Depends. Neurofibromatosis comes in many forms and involvement. If the neurofibromas affect critical areas of function. Death is possible. Forinstance if tumor becomes so enlarged that compresses airway or blood vessels supplying blood to brain or other vital organs. In rare insances malikgnent degeneration of neurofibromas into neuofibrosarcomas can occur. Some patients develop other lethal tumors..
Very rare. You can develop neurofibroma in the chest. Occasionally the tumor can undergo malignant transformation. Any rapid increase in size should cause concern.
No and yes. Depending on the location eg sudden hemorrhage in tumor in brain-rare possibility. Continuous non treatable seizure. It is not like heart attack.