MedGen

Noonan syndrome-14 (NS14) is a recessive developmental disorder within the RASopathy clinical spectrum. Patients exhibit developmental delay, impaired intellectual development, and short stature, as well as distinctive dysmorphic features including bitemporal narrowing, hypertelorism, low-set posteriorly rotated ears, prominent nasal bridge, low posterior hairline with a short webbed neck, and pectus excavatum (Motta et al., 2021). For a general phenotypic description and discussion of genetic heterogeneity of Noonan syndrome, see NS1 (163950). [from OMIM]

Autosomal recessive visceral neuropathy-2 (VSCN2) is characterized by intestinal dysmotility due to aganglionosis or hypoganglionosis of the colon. Patients also exhibit peripheral axonal neuropathy, ptosis, and sensorineural hearing loss (Le et al., 2021). For a discussion of genetic heterogeneity of VSCN, see VSCN1 (243180). [from OMIM]

Familial erythroleukemia is a leukemic or preleukemic state in which red cell proliferation is the predominant feature. Hematologic characteristics include particularly ineffective and hyperplastic erythropoiesis with megaloblastic components accompanied by myeloblastic proliferation of varying degree (Park et al., 2002). Park et al. (2002) discussed the evolution of the definition of 'erythroleukemia,' which is considered by most to be a subtype of acute myelogenous leukemia (AML; 601626). Controversy about the precise definition of erythroleukemia revolves around the number or percentage of erythroblasts and myeloblasts found in the bone marrow and peripheral circulation. In the French-American-British (FAB) classification system (Bennett et al., 1985), it is known as AML-M6, whereas in the revised World Health Organization (WHO) classification system (Harris et al., 1999), it is known as 'AML, not otherwise categorized' (Zini and D'Onofrio, 2004). [from OMIM]

EDFAOB is characterized by linear hypopigmentation and craniofacial asymmetry in association with ocular, dental, and acral anomalies. Brain imaging has revealed some abnormalities, including diffuse cystic leukoencephalopathy and mildly enlarged lateral ventricles, but patients show no intellectual or neurologic impairment (Vabres et al., 2019). [from OMIM]

Capillary malformation-arteriovenous malformation (CM-AVM) syndrome is characterized by the presence of multiple small (1-2 cm in diameter) capillary malformations mostly localized on the face and limbs. Some affected individuals also have associated arteriovenous malformations (AVMs) and/or arteriovenous fistulas (AFVs), fast-flow vascular anomalies that typically arise in the skin, muscle, bone, spine, and brain; life-threatening complications of these lesions can include bleeding, congestive heart failure, and/or neurologic consequences. Symptoms from intracranial AVMs/AVFs appear to occur early in life. Several individuals have Parkes Weber syndrome (multiple micro-AVFs associated with a cutaneous capillary stain and excessive soft-tissue and skeletal growth of an affected limb). [from GeneReviews]

STAT3 hyper IgE syndrome (STAT3-HIES) is a primary immune deficiency syndrome characterized by elevated serum IgE, eczema, and recurrent skin and respiratory tract infections, together with several nonimmune features. This disorder typically manifests in the newborn period with a rash (often diagnosed as eosinophilic pustulosis) that subsequently evolves into an eczematoid dermatitis. Recurrent staphylococcal skin boils and bacterial pneumonias usually manifest in the first years of life. Pneumatoceles and bronchiectasis often result from aberrant healing of pneumonias. Mucocutaneous candidiasis is common. Nonimmune features may include retained primary teeth, scoliosis, bone fractures following minimal trauma, joint hyperextensibility, and characteristic facial appearance, which typically emerges in adolescence. Vascular abnormalities have been described and include middle-sized artery tortuosity and aneurysms, with infrequent clinical sequelae of myocardial infarction and subarachnoid hemorrhage. Gastrointestinal (GI) manifestations include gastroesophageal reflux disease, esophageal dysmotility, and spontaneous intestinal perforations (some of which are associated with diverticuli). Fungal infections of the GI tract (typically histoplasmosis, Cryptococcus, and Coccidioides) also occur infrequently. Survival is typically into adulthood, with most individuals now living into or past the sixth decade. Most deaths are associated with gram-negative (Pseudomonas) or filamentous fungal pneumonias resulting in hemoptysis. Lymphomas occur at an increased frequency. [from GeneReviews]

