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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. [from GeneReviews]

Gastrointestinal stromal tumors are mesenchymal tumors found in the gastrointestinal tract that originate from the interstitial cells of Cajal, the pacemaker cells that regulate peristalsis in the digestive tract. Approximately 70% of GISTs develop in the stomach, 20% in the small intestine, and less than 10% in the esophagus, colon, and rectum. GISTs are typically more cellular than other gastrointestinal sarcomas. They occur predominantly in patients who are 40 to 70 years old but in rare cases may occur in younger persons (Miettinen et al., 1999, 1999). GISTs are also seen as a feature in several syndromes, e.g., neurofibromatosis-1 (NF1; 162200) and GIST-plus syndrome (175510). [from OMIM]

Maturity-onset diabetes of the young (MODY) is a group of several conditions characterized by abnormally high levels of blood glucose, also called blood sugar. These forms of diabetes typically begin before age 30, although they can occur later in life. In MODY, elevated blood glucose arises from reduced production of insulin, which is a hormone produced in the pancreas that helps regulate blood glucose levels. Specifically, insulin controls how much glucose (a type of sugar) is passed from the blood into cells, where it is used as an energy source.

The different types of MODY are distinguished by their genetic causes. The most common types are HNF1A-MODY (also known as MODY3), accounting for 50 to 70 percent of cases, and GCK-MODY (MODY2), accounting for 30 to 50 percent of cases. Less frequent types include HNF4A-MODY (MODY1) and renal cysts and diabetes (RCAD) syndrome (also known as HNF1B-MODY or MODY5), which each account for 5 to 10 percent of cases. At least ten other types have been identified, and these are very rare.

HNF1A-MODY and HNF4A-MODY have similar signs and symptoms that develop slowly over time. Early signs and symptoms in these types are caused by high blood glucose and may include frequent urination (polyuria), excessive thirst (polydipsia), fatigue, blurred vision, weight loss, and recurrent skin infections. Over time uncontrolled high blood glucose can damage small blood vessels in the eyes and kidneys. Damage to the light-sensitive tissue at the back of the eye (the retina) causes a condition known as diabetic retinopathy that can lead to vision loss and eventual blindness. Kidney damage (diabetic nephropathy) can lead to kidney failure and end-stage renal disease (ESRD). While these two types of MODY are very similar, certain features are particular to each type. For example, babies with HNF4A-MODY tend to weigh more than average or have abnormally low blood glucose at birth, even though other signs of the condition do not occur until childhood or young adulthood. People with HNF1A-MODY have a higher-than-average risk of developing noncancerous (benign) liver tumors known as hepatocellular adenomas.

GCK-MODY is a very mild type of the condition. People with this type have slightly elevated blood glucose levels, particularly in the morning before eating (fasting blood glucose). However, affected individuals often have no symptoms related to the disorder, and diabetes-related complications are extremely rare.

RCAD is associated with a combination of diabetes and kidney or urinary tract abnormalities (unrelated to the elevated blood glucose), most commonly fluid-filled sacs (cysts) in the kidneys. However, the signs and symptoms are variable, even within families, and not everyone with RCAD has both features. Affected individuals may have other features unrelated to diabetes, such as abnormalities of the pancreas or liver or a form of arthritis called gout. [from MedlinePlus Genetics]

Chronic lymphocytic leukemia (CLL) is a common neoplasia of B lymphocytes in which these cells progressively accumulate in the bone marrow, blood, and lymphoid tissues. The clinical evolution of the disorder is heterogeneous, with some patients having indolent disease and others having aggressive disease and short survival (summary by Quesada et al., 2012). Genetic Heterogeneity of Susceptibility to Chronic Lymphocytic Leukemia Susceptibility loci have been mapped to chromosomes 11p11 (CLLS1; 609630) and 13q14 (CLLS2; 109543) by genomewide linkage analysis and translocation studies, respectively. Susceptibility mapping to chromosome 9q34 (CLLS3; 612557) is associated with downregulation of the DAPK1 gene (600831). Genomewide association studies have identified susceptibility loci on chromosomes 6p25.3 (CLLS4; 612558) and 11q24.1 (CLLS5; 612559). [from OMIM]

