Neurofibromatosis 1: An autosomal dominant inherited disorder (with a high frequency of spontaneous mutations) that features developmental changes in the nervous system, muscles, bones, and skin, most notably in tissue derived from the embryonic NEURAL CREST. Multiple hyperpigmented skin lesions and subcutaneous tumors are the hallmark of this disease. Peripheral and central nervous system neoplasms occur frequently, especially OPTIC NERVE GLIOMA and NEUROFIBROSARCOMA. NF1 is caused by mutations which inactivate the NF1 gene (GENES, NEUROFIBROMATOSIS 1) on chromosome 17q. The incidence of learning disabilities is also elevated in this condition. (From Adams et al., Principles of Neurology, 6th ed, pp1014-18) There is overlap of clinical features with NOONAN SYNDROME in a syndrome called neurofibromatosis-Noonan syndrome. Both the PTPN11 and NF1 gene products are involved in the SIGNAL TRANSDUCTION pathway of Ras (RAS PROTEINS).Neurofibromatosis 2: An autosomal dominant disorder characterized by a high incidence of bilateral acoustic neuromas as well as schwannomas (NEURILEMMOMA) of other cranial and peripheral nerves, and other benign intracranial tumors including meningiomas, ependymomas, spinal neurofibromas, and gliomas. The disease has been linked to mutations of the NF2 gene (GENES, NEUROFIBROMATOSIS 2) on chromosome 22 (22q12) and usually presents clinically in the first or second decade of life.Genes, Neurofibromatosis 1: Tumor suppressor genes located on the long arm of human chromosome 17 in the region 17q11.2. Mutation of these genes is thought to cause NEUROFIBROMATOSIS 1, Watson syndrome, and LEOPARD syndrome.Genes, Neurofibromatosis 2: Tumor suppressor genes located on the long arm of human chromosome 22. Mutation or loss of these genes causes NEUROFIBROMATOSIS 2.Neurofibromatoses: A group of disorders characterized by an autosomal dominant pattern of inheritance with high rates of spontaneous mutation and multiple neurofibromas or neurilemmomas. NEUROFIBROMATOSIS 1 (generalized neurofibromatosis) accounts for approximately 95% of cases, although multiple additional subtypes (e.g., NEUROFIBROMATOSIS 2, neurofibromatosis 3, etc.) have been described. (From Neurochirurgie 1998 Nov;44(4):267-72)Neurofibromin 1: A protein found most abundantly in the nervous system. Defects or deficiencies in this protein are associated with NEUROFIBROMATOSIS 1, Watson syndrome, and LEOPARD syndrome. Mutations in the gene (GENE, NEUROFIBROMATOSIS 1) affect two known functions: regulation of ras-GTPase and tumor suppression.Neurofibromin 2: A membrane protein homologous to the ERM (Ezrin-Radixin-Moesin) family of cytoskeleton-associated proteins which regulate physical properties of membranes. Alterations in neurofibromin 2 are the cause of NEUROFIBROMATOSIS 2.Neurofibroma, Plexiform: A type of neurofibroma manifesting as a diffuse overgrowth of subcutaneous tissue, usually involving the face, scalp, neck, and chest but occasionally occurring in the abdomen or pelvis. The tumors tend to progress, and may extend along nerve roots to eventually involve the spinal roots and spinal cord. This process is almost always a manifestation of NEUROFIBROMATOSIS 1. (From Adams et al., Principles of Neurology, 6th ed, p1016; J Pediatr 1997 Nov;131(5):678-82)Neurofibroma: A moderately firm, benign, encapsulated tumor resulting from proliferation of SCHWANN CELLS and FIBROBLASTS that includes portions of nerve fibers. The tumors usually develop along peripheral or cranial nerves and are a central feature of NEUROFIBROMATOSIS 1, where they may occur intracranially or involve spinal roots. Pathologic features include fusiform enlargement of the involved nerve. Microscopic examination reveals a disorganized and loose cellular pattern with elongated nuclei intermixed with fibrous strands. (From Adams et al., Principles of Neurology, 6th ed, p1016)Cafe-au-Lait Spots: Light brown pigmented macules associated with NEUROFIBROMATOSIS and Albright's syndrome (see FIBROUS DYSPLASIA, POLYOSTOTIC).Optic Nerve Glioma: Glial cell derived tumors arising from the optic nerve, usually presenting in childhood.Nerve Sheath