Schimmelpenning-Feuerstein-Mims syndrome, also known as linear sebaceous nevus syndrome, is characterized by sebaceous nevi, often on the face, associated with variable ipsilateral abnormalities of the central nervous system, ocular anomalies, and skeletal defects (summary by Happle, 1991 and Ernst et al., 2007). The linear sebaceous nevi follow the lines of Blaschko (Hornstein and Knickenberg, 1974; Bouwes Bavinck and van de Kamp, 1985). All cases are sporadic. The syndrome is believed to be caused by an autosomal dominant lethal mutation that survives by somatic mosaicism (Gorlin et al., 2001). [from OMIM]

Amyloidosis cutis dyschromica (ACD), a rare form of primary localized cutaneous amyloidosis, is a pigmentary disorder in which keratinocyte-derived amyloid is deposited in the skin. Onset occurs before puberty and involves macular or reticulate hyperpigmentation admixed with symmetrically distributed guttate hypopigmented and hyperpigmented lesions. ACD can be distinguished from other conditions with similar clinical findings by a skin biopsy in which amyloid deposition in the papillary dermis is seen. Specific features that set ACD apart from the more common macular and lichenoid variants of primary cutaneous amyloidosis include dotted, reticular, or diffuse hyperpigmentation admixed with lentil-sized hypopigmented macules; mild or no associated pruritus; and, on histologic examination of skin from both hyper- and hypopigmented lesions, amyloid deposition confined to the papillary dermis, in close proximity to the epidermis (Huang et al. (2009); Mahon et al., 2016). For a discussion of genetic heterogeneity of primary localized cutaneous amyloidosis, see 105250. [from OMIM]

A rare genetic multiple congenital anomalies/dysmorphic syndrome characterized by global developmental delay and moderate to severe intellectual disability, as well as variable other manifestations, such as macro- or microcephaly, epilepsy, hypotonia, behavioral problems, stereotypic movements, and facial dysmorphism (including arched eyebrows, long palpebral fissures, prominent nasal bridge, upturned nose, dysplastic ears, and broad mouth), among others. Brain imaging may show cerebellar anomalies, hypoplastic corpus callosum, enlarged ventricles, polymicrogyria, or white matter abnormalities. [from ORDO]

Nonmedullary thyroid cancer (NMTC) comprises thyroid cancers of follicular cell origin and accounts for more than 95% of all thyroid cancer cases. The remaining cancers originate from parafollicular cells (medullary thyroid cancer, MTC; 155240). NMTC is classified into 4 groups: papillary, follicular, Hurthle cell (607464), and anaplastic. Approximately 5% of NMTC is hereditary, occurring as a minor component of a familial cancer syndrome (e.g., familial adenomatous polyposis, 175100, Carney complex, 160980) or as a primary feature (familial NMTC or FNMTC). Papillary thyroid cancer (PTC) is the most common histologic subtype of FNMTC, accounting for approximately 85% of cases (summary by Vriens et al., 2009). Follicular thyroid cancer (FTC) accounts for approximately 15% of NMTC and is defined by invasive features that result in infiltration of blood vessels and/or full penetration of the tumor capsule, in the absence of the nuclear alterations that characterize papillary carcinoma. FTC is rarely multifocal and usually does not metastasize to the regional lymph nodes but tends to spread via the bloodstream to the lung and bones. An important histologic variant of FTC is the oncocytic (Hurthle cell, oxyphilic) follicular carcinoma composed of eosinophilic cells replete with mitochondria (summary by Bonora et al., 2010). For a general phenotypic description and a discussion of genetic heterogeneity of NMTC, see NMTC1 (188550). [from OMIM]

Any neonatal inflammatory skin and bowel disease in which the cause of the disease is a mutation in the EGFR gene. [from MONDO]

Infantile-onset multisystem autoimmune disease-1 is characterized by early childhood onset of a spectrum of autoimmune disorders affecting multiple organs. Common manifestations include insulin-dependent diabetes mellitus and autoimmune enteropathy, or celiac disease, and autoimmune hematologic disorders. Other features include short stature and nonspecific dermatitis. More variable features include hypothyroidism, autoimmune arthritis, and delayed puberty. Some patients may show recurrent infections. The disorder results from an inborn error of cytokine signaling (summary by Flanagan et al., 2014 and Milner et al., 2015). Genetic Heterogeneity of Infantile-Onset Multisystem Autoimmune Disease See also ADMIO2 (617006), caused by mutation in the ZAP70 gene (176947) on chromosome 2q12, and ADMIO3 (620430), caused by mutation in the CBLB gene (604491) on chromosome 3q13. [from OMIM]