Chylomicron retention disease (CMRD), characterized by the inability to secrete chylomicrons from the enterocytes following the ingestion of fat, typically presents in infancy with failure to thrive, diarrhea, vomiting, abdominal distention, and malabsorption of fat. This leads to steatorrhea – the severity of which relates to the fat content of the diet – and in some cases, hepatomegaly. Organ systems outside of the gastrointestinal tract may also be affected (often due to malnutrition and deficiencies of fat-soluble vitamins), including neuromuscular abnormalities (typically in the first or second decade of life) secondary to vitamin E deficiency, poor bone mineralization and delayed bone maturation due to vitamin D deficiency, prolonged international normalized ratio (INR) due to vitamin K deficiency, mild ophthalmologic issues (e.g., micronystagmus, delayed dark adaptation, abnormal visual evoked potentials, and abnormal scotopic electroretinograms), and (in a small proportion of adults) cardiomyopathy with decreased ejection fraction. Affected individuals typically have marked hypocholesterolemia, low plasma apolipoprotein B levels, normal-to-low plasma triglyceride levels, and low serum concentrations of fat-soluble vitamins (A, D, E, and K). Endoscopy typically demonstrates a gelée blanche ("white hoar frosting") appearance of the duodenal mucosa. [from GeneReviews]

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

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 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.

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.

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.

 [from MedlinePlus Genetics]

TRNT1 deficiency encompasses what was first thought to be two separate disorders, a severe disorder called sideroblastic anemia with B-cell immunodeficiency, periodic fevers, and developmental delay (SIFD) and a milder disorder called retinitis pigmentosa with erythrocytic microcytosis (RPEM), each named for its most common features. SIFD begins in infancy, and affected individuals usually do not survive past childhood. RPEM, on the other hand, is recognized in early adulthood, and the microcytosis usually does not cause any health problems. However, it has since been recognized that some individuals have a combination of features that fall between these two ends of the severity spectrum. All of these cases are now considered part of TRNT1 deficiency.

In addition, many individuals with TRNT1 deficiency have recurrent fevers that are not caused by an infection. These fever episodes are often one of the earliest recognized symptoms of TRNT1 deficiency, usually beginning in infancy. The fever episodes are typically accompanied by poor feeding, vomiting, and diarrhea, and can lead to hospitalization. In many affected individuals, the episodes occur regularly, arising approximately every 2 to 4 weeks and lasting 5 to 7 days, although the frequency can decrease with age.

Many people with TRNT1 deficiency have an immune system disorder (immunodeficiency) that can lead to recurrent bacterial infections. Repeated infections can cause life-threatening damage to internal organs. The immunodeficiency is characterized by low numbers of immune system cells called B cells, which normally help fight infections by producing immune proteins called antibodies (or immunoglobulins). These proteins target foreign invaders such as bacteria and viruses and mark them for destruction. In many individuals with TRNT1 deficiency, the amount of immunoglobulins is also low (hypogammaglobulinemia).

A common feature of TRNT1 deficiency is a blood condition called sideroblastic anemia, which is characterized by a shortage of red blood cells (anemia). In TRNT1 deficiency, the red blood cells that are present are unusually small (erythrocytic microcytosis). In addition, developing red blood cells in the bone marrow (erythroblasts) can have an abnormal buildup of iron that appears as a ring of blue staining in the cell after treatment in the lab with certain dyes. These abnormal cells are called ring sideroblasts.

Neurological problems are also frequent in TRNT1 deficiency. Many affected individuals have delayed development of speech and motor skills, such as sitting, standing, and walking, and some have low muscle tone (hypotonia).