Neoplasms: Neoplasms which arise from nerve sheaths formed by SCHWANN CELLS in the PERIPHERAL NERVOUS SYSTEM or by OLIGODENDROCYTES in the CENTRAL NERVOUS SYSTEM. Malignant peripheral nerve sheath tumors, NEUROFIBROMA, and NEURILEMMOMA are relatively common tumors in this category.Neurilemmoma: A neoplasm that arises from SCHWANN CELLS of the cranial, peripheral, and autonomic nerves. Clinically, these tumors may present as a cranial neuropathy, abdominal or soft tissue mass, intracranial lesion, or with spinal cord compression. Histologically, these tumors are encapsulated, highly vascular, and composed of a homogenous pattern of biphasic fusiform-shaped cells that may have a palisaded appearance. (From DeVita Jr et al., Cancer: Principles and Practice of Oncology, 5th ed, pp964-5)Optic Nerve Neoplasms: Benign and malignant neoplasms that arise from the optic nerve or its sheath. OPTIC NERVE GLIOMA is the most common histologic type. Optic nerve neoplasms tend to cause unilateral visual loss and an afferent pupillary defect and may spread via neural pathways to the brain.Neuroma, Acoustic: A benign SCHWANNOMA of the eighth cranial nerve (VESTIBULOCOCHLEAR NERVE), mostly arising from the vestibular branch (VESTIBULAR NERVE) during the fifth or sixth decade of life. Clinical manifestations include HEARING LOSS; HEADACHE; VERTIGO; TINNITUS; and FACIAL PAIN. Bilateral acoustic neuromas are associated with NEUROFIBROMATOSIS 2. (From Adams et al., Principles of Neurology, 6th ed, p673)Peripheral Nervous System Neoplasms: Neoplasms which arise from peripheral nerve tissue. This includes NEUROFIBROMAS; SCHWANNOMAS; GRANULAR CELL TUMORS; and malignant peripheral NERVE SHEATH NEOPLASMS. (From DeVita Jr et al., Cancer: Principles and Practice of Oncology, 5th ed, pp1750-1)Neurofibrosarcoma: A malignant tumor that arises from small cutaneous nerves, is locally aggressive, and has a potential for metastasis. Characteristic histopathologic features include proliferating atypical spindle cells with slender wavy and pointed nuclei, hypocellular areas, and areas featuring organized whorls of fibroblastic proliferation. The most common primary sites are the extremities, retroperitoneum, and trunk. These tumors tend to present in childhood, often in association with NEUROFIBROMATOSIS 1. (From DeVita et al., Cancer: Principles & Practice of Oncology, 5th ed, p1662; Mayo Clin Proc 1990 Feb;65(2):164-72)Cranial Nerve Neoplasms: Benign and malignant neoplasms that arise from one or more of the twelve cranial nerves.Nervous System Neoplasms: Benign and malignant neoplastic processes arising from or involving components of the central, peripheral, and autonomic nervous systems, cranial nerves, and meninges. Included in this category are primary and metastatic nervous system neoplasms.Meningioma: A relatively common neoplasm of the CENTRAL NERVOUS SYSTEM that arises from arachnoidal cells. The majority are well differentiated vascular tumors which grow slowly and have a low potential to be invasive, although malignant subtypes occur. Meningiomas have a predilection to arise from the parasagittal region, cerebral convexity, sphenoidal ridge, olfactory groove, and SPINAL CANAL. (From DeVita et al., Cancer: Principles and Practice of Oncology, 5th ed, pp2056-7)Auditory Brain Stem Implants: Multi-channel hearing devices typically used for patients who have tumors on the COCHLEAR NERVE and are unable to benefit from COCHLEAR IMPLANTS after tumor surgery that severs the cochlear nerve. The device electrically stimulates the nerves of cochlea nucleus in the BRAIN STEM rather than the inner ear as in cochlear implants.Meningocele: A congenital or acquired protrusion of the meninges, unaccompanied by neural tissue, through a bony defect in the skull or vertebral column.Hamartoma: A focal malformation resembling a neoplasm, composed of an overgrowth of mature cells and tissues that normally occur in the affected area.Pseudarthrosis: A pathologic entity characterized by deossification of a weight-bearing long bone, followed by bending and pathologic fracture, with inability to form normal BONY CALLUS leading to existence