Pertuzumab is a monoclonal antibody used in the treatment of breast cancer. Pertuzumab was designed to target an epidermal growth factor receptor encoded by the ERBB2 gene, commonly referred to as the HER2 gene. The ERBB2 gene is overexpressed in 15–20% of breast cancers and is also overexpressed in some cases of other cancer types (gastric, colon, head, and neck). Historically, “HER2-positive” tumors are associated with a faster rate of growth and a poorer prognosis than other breast cancer subtypes. The use of pertuzumab in treatment regimens improves outcomes, with limited adverse effects that include cardiac toxicity. Pertuzumab is used with other drugs as an advanced breast cancer treatment, a neoadjuvant treatment, and an adjuvant treatment for HER2-positive breast cancer. In the advanced/metastatic setting, pertuzumab added to trastuzumab and a taxane is used to increase long-term progression-free and overall survival when administered in the first line setting. As neoadjuvant treatment, pertuzumab is given with trastuzumab and chemotherapy before surgery in individuals with early breast cancer to increase pathologic complete response rates. And as an adjuvant treatment, pertuzumab is given with trastuzumab and chemotherapy to reduce the risk of cancer reoccurrence in individuals with early breast cancer. The 2020 FDA-approved drug label states that pertuzumab should only be used to treat individuals with tumors that have either HER2 protein overexpression or ERBB2 gene amplification, as determined by an accurate and validated FDA-approved assay. This is because these are the only individuals studied for whom benefit has been shown. The most recent update (2018) American Society of Clinical Oncology (ASCO) / College of American Pathologists (CAP) guidelines continue to state that all newly diagnosed individuals with breast cancer must have an HER2 test performed. Individuals who then develop metastatic disease must have an HER2 test performed in a metastatic site, if a tissue sample is available. [from Medical Genetics Summaries]

Cardiofaciocutaneous (CFC) syndrome is characterized by cardiac abnormalities (pulmonic stenosis and other valve dysplasias, septal defects, hypertrophic cardiomyopathy, rhythm disturbances), distinctive craniofacial appearance, and cutaneous abnormalities (including xerosis, hyperkeratosis, ichthyosis, keratosis pilaris, ulerythema ophryogenes, eczema, pigmented moles, hemangiomas, and palmoplantar hyperkeratosis). The hair is typically sparse, curly, fine or thick, woolly or brittle; eyelashes and eyebrows may be absent or sparse. Nails may be dystrophic or fast growing. Some form of neurologic and/or cognitive delay (ranging from mild to severe) is seen in all affected individuals. Neoplasia, mostly acute lymphoblastic leukemia, has been reported in some individuals. [from GeneReviews]

Any amyotrophic lateral sclerosis in which the cause of the disease is a mutation in the ERBB4 gene. [from MONDO]

The features of Cowden syndrome overlap with those of another disorder called Bannayan-Riley-Ruvalcaba syndrome. People with Bannayan-Riley-Ruvalcaba syndrome also develop hamartomas and other noncancerous tumors.  Some people with Cowden syndrome have relatives diagnosed with Bannayan-Riley-Ruvalcaba syndrome, and other affected individuals have the characteristic features of both conditions. Based on these similarities, researchers have proposed that Cowden syndrome and Bannayan-Riley-Ruvalcaba syndrome represent a spectrum of overlapping features known as PTEN hamartoma tumor syndrome (named for the genetic cause of the conditions) instead of two distinct conditions.

Some people do not meet the strict criteria for a clinical diagnosis of Cowden syndrome, but they have some of the characteristic features of the condition, particularly the cancers. These individuals are often described as having Cowden-like syndrome. Both Cowden syndrome and Cowden-like syndrome are caused by mutations in the same genes.

