Neurofibromatosis 1 (NF1) is a multisystem disorder characterized by multiple café au lait macules, intertriginous freckling, multiple cutaneous neurofibromas, and learning disability or behavior problems. About half of people with NF1 have plexiform neurofibromas, but most are internal and not suspected clinically. Plexiform neurofibromas can cause pain, neurologic deficits, and abnormalities of involved or adjacent structures. Less common but potentially more serious manifestations include optic nerve and other central nervous system gliomas, malignant peripheral nerve sheath tumors, scoliosis, tibial dysplasia, vasculopathy, and gastrointestinal, endocrine, or pulmonary disease.

Neurofibromatosis 2 (NF2) is characterized by bilateral vestibular schwannomas with associated symptoms of tinnitus, hearing loss, and balance dysfunction. The average age of onset is 18 to 24 years. Almost all affected individuals develop bilateral vestibular schwannomas by age 30 years. Affected individuals may also develop schwannomas of other cranial and peripheral nerves, meningiomas, ependymomas, and, very rarely, astrocytomas. Because NF2 is considered an adult-onset disease, it may be underrecognized in children, in whom skin tumors and ocular findings (retinal hamartoma, thickened optic nerves, cortical wedge cataracts, third cranial nerve palsy) may be the first manifestations. Mononeuropathy that occurs in childhood is an increasingly recognized finding; it frequently presents as a persistent facial palsy or hand/foot drop.

Encephalocraniocutaneous lipomatosis (ECCL) comprises a spectrum of predominantly congenital anomalies. In its typical form, ECCL is characterized by congenital anomalies of the skin (nevus psiloliparus, patchy or streaky non-scarring alopecia, subcutaneous lipomas in the frontotemporal region, focal skin aplasia or hypoplasia on the scalp, and/or small nodular skin tags on the eyelids or between the outer canthus and tragus), eye (choristoma), and brain (in particular intracranial and spinal lipomas). To a much lesser degree, the bones and the heart can be affected. About 40% of affected individuals have bilateral abnormalities of the skin or the eyes. About one third of affected individuals have normal cognitive development, another one third have mild developmental delay (DD) or intellectual disability (ID), and the final one third have severe or unspecified DD/ID. Half of individuals have seizures. Affected individuals are at an increased (i.e., above the general population) risk of developing brain tumors, particularly low-grade gliomas such as pilocytic astrocytomas. There is evidence that oculoectodermal syndrome (OES) may constitute a clinical spectrum with ECCL, with OES on the mild end and ECCL on the more severe end of the spectrum.

An extremely rare tumor association characterized by dual predisposition to melanoma and neural system tumors (typically astrocytoma). Fewer than 20 affected families have been reported to date. Affected individuals had cutaneous melanoma in association with dysplastic nevi, astrocytoma, benign or malignant peripheral nerve sheath tumor, neurofibroma, medulloblastoma, glioblastoma multiforme, ependymoma, glioma, and meningioma. In some cases, melanoma was described first followed by nervous system tumors, and in other cases, melanoma was a secondary cancer. The etiology of this tumor association is unknown. Genetic mutations or germline deletions are thought to underlie this cancer susceptibility syndrome.

Tuberous sclerosis complex (TSC) involves abnormalities of the skin (hypomelanotic macules, confetti skin lesions, facial angiofibromas, shagreen patches, fibrous cephalic plaques, ungual fibromas); brain (subependymal nodules, cortical tubers, and subependymal giant cell astrocytomas [SEGAs], seizures, intellectual disability / developmental delay, psychiatric illness); kidney (angiomyolipomas, cysts, renal cell carcinomas); heart (rhabdomyomas, arrhythmias); and lungs (lymphangioleiomyomatosis [LAM], multifocal micronodular pneumonocyte hyperplasia). Central nervous system tumors are the leading cause of morbidity and mortality; renal disease is the second leading cause of early death.

Tuberous sclerosis complex (TSC) involves abnormalities of the skin (hypomelanotic macules, confetti skin lesions, facial angiofibromas, shagreen patches, fibrous cephalic plaques, ungual fibromas); brain (subependymal nodules, cortical tubers, and subependymal giant cell astrocytomas [SEGAs], seizures, intellectual disability / developmental delay, psychiatric illness); kidney (angiomyolipomas, cysts, renal cell carcinomas); heart (rhabdomyomas, arrhythmias); and lungs (lymphangioleiomyomatosis [LAM], multifocal micronodular pneumonocyte hyperplasia). Central nervous system tumors are the leading cause of morbidity and mortality; renal disease is the second leading cause of early death.

