, and scoliosis. In NF2, there may be hearing loss, cataracts at a young age, balance problems, flesh colored skin flaps, and muscle wasting. In schwannomatosis there may be pain either in one location or in wide areas of the body. The tumors in NF are generally non-cancerous.The cause is a genetic mutation in certain oncogenes. These can be inherited from a persons parents, or in about half of cases spontaneously occur during early development. Different mutations result in the three types of NF. Neurofibromatosis arise from the supporting cells of the nervous system rather than the neurons themselves. In NF1, the tumors are neurofibromas (tumors of the peripheral nerves), while in NF2 and schwannomatosis tumors of Schwann cells are more common. Diagnosis is typically based on symptoms, examination, medical imaging, and biopsy. Genetic testing may rarely be done to support the diagnosis.There is no known prevention or cure. Surgery may be done to remove tumors that are causing problems or have become cancerous. Radiation and chemotherapy may also be used if cancer occurs.
alpha blockers), autonomic neuropathy, decreased blood volume, multiple system atrophy,  and age-related blood-vessel stiffness. Apart from addressing the underlying cause, orthostatic hypotension may be treated with a recommendation to increase salt and water intake (to increase the blood volume), wearing compression stockings, and sometimes medication (fludrocortisone, midodrine, or others). Salt loading (dramatic increases in salt intake) must be supervised by a doctor, as this can cause severe neurological problems if done too aggressively. Signs and symptoms
Orthostatic hypotension is characterized by symptoms that occur after standing (from lying or sitting), particularly when done rapidly. Many report lightheadedness (a feeling that one might be about to faint), sometimes severe, or even actual fainting with associated fall risk. With chronic orthostatic hypotension, the condition and its effects may worsen even as fainting and many other symptoms become less frequent. Generalized weakness or tiredness may also occur. Some also report difficulty concentrating, blurred vision, tremulousness, vertigo, anxiety, palpitations (awareness of the heartbeat), unsteadiness, feeling sweaty or clammy, and sometimes nausea. A person may look pale. Some people may experience severe orthostatic hypotension with the only symptoms being confusion or extreme fatigue. Chronic severe orthostatic hypotension may present as fluctuating cognition/delirium. Women who are pregnant are also susceptible to orthostatic hypotension. Associated diseases
The disorder may be associated with Addisons disease, atherosclerosis (build-up of fatty deposits in the arteries), diabetes, pheochromocytoma, porphyria, and certain neurological disorders, including  autoimmune autonomic ganglionopathy, multiple system atrophy, and other forms of dysautonomia. It is also associated with Ehlers–Danlos syndrome and anorexia nervosa.