Certain eunuchs, such as the Ming dynasty official Zheng He, gained immense power that occasionally superseded that of even the Grand Secretaries. Self-castration was a common practice, although it was not always performed completely, which led to it being made illegal. It is said that the justification for the employment of eunuchs as high-ranking civil servants was that, since they were incapable of having children, they would not be tempted to seize power and start a dynasty. In many cases, eunuchs were considered more reliable than the scholar-officials. As a symbolic assignment of heavenly authority to the palace system, a constellation of stars was designated as the Emperors, and, to the west of it, four stars were identified as his "eunuchs. "The tension between eunuchs in the service of the emperor and virtuous Confucian officials is a familiar theme in Chinese history. In his History of Government, Samuel Finer points out that reality was not always that clear-cut. There were instances of very capable eunuchs who were valuable advisers to their emperor, and the resistance of the "virtuous" officials often stemmed from jealousy on their part. Ray Huang argues that in reality, eunuchs represented the personal will of the Emperor, while the officials represented the alternative political will of the bureaucracy. The clash between them would thus have been a clash of ideologies or political agenda.The number of eunuchs in Imperial employ fell to 470 by 1912, when the practice of using them ceased. The last Imperial eunuch, Sun Yaoting, died in December 1996.
Cause
The three types of Neurofibromatosis are caused by different mutations on chromosomes. NF1 is caused by a mutation on the NF1 gene on the arm of chromosome 17. NF2 is caused by a mutation on the NF2 tumor suppressor gene on chromosome 22. Schwannomatosis is caused by various mutations on chromosome 22.Neurofibromatosis is an autosomal dominant disorder, which means only one copy of the affected gene is needed for the disorder to develop. If one parent has neurofibromatosis, his or her children have a 50% chance of developing the condition as well. The severity of the parents condition does not affect the child; the affected child may have mild NF1 even though it was inherited from a parent with a severe form of the disorder. The types of neurofibromatosis are:

Neurofibromatosis type I, in which the nerve tissue grows tumors (neurofibromas) that may be benign, but may cause serious damage by compressing nerves and other tissues. Neurofibromatosis type II, in which bilateral acoustic neuromas (tumors of the vestibulocochlear nerve or cranial nerve 8 (CN VIII) also known as schwannoma) develop, often leading to hearing loss. Schwannomatosis, in which painful schwannomas develop on spinal and peripheral nerves. Pathophysiology
Neurofibromatosis type I is caused by a mutation on chromosome 17 encoding a cytoplasmic protein known as neurofibromin. This protein is a tumor suppressor and therefore serves as a signal regulator of cell proliferation and differentiation. A dysfunction or lack of neurofibromin can affect regulation, and cause uncontrolled cell proliferation, leading to the tumors (neurofibromas) that characterize NF1.