Eye abnormalities, often involving the light-sensing tissue at the back of the eye (the retina), can occur in people with TRNT1 deficiency. Some of these individuals have a condition called retinitis pigmentosa, in which the light-sensing cells of the retina gradually deteriorate. Eye problems in TRNT1 deficiency can lead to vision loss.

Features that occur less commonly in people with TRNT1 deficiency include hearing loss caused by abnormalities of the inner ear (sensorineural hearing loss), recurrent seizures (epilepsy), and problems with the kidneys or heart.

TRNT1 deficiency is a condition that affects many body systems. Its signs and symptoms can involve blood cells, the immune system, the eyes, and the nervous system. The severity of the signs and symptoms vary widely. [from MedlinePlus Genetics]

Agammaglobulinemia is a primary immunodeficiency characterized by profoundly low or absent serum antibodies and low or absent circulating B cells due to an early block of B-cell development. Affected individuals develop severe infections in the first years of life. The most common form of agammaglobulinemia is X-linked agammaglobulinemia (AGMX1, XLA; 300755), also known as Bruton disease, which is caused by mutation in the BTK gene (300300). AGMX1 accounts for anywhere from 85 to 95% of males who have the characteristic findings (Lopez Granados et al., 2002; Ferrari et al., 2007). Autosomal recessive inheritance of agammaglobulinemia, which has a similar phenotype to that of the X-linked form, has been observed in a small number of families, and accounts for up to 15% of patients with agammaglobulinemia (Ferrari et al., 2007). Conley (1999) gave a comprehensive review of autosomal recessive agammaglobulinemia. Genetic Heterogeneity of Autosomal Agammaglobulinemia Autosomal agammaglobulinemia is a genetically heterogeneous disorder: see also AGM2 (613500), caused by mutation in the IGLL1 gene (146770); AGM3 (613501), caused by mutation in the CD79A gene (112205); AGM4 (613502), caused by mutation in the BLNK gene (604515); AGM5 (613506), caused by disruption of the LRRC8 gene (608360); AGM6 (612692), caused by mutation in the CD79B gene (147245); AGM7 (615214), caused by mutation in the PIK3R1 gene (171833); AGM8 (616941), caused by mutation in the TCF3 gene (147141); AGM9 (619693), caused by mutation in the SLC39A7 gene (601416); and AGM10 (619707), caused by mutation in the SPI1 gene (165170). [from OMIM]

A mild form of hemophilia B characterized by a small deficiency of factor IX (biological activity between 5 and 40 IU/dL) leading to abnormal bleeding as a result of minor injuries or following trauma, surgery or tooth extraction. Spontaneous hemorrhages do not occur. The condition may affect males and female carriers of disease-causing mutations. [from ORDO]

Mandibuloacral dysplasia is a condition that causes a variety of abnormalities involving bone development, skin coloring (pigmentation), and fat distribution. People with this condition may grow slowly after birth. Most affected individuals are born with an underdeveloped lower jaw bone (mandible) and small collar bones (clavicles), leading to the characteristic features of a small chin and sloped shoulders. Other bone problems include loss of bone from the tips of the fingers (acroosteolysis), which causes bulbous finger tips; delayed closure of certain skull bones; and joint deformities (contractures).

MADA usually begins in adulthood, although children can be affected. MADB begins earlier, often just after birth. Many babies with MADB are born prematurely.

People with mandibuloacral dysplasia can have mottled or patchy skin pigmentation or other skin abnormalities. Some people with this condition have features of premature aging (a condition called progeria), such as thin skin, loss of teeth, loss of hair, and a beaked nose. Some individuals with mandibuloacral dysplasia have metabolic problems, such as diabetes.