of the "false joint" that gives the condition its name. (Dorland, 27th ed)Chromosomes, Human, Pair 17: A specific pair of GROUP E CHROMOSOMES of the human chromosome classification.Schwann Cells: Neuroglial cells of the peripheral nervous system which form the insulating myelin sheaths of peripheral axons.Learning Disorders: Conditions characterized by a significant discrepancy between an individual's perceived level of intellect and their ability to acquire new language and other cognitive skills. These disorders may result from organic or psychological conditions. Relatively common subtypes include DYSLEXIA, DYSCALCULIA, and DYSGRAPHIA.Noonan Syndrome: A genetically heterogeneous, multifaceted disorder characterized by short stature, webbed neck, ptosis, skeletal malformations, hypertelorism, hormonal imbalance, CRYPTORCHIDISM, multiple cardiac abnormalities (most commonly including PULMONARY VALVE STENOSIS), and some degree of INTELLECTUAL DISABILITY. The phenotype bears similarities to that of TURNER SYNDROME that occurs only in females and has its basis in a 45, X karyotype abnormality. Noonan syndrome occurs in both males and females with a normal karyotype (46,XX and 46,XY). Mutations in a several genes (PTPN11, KRAS, SOS1, NF1 and RAF1) have been associated the the NS phenotype. Mutations in PTPN11 are the most common. LEOPARD SYNDROME, a disorder that has clinical features overlapping those of Noonan Syndrome, is also due to mutations in PTPN11. In addition, there is overlap with the syndrome called neurofibromatosis-Noonan syndrome due to mutations in NF1.Facial NeoplasmsMosaicism: The occurrence in an individual of two or more cell populations of different chromosomal constitutions, derived from a single ZYGOTE, as opposed to CHIMERISM in which the different cell populations are derived from more than one zygote.Bone Diseases, DevelopmentalChromosomes, Human, Pair 22: A specific pair of GROUP G CHROMOSOMES of the human chromosome classification.Neoplasms, Multiple Primary: Two or more abnormal growths of tissue occurring simultaneously and presumed to be of separate origin. The neoplasms may be histologically the same or different, and may be found in the same or different sites.Piebaldism: Autosomal dominant, congenital disorder characterized by localized hypomelanosis of the skin and hair. The most familiar feature is a white forelock presenting in 80 to 90 percent of the patients. The underlying defect is possibly related to the differentiation and migration of melanoblasts, as well as to defective development of the neural crest (neurocristopathy). Piebaldism may be closely related to WAARDENBURG SYNDROME.Pheochromocytoma: A usually benign, well-encapsulated, lobular, vascular tumor of chromaffin tissue of the ADRENAL MEDULLA or sympathetic paraganglia. The cardinal symptom, reflecting the increased secretion of EPINEPHRINE and NOREPINEPHRINE, is HYPERTENSION, which may be persistent or intermittent. During severe attacks, there may be HEADACHE; SWEATING, palpitation, apprehension, TREMOR; PALLOR or FLUSHING of the face, NAUSEA and VOMITING, pain in the CHEST and ABDOMEN, and paresthesias of the extremities. The incidence of malignancy is as low as 5% but the pathologic distinction between benign and malignant pheochromocytomas is not clear. (Dorland, 27th ed; DeVita Jr et al., Cancer: Principles & Practice of Oncology, 3d ed, p1298)Magnetic Resonance Imaging: Non-invasive method of demonstrating internal anatomy based on the principle that atomic nuclei in a strong magnetic field absorb pulses of radiofrequency energy and emit them as radiowaves which can be reconstructed into computerized images. The concept includes proton spin tomographic techniques.Meningeal Neoplasms: Benign and malignant neoplastic processes that arise from or secondarily involve the meningeal coverings of the brain and spinal cord.Somatostatinoma: A SOMATOSTATIN-secreting tumor derived from the pancreatic delta cells (SOMATOSTATIN-SECRETING CELLS). It is also found in the INTESTINE. Somatostatinomas are associated with DIABETES MELLITUS; CHOLELITHIASIS; STEATORRHEA; and HYPOCHLORHYDRIA. The majority of somatostatinomas have the potential for METASTASIS.Decalcification, Pathologic: The loss of calcium salts from bones and teeth. Bacteria may be responsible for this occurrence in teeth. Old age may be a factor contributing to calcium loss, as is the presence of diseases such as rheumatoid arthritis.