Cowden syndrome is associated with an increased risk of developing several types of cancer, particularly cancers of the breast, a gland in the lower neck called the thyroid, and the lining of the uterus (the endometrium). Other cancers that have been identified in people with Cowden syndrome include kidney cancer, colorectal cancer, and an agressive form of skin cancer called melanoma. Compared with the general population, people with Cowden syndrome develop these cancers at younger ages, often beginning in their thirties or forties. People with Cowden syndrome are also more likely to develop more than one cancer during their lifetimes compared to the general population. Other diseases of the breast, thyroid, and endometrium are also common in Cowden syndrome. Additional signs and symptoms can include an enlarged head (macrocephaly) and a rare, noncancerous brain tumor called Lhermitte-Duclos disease. A small percentage of affected individuals have delayed development, intellectual disability, or autism spectrum disorder, which can affect communication and social interaction.

Almost everyone with Cowden syndrome develops hamartomas. These growths are most commonly found on the skin and mucous membranes (such as the lining of the mouth and nose), but they can also occur in the intestine and other parts of the body. The growth of hamartomas on the skin and mucous membranes typically becomes apparent by a person's late twenties.

Cowden syndrome is a genetic disorder characterized by multiple noncancerous, tumor-like growths called hamartomas and an increased risk of developing certain cancers. [from MedlinePlus Genetics]

Noonan syndrome-like disorder is a developmental disorder resembling Noonan syndrome (NS1; 163950) and characterized by facial dysmorphism, a wide spectrum of cardiac disease, reduced growth, variable cognitive deficits, and ectodermal and musculoskeletal anomalies. There is extensive phenotypic heterogeneity and variable expressivity (summary by Martinelli et al., 2010). Patients with heterozygous germline CBL mutations have an increased risk for certain malignancies, particularly juvenile myelomonocytic leukemia (JMML; 607785), as also seen in patients with Noonan syndrome (summary by Niemeyer et al., 2010). [from OMIM]

Trastuzumab is a monoclonal antibody used in the treatment of breast and gastric/gastroesophageal cancer. It targets an epidermal growth factor receptor encoded by the ERBB2 gene, which is commonly referred to as the HER2 gene. Multiple biosimilar products to Herceptin are now available: Kanjinti, Trazimera, Ontruzant, Herzuma and Ogivri. The ERBB2 gene is overexpressed in 15–20% of breast cancers and 15–20% of gastric and esophageal cancers. Overall, “HER2 positive” tumors are associated with a faster rate of growth and—in some cases—a poorer prognosis in absence of anti-HER2 therapy. The use of trastuzumab in treatment regimens improves outcomes, with limited adverse effects that include cardiac toxicity. The FDA-approved drug label states that trastuzumab should only be used to treat individuals with tumors that have either HER2 protein overexpression or ERBB2 gene amplification, as determined by an accurate and validated FDA-approved assay, specific for the type of tumor tested (breast or gastric). The FDA-approved drug label for all trastuzumab biosimilars describes only the use of trastuzumab in adjuvant treatment of breast cancer, though its efficacy in neoadjuvant care for breast cancer and esophageal adenocarcinoma has also been documented. The most recent update (2018) of the American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines continues to state that all newly diagnosed individuals with breast cancer must have an HER2 test performed. Individuals who then develop metastatic disease must have an HER2 test performed in a metastatic site, if tissue sample is available. [from Medical Genetics Summaries]