A common feature of mandibuloacral dysplasia is a lack of fatty tissue under the skin (lipodystrophy) in certain regions of the body. The two types of this disorder, mandibuloacral dysplasia with type A lipodystrophy (MADA) and mandibuloacral dysplasia with type B lipodystrophy (MADB) are distinguished by the pattern of fat distribution throughout the body. Type A is described as partial lipodystrophy; affected individuals have a loss of fatty tissue from the torso and limbs, but it may build up around the neck and shoulders. Type B is a generalized lipodystrophy, with loss of fatty tissue in the face, torso, and limbs. [from MedlinePlus Genetics]

Anhidrotic ectodermal dysplasia with immune deficiency (EDA-ID) is a form of ectodermal dysplasia, which is a group of conditions characterized by abnormal development of ectodermal tissues including the skin, hair, teeth, and sweat glands. In addition, immune system function is reduced in people with EDA-ID. The signs and symptoms of EDA-ID are evident soon after birth, and due to the severity of the immune system problems, most people with this condition survive only into childhood.

Skin abnormalities in children with EDA-ID include areas that are dry, wrinkled, or darker in color than the surrounding skin. Affected individuals tend to have sparse scalp and body hair (hypotrichosis). EDA-ID is also characterized by missing teeth (hypodontia) or teeth that are small and pointed. Most children with EDA-ID have a reduced ability to sweat (hypohidrosis) because they have fewer sweat glands than normal or their sweat glands do not function properly. An inability to sweat (anhidrosis) can lead to a dangerously high body temperature (hyperthermia), particularly in hot weather and during exercise, because the body cannot cool itself by evaporating sweat.

The immune deficiency in EDA-ID varies among individuals with this condition. Children with EDA-ID often produce abnormally low levels of proteins called antibodies or immunoglobulins. Antibodies help protect the body against infection by attaching to specific foreign particles and germs, marking them for destruction. A reduction in antibodies makes it difficult for children with this disorder to fight off infections. In EDA-ID, immune system cells called T cells and B cells have a decreased ability to recognize and respond to foreign invaders (such as bacteria, viruses, and yeast) that have sugar molecules attached to their surface (glycan antigens). Other key aspects of the immune system may also be impaired, leading to recurrent infections.

Children with EDA-ID commonly get infections in the lungs (pneumonia), ears (otitis media), sinuses (sinusitis), lymph nodes (lymphadenitis), skin, bones, and gastrointestinal tract. Approximately one quarter of individuals with EDA-ID have disorders involving abnormal inflammation, such as inflammatory bowel disease or rheumatoid arthritis.

There are two forms of EDA-ID that have similar signs and symptoms and are distinguished by the modes of inheritance: X-linked recessive or autosomal dominant. [from MedlinePlus Genetics]

A neoplasm of lymphoblasts committed to the B-cell lineage, typically composed of small to medium-sized blast cells. When the neoplasm involves predominantly the bone marrow and the peripheral blood, it is called B acute lymphoblastic leukemia. When it involves nodal or extranodal sites, it is called B lymphoblastic lymphoma. (WHO, 2001) [from NCI]

The atherogenic lipoprotein phenotype (ALP) is a common heritable trait characterized by a preponderance of small, dense low density lipoprotein (LDL) particles (subclass pattern B), increased levels of triglyceride-rich lipoproteins, reduction in high density lipoprotein, and a 3-fold increased risk of myocardial infarction (summary by Nishina et al., 1992). The so-called atherogenic lipoprotein phenotype was shown by Austin et al. (1988) to be independently associated with an increased risk for coronary artery disease. Allayee et al. (1998) concluded, furthermore, that there is a genetically based association between familial combined hyperlipidemia (FCHL; 144250) and small, dense LDL particles and that the genetic determinants for LDL particle size are shared, at least in part, among FCHL families and the more general population at risk for coronary artery disease. Juo et al. (1998) concluded from a bivariate segregation analysis of small, dense LDL particles and elevated apolipoprotein B levels (APOB; 107730), which are commonly found together in members of FCHL families, that the 2 traits share a common major gene plus individual polygenic components. The common major gene was estimated to explain 37% of the variance of adjusted LDL particle size and 23% of the variance of adjusted apoB levels. [from OMIM]

