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.

Lynch syndrome-5 (LYNCH5), or hereditary nonpolyposis colorectal cancer type 5 (HNPCC5), is a cancer predisposition syndrome characterized by onset of colorectal cancer and/or extracolonic cancers, particularly endometrial cancer, usually in mid-adulthood. The disorder shows autosomal dominant inheritance with incomplete penetrance (summary by Castellsague et al., 2015). For a general phenotypic description and a discussion of genetic heterogeneity of Lynch syndrome, see 120435.

Lynch syndrome-4 (LYNCH4), or hereditary nonpolyposis colorectal cancer type 4 (HNPCC4), is an autosomal dominant disorder characterized primarily by the development of early-onset colorectal cancer. It is associated with the development of a variety of epithelial tumors that include endometrial cancer, stomach cancer, and ovarian cancer (summary by Thompson et al., 2004).

BRCA1- and BRCA2-associated hereditary breast and ovarian cancer (HBOC) is characterized by an increased risk for female and male breast cancer, ovarian cancer (including fallopian tube and primary peritoneal cancers), and to a lesser extent other cancers such as prostate cancer, pancreatic cancer, and melanoma primarily in individuals with a BRCA2 pathogenic variant. The risk of developing an associated cancer varies depending on whether HBOC is caused by a BRCA1 or BRCA2 pathogenic variant.

BRCA1- and BRCA2-associated hereditary breast and ovarian cancer (HBOC) is characterized by an increased risk for female and male breast cancer, ovarian cancer (including fallopian tube and primary peritoneal cancers), and to a lesser extent other cancers such as prostate cancer, pancreatic cancer, and melanoma primarily in individuals with a BRCA2 pathogenic variant. The risk of developing an associated cancer varies depending on whether HBOC is caused by a BRCA1 or BRCA2 pathogenic variant.

Premature ovarian failure (POF), the endpoint of primary ovarian insufficiency, affects approximately 1% of women worldwide. Patients with POF present with at least a 6-month history of amenorrhea and elevated plasma levels of follicle-stimulating hormone (more than 40 mIU per milliliter). The disorder can result from premature depletion of the follicle pool, follicular atresia, follicle growth arrest, or ovarian dysgenesis (see 233300). In approximately 10 to 15% of patients with POF, a genetic cause has been determined (summary by Caburet et al., 2014). For general phenotypic information and a discussion of genetic heterogeneity of premature ovarian failure, see POF1 (311360).

Nonmedullary thyroid cancer (NMTC) refers to neoplasms originating from the thyroid follicular cells and represents 80 to 95% of all thyroid cancers. Approximately 5% of NMTC occurs on the background of a familial predisposition. Although papillary thyroid carcinoma (PTC) is usually the most frequent thyroid lesion in NMTC families, multinodular goiter (MNG) and follicular thyroid adenoma also occur (summary by Pereira et al., 2015). For a general phenotypic description and a discussion of genetic heterogeneity of NMTC, see NMTC1 (188550).

Fanconi anemia (FA) is characterized by physical abnormalities, bone marrow failure, and increased risk for malignancy. Physical abnormalities, present in approximately 75% of affected individuals, include one or more of the following: short stature, abnormal skin pigmentation, skeletal malformations of the upper and/or lower limbs, microcephaly, and ophthalmic and genitourinary tract anomalies. Progressive bone marrow failure with pancytopenia typically presents in the first decade, often initially with thrombocytopenia or leukopenia. The incidence of acute myeloid leukemia is 13% by age 50 years. Solid tumors – particularly of the head and neck, skin, and genitourinary tract – are more common in individuals with FA.