Panitumumab is a monoclonal antibody used for the treatment of metastatic colorectal cancer (mCRC). Panitumumab is an epidermal growth factor receptor (EGFR) antagonist, which works by blocking the growth of cancer cells. It is administered every 14 days as an intravenous (IV) infusion, often with chemotherapy. Panitumumab is approved for first-line therapy with folinic acid, fluorouracil, and oxaliplatin (FOLFOX) and as monotherapy following disease progression after prior treatment with fluoropyrimidine-, oxaliplatin-, and irinotecan-containing chemotherapy. The location of the primary tumor correlates whether an individual with mCRC is likely respond to anti-EGFR therapy. Individuals with left-sided tumors are more likely to respond well to anti-EGFR therapy and have a better prognosis. Individuals with right-sided tumors have a worse prognosis and respond poorly to anti-EGFR therapy. However, only the genetic variation status of the tumor, and not the location of the tumor, is discussed in the FDA drug label’s dosing recommendations. Resistance to panitumumab is associated with specific RAS mutations. The RAS is a family of oncogenes that includes the KRAS and NRAS genes. When mutated, these genes have the ability to transform normal cells into cancerous cells by providing a continual growth stimulus to cells. The KRAS mutations are particularly common, being detectable in 40% of metastatic colorectal tumors. The KRAS mutations often lead to constitutive activation of the EGFR and are associated with resistance to anti-EGFR drugs such as panitumumab. Mutations in NRAS and another gene, BRAF, have also been associated with poor response to anti-EGFR therapy. The 2017 FDA-approved label states that panitumumab is indicated for wild-type RAS (no mutations in either KRAS or NRAS) mCRC. The label states that an FDA-approved test must be used to confirm the absence of RAS mutations before starting panitumumab, and that panitumumab is not indicated for the treatment of individuals with colorectal cancer with RAS mutations (in either NRAS or KRAS), or when the RAS genetic variation status is unknown. Similarly, the 2015 Update from the American Society of Clinical Oncology (ASCO) states that anti-EGFR therapy should only be considered for the treatment of individuals whose tumor is determined to not have variations detected after extended RAS testing. The 2020 National Comprehensive Cancer Network (NCCN) guideline also strongly recommends KRAS/NRAS genotyping of tumor tissue in all individuals with mCRC. In addition, the guideline states the V600E mutation in the BRAF gene makes a response to panitumumab highly unlikely, unless given with a BRAF inhibitor. [from Medical Genetics Summaries]

Cetuximab is a monoclonal antibody used in the treatment of metastatic colorectal cancer (mCRC) and cancer of the head and neck. Cetuximab is an epidermal growth factor receptor (EGFR) antagonist, which works by blocking the growth of cancer cells. It is administered as a weekly intravenous (IV) infusion, but in practice, is often given every other week to coincide with chemotherapy (for example, FOLFIRI or FOLFOX). Cetuximab has several off-label uses as well, which include non-small cell lung cancer, squamous cell carcinoma of the skin, and Menetrier’s disease. Interestingly, for colorectal cancer, the location of the primary tumor influences whether an individual with mCRC will respond to anti-EGFR therapy, and influences prognosis. Individuals with left-sided tumors are more likely to respond well to anti-EGFR therapy and have a better prognosis. Individuals with right-sided tumors have a worse prognosis and respond poorly to anti-EGFR therapy. However, currently only the mutation status of the tumor, and not the location of the tumor, is discussed in the drug label’s dosing recommendations. Resistance to cetuximab is associated with specific RAS mutations. The RAS family of oncogenes includes the KRAS and NRAS genes. When mutated, these genes have the ability to transform normal cells into cancerous cells. The KRAS mutations are particularly common, being detectable in 40% of metastatic colorectal tumors. The KRAS mutations often lead to constitutive activation of the mitogen-activated protein kinase (MAPK) pathway and are associated with resistance to anti-EGFR drugs such as cetuximab. In addition, mutations in NRAS and another gene, BRAF, have been associated with poor response to anti-EGFR therapy; however, BRAF mutation does not explicitly preclude anti-EGFR therapy. Combination therapies targeting both BRAF and EGFR have shown to improve survival for individuals with wild-type RAS and mutant BRAF. The 2018 FDA-approved drug label for cetuximab states that for mCRC, cetuximab is indicated for K- and N-RAS wild-type (no mutation), EGFR-expressing tumors. The label states that an FDA-approved test must be used to confirm the absence of a RAS mutation (in either KRAS or NRAS) prior to starting cetuximab. While the FDA label also states that EGFR expression should also be confirmed by an approved test prior to starting therapy for mCRC, this is largely not implemented in practice, nor is it recommended by professional oncology society guidelines. Similarly, the 2015 Update from the American Society of Clinical Oncology (ASCO) states that anti-EGFR therapy should only be considered for the treatment of individuals whose tumor is determined to not have mutations detected after extended RAS testing. The 2020 National Comprehensive Cancer Network (NCCN) guideline also strongly recommends KRAS/NRAS genotyping of tumor tissue in all individuals with mCRC. In addition, the guideline states the V600E mutation in the BRAF gene makes a response to cetuximab (and panitumumab) highly unlikely unless given a BRAF inhibitor. [from Medical Genetics Summaries]