A rare B-cell non-Hodgkin lymphoma characterised by the presence of small B-lymphocytes, plasmacytoid lymphocytes and plasma cells, and either non-secreting or secreting IgG or IgA paraproteins. The disease usually involves the bone marrow and sometimes also the spleen or lymph nodes. Patients typically present with symptoms related to anaemia. Hyperviscosity, autoimmune phenomena and B symptoms may also be observed. Mortality is higher as compared to Waldenström macroglobulinaemia. [from SNOMEDCT_US]

A rare, indolent primary cutaneous B-cell lymphoma characterized by multifocal, red to violaceous papules, plaques or nodules localized predominantly on the trunk and extremities. Histologically, these are dermis infiltrates consisting of small, marginal zone B cells, lymphoplasmacytic cells, and plasma cells. Marginal zone B cells express CD20, CD79a and Bcl-2, and are negative for CD5, CD10 and Bcl-6. Plasma cells are typically located at the periphery, and express CD138, CD79a, and monotypic light chains. [from ORDO]

The most common type of non-Hodgkin lymphoma. It includes the most frequently seen morphologic variants which are: diffuse large B-cell lymphoma, follicular lymphoma, small lymphocytic lymphoma and marginal zone B-cell lymphoma. -- 2003 [from MONDO]

A lymphoproliferative abnormality of the intestine characterized by numerous visible mucosal nodules measuring up to, and rarely exceeding, 0.5 cm in diameter Histologically, hyperplastic lymphoid follicles with large germinal centers are seen in the lamina propria and superficial submucosa. There is enlargement of the mucosal B cell follicles caused by hyperplasia of the follicle centers; surrounded by a normal appearing mantle zone. Disease may involve the stomach, the entire small intestine, and the large intestine. [from HPO]

Immunodeficiency-100 with pulmonary alveolar proteinosis and hypogammaglobulinemia (IMD100) is primarily a lung disorder characterized by onset of respiratory insufficiency due to pulmonary alveolar proteinosis (PAP) in the first months of life. Affected individuals may have normal respiratory function at birth. Development of the disorder appears to be influenced or triggered by viral infection, manifest as progressive respiratory insufficiency, confluent consolidations on lung imaging, and diffuse collection of periodic acid-Schiff (PAS)-positive material in pulmonary alveoli associated with small and nonfoamy alveolar macrophages. Patients also have hypogammaglobulinemia, leukocytosis, and splenomegaly. Many patients die of respiratory failure in infancy or early childhood; hematopoietic stem cell transplantation (HSCT) is curative. The pathogenesis may be related to abnormal function of alveolar macrophages, resulting in decreased catabolism of surfactant (summary by Cho et al., 2018). Magg et al. (2021) determined that the disorder results from a gain-of-function effect that particularly affects B cells and monocytes. [from OMIM]

Microvillus inclusion disease (DIAR12) is a congenital enteropathy characterized by neonatal-onset intractable secretory diarrhea, resulting in severe dehydration and metabolic acidosis. Patients may tolerate limited enteral feeding, but are dependent on total parenteral nutrition (TPN) and require eventual small bowel and/or liver transplantation. Pathologic hallmarks include variable loss of brush-border microvilli, microvillus inclusions, and accumulation of subapical vesicles in villus enterocytes (summary by Wiegerinck et al., 2014). Another form of microvillus inclusion disease, MVID1 (DIAR2; 251850), is caused by mutation in the MYO5B gene (606540). For a discussion of genetic heterogeneity of diarrhea, see DIAR1 (214700). Mutations in the STX3 gene that affect only isoform A (STX3A) cause DIAR12, whereas mutations in STX3 affecting both STX3A and isoform B (STX3B), which predominates in retinal tissue, cause a syndrome involving severe early-onset retinal dystrophy and MVID (RDMVID; 619446). [from OMIM]

Mantle cell lymphoma is a rare form of malignant non-Hodgkin lymphoma (see this term) affecting B lymphocytes in the lymph nodes in a region called the ``mantle zone''. [from ORDO]