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Pigmentation DisordersGlomus Tumor: A blue-red, extremely painful vascular neoplasm involving a glomeriform arteriovenous anastomosis (glomus body), which may be found anywhere in the skin, most often in the distal portion of the fingers and toes, especially beneath the nail. It is composed of specialized pericytes (sometimes termed glomus cells), usually in single encapsulated nodular masses which may be several millimeters in diameter (From Stedman, 27th ed). CHEMODECTOMA, a tumor of NEURAL CREST origin, is also sometimes called a glomus tumor.Optic Chiasm: The X-shaped structure formed by the meeting of the two optic nerves. At the optic chiasm the fibers from the medial part of each retina cross to project to the other side of the brain while the lateral retinal fibers continue on the same side. As a result each half of the brain receives information about the contralateral visual field from both eyes.Adrenal Gland Neoplasms: Tumors or cancer of the ADRENAL GLANDS.Skin Neoplasms: Tumors or cancer of the SKIN.Thoracic NeoplasmsPedigree: The record of descent or ancestry, particularly of a particular condition or trait, indicating individual family members, their relationships, and their status with respect to the trait or condition.Mixed Tumor, Malignant: A malignant tumor composed of more than one type of neoplastic tissue. (Dorland, 27th ed)Astrocytoma: Neoplasms of the brain and spinal cord derived from glial cells which vary from histologically benign forms to highly anaplastic and malignant tumors. Fibrillary astrocytomas are the most common type and may be classified in order of increasing malignancy (grades I through IV). In the first two decades of life, astrocytomas tend to originate in the cerebellar hemispheres; in adults, they most frequently arise in the cerebrum and frequently undergo malignant transformation. (From Devita et al., Cancer: Principles and Practice of Oncology, 5th ed, pp2013-7; Holland et al., Cancer Medicine, 3d ed, p1082)Proteus Syndrome: Hamartoneoplastic malformation syndrome of uncertain etiology characterized by partial GIGANTISM of the hands and/or feet, asymmetry of the limbs, plantar hyperplasia, hemangiomas (HEMANGIOMA), lipomas (LIPOMA), lymphangiomas (LYMPHANGIOMA), epidermal NEVI; MACROCEPHALY; cranial HYPEROSTOSIS, and long-bone overgrowth. Joseph Merrick, the so-called "elephant man", apparently suffered from Proteus syndrome and not NEUROFIBROMATOSIS, a disorder with similar characteristics.Leukemia, Myelomonocytic, Juvenile: A leukemia affecting young children characterized by SPLENOMEGALY, enlarged lymph nodes, rashes, and hemorrhages. Traditionally classed as a myeloproliferative disease, it is now considered a mixed myeloproliferative-mylelodysplastic disorder.Tomography, X-Ray Computed: Tomography using x-ray transmission and a computer algorithm to reconstruct the image.Iris Neoplasms: Tumors of the iris characterized by increased pigmentation of melanocytes. Iris nevi are composed of proliferated melanocytes and are associated with neurofibromatosis and malignant melanoma of the choroid and ciliary body. Malignant melanoma of the iris often originates from preexisting nevi.Angiomatosis: A condition with multiple tumor-like lesions caused either by congenital or developmental malformations of BLOOD VESSELS, or reactive vascular proliferations, such as in bacillary angiomatosis. Angiomatosis is considered non-neoplastic.Arachnoid: A delicate membrane enveloping the brain and spinal cord. It lies between the PIA MATER and the DURA MATER. It is separated from the pia mater by the subarachnoid cavity which is filled with CEREBROSPINAL FLUID.Genetic Linkage: The co-inheritance of two or more non-allelic GENES due to their being located more or less closely on the same CHROMOSOME.