APC-associated polyposis conditions include (classic or attenuated) familial adenomatous polyposis (FAP) and gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS). FAP is a colorectal cancer (CRC) predisposition syndrome that can manifest in either classic or attenuated form. Classic FAP is characterized by hundreds to thousands of adenomatous colonic polyps, beginning on average at age 16 years (range 7-36 years). For those with the classic form of FAP, 95% of individuals have polyps by age 35 years; CRC is inevitable without colectomy. The mean age of CRC diagnosis in untreated individuals is 39 years (range 34-43 years). The attenuated form is characterized by multiple colonic polyps (average of 30), more proximally located polyps, and a diagnosis of CRC at a later age than in classic FAP. For those with an attenuated form, there is a 70% lifetime risk of CRC and the mean age of diagnosis is 50-55 years. Extracolonic manifestations are variably present and include polyps of the stomach and duodenum, osteomas, dental abnormalities, congenital hypertrophy of the retinal pigment epithelium (CHRPE), benign cutaneous lesions, desmoid tumors, adrenal masses, and other associated cancers. GAPPS is characterized by proximal gastric polyposis, increased risk of gastric adenocarcinoma, and no duodenal or colonic involvement in most individuals reported.

Gliomas are central nervous system neoplasms derived from glial cells and comprise astrocytomas, glioblastoma multiforme, oligodendrogliomas, ependymomas, and subependymomas. Glial cells can show various degrees of differentiation even within the same tumor (summary by Kyritsis et al., 2010). Ependymomas are rare glial tumors of the brain and spinal cord (Yokota et al., 2003). Subependymomas are unusual tumors believed to arise from the bipotential subependymal cell, which normally differentiates into either ependymal cells or astrocytes. They were characterized as a distinct entity by Scheinker (1945). They tend to be slow-growing, noninvasive, and located in the ventricular system, septum pellucidum, cerebral aqueduct, or proximal spinal cord (summary by Ryken et al., 1994). Gliomas are known to occur in association with several other well-defined hereditary tumor syndromes such as mismatch repair cancer syndrome (see 276300), melanoma-astrocytoma syndrome (155755), neurofibromatosis-1 (NF1; 162200) and neurofibromatosis-2 (see SWNV, 101000), and tuberous sclerosis (TSC1; 191100). Familial clustering of gliomas may occur in the absence of these tumor syndromes, however. Genetic Heterogeneity of Susceptibility to Glioma Other glioma susceptibilities include GLM2 (613028), caused by variation in the PTEN gene (601728) on chromosome 10q23; GLM3 (613029), caused by variation in the BRCA2 gene (600185) on chromosome 13q13; GLM4 (607248), mapped to chromosome 15q23-q26.3; GLM5 (613030), mapped to chromosome 9p21; GLM6 (613031), mapped to chromosome 20q13; GLM7 (613032), mapped to chromosome 8q24; GLM8 (613033), mapped to chromosome 5p15; and GLM9, caused by variation in the POT1 gene (606478) on chromosome 7q31. Somatic mutation, disruption, or copy number variation of the following genes or loci may also contribute to the formation of glioma: ERBB (EGFR; 131550), ERBB2 (164870), LGI1 (604619), GAS41 (602116), GLI (165220), DMBT1 (601969), IDH1 (147700), IDH2 (147650), BRAF (164757), PARK2 (602544), TP53 (191170), RB1 (614041), PIK3CA (171834), 10p15, 19q, and 17p13.3.

Any malignant glioma in which the cause of the disease is a mutation in the BRCA2 gene.

Familial adenomatous polyposis-4 is an autosomal recessive tumor predisposition syndrome characterized by the development of multiple colonic adenomas in adulthood, often with progression to colorectal cancer. Proliferative lesions in other tissues may also occur (summary by Adam et al., 2016). For a discussion of genetic heterogeneity of familial adenomatous polyposis, see FAP1 (175100).

Lynch syndrome is characterized by an increased risk for colorectal cancer (CRC) and cancers of the endometrium, ovary, stomach, small bowel, urinary tract, biliary tract, brain (usually glioblastoma), skin (sebaceous adenomas, sebaceous carcinomas, and keratoacanthomas), pancreas, and prostate. Cancer risks and age of onset vary depending on the associated gene. Several other cancer types have been reported to occur in individuals with Lynch syndrome (e.g., breast, sarcomas, adrenocortical carcinoma). However, the data are not sufficient to demonstrate that the risk of developing these cancers is increased in individuals with Lynch syndrome.

Mismatch repair cancer syndrome-3 (MMRCS3) is an autosomal recessive childhood cancer predisposition syndrome characterized by brain tumors, hematologic malignancy, and gastrointestinal tumors. Multiple cafe-au-lait spots, axillary freckling, and, rarely, Lisch nodules reminiscent of neurofibromatosis type I (NF1; 162200) may be present (Hegde et al., 2005, Ostergaard et al., 2005). Microsatellite instability may be detected in tumor samples (Hegde et al., 2005). For a discussion of genetic heterogeneity of mismatch repair cancer syndrome, see MMRCS1 (276300).

Mismatch repair cancer syndrome-4 (MMRCS4) is an autosomal recessive childhood cancer predisposition syndrome characterized by early-onset leukemia/lymphoma, brain tumors, colorectal/gastrointestinal cancers, and other rare malignancies, including rhabdomyosarcoma (summary by Li et al., 2015). Cafe-au-lait spots are usually present (De Vos et al., 2006). For a discussion of genetic heterogeneity of mismatch repair cancer syndrome, see MMRCS1 (276300).