bowang0911/MedQuAD huggingface dataset:
An epidermal nevus (plural: nevi) is an abnormal, noncancerous (benign) patch of skin caused by an overgrowth of skin cells. Epidermal nevi are typically seen at birth or develop in early childhood. They can be flat, tan patches of skin or raised, velvety patches. As the affected individual ages, the nevus can become thicker and darker and develop a wart-like (verrucous) appearance. Often, epidermal nevi follow a pattern on the skin known as the lines of Blaschko. The lines of Blaschko, which are invisible on skin, are thought to follow the paths along which cells migrate as the skin develops before birth.  There are several types of epidermal nevi that are defined in part by the type of skin cell involved. The epidermis is the outermost layer of skin and is composed primarily of a specific cell type called a keratinocyte. One group of epidermal nevi, called keratinocytic or nonorganoid epidermal nevi, includes nevi that involve only keratinocytes. Other types of epidermal nevi involve additional types of epidermal cells, such as the cells that make up the hair follicles or the sebaceous glands (glands in the skin that produce a substance that protects the skin and hair). These nevi comprise a group called organoid epidermal nevi.  Some affected individuals have only an epidermal nevus and no other abnormalities. However, sometimes people with an epidermal nevus also have problems in other body systems, such as the brain, eyes, or bones. In these cases, the affected individual has a condition called an epidermal nevus syndrome. There are several different epidermal nevus syndromes characterized by the type of epidermal nevus involved.
Mutations in the FGFR3 gene have been found in approximately 30 percent of people with a type of nevus in the keratinocytic epidermal nevi group. The gene mutations involved in most epidermal nevi are unknown.  Mutations associated with an epidermal nevus are present only in the cells of the nevus, not in the normal skin cells surrounding it. Because the mutation is found in some of the body's cells but not in others, people with an epidermal nevus are said to be mosaic for the mutation.  The FGFR3 gene provides instructions for the fibroblast growth factor receptor 3 (FGFR3) protein. This protein is involved in several important cellular processes, including regulation of growth and division of skin cells. The FGFR3 protein interacts with specific growth factors outside the cell to receive signals that control growth and development. When these growth factors attach to the FGFR3 protein, the protein is turned on (activated), which triggers a cascade of chemical reactions inside the cell that control growth and other cellular functions.  The most common FGFR3 gene mutation in epidermal nevi creates a protein that is turned on without attachment of a growth factor, which means that the FGFR3 protein is constantly active. Cells with a mutated FGFR3 gene grow and divide more than normal cells. In addition, these mutated cells do not undergo a form of self-destruction called apoptosis as readily as normal cells. These effects result in overgrowth of skin cells, leading to epidermal nevi.
Trisomy 18, also called Edwards syndrome, is a chromosomal condition associated with abnormalities in many parts of the body. Individuals with trisomy 18 often have slow growth before birth (intrauterine growth retardation) and a low birth weight. Affected individuals may have heart defects and abnormalities of other organs that develop before birth. Other features of trisomy 18 include a small, abnormally shaped head; a small jaw and mouth; and clenched fists with overlapping fingers. Due to the presence of several life-threatening medical problems, many individuals with trisomy 18 die before birth or within their first month. Five to 10 percent of children with this condition live past their first year, and these children often have severe intellectual disability.
Most cases of trisomy 18 result from having three copies of chromosome 18 in each cell in the body instead of the usual two copies. The extra genetic material disrupts the normal course of development, causing the characteristic features of trisomy 18.  Approximately 5 percent of people with trisomy 18 have an extra copy of chromosome 18 in only some of the body's cells. In these people, the condition is called mosaic trisomy 18. The severity of mosaic trisomy 18 depends on the type and number of cells that have the extra chromosome. The development of individuals with this form of trisomy 18 may range from normal to severely affected.  Very rarely, part of the long (q) arm of chromosome 18 becomes attached (translocated) to another chromosome during the formation of reproductive cells (eggs and sperm) or very early in embryonic development. Affected individuals have two copies of chromosome 18, plus the extra material from chromosome 18 attached to another chromosome. People with this genetic change are said to have partial trisomy 18. If only part of the q arm is present in three copies, the physical signs of partial trisomy 18 may be less severe than those typically seen in trisomy 18. If the entire q arm is present in three copies, individuals may be as severely affected as if they had three full copies of chromosome 18.
Most cases of trisomy 18 are not inherited, but occur as random events during the formation of eggs and sperm. An error in cell division called nondisjunction results in a reproductive cell with an abnormal number of chromosomes. For example, an egg or sperm cell may gain an extra copy of chromosome 18. If one of these atypical reproductive cells contributes to the genetic makeup of a child, the child will have an extra chromosome 18 in each of the body's cells.  Mosaic trisomy 18 is also not inherited. It occurs as a random event during cell division early in embryonic development. As a result, some of the body's cells have the usual two copies of chromosome 18, and other cells have three copies of this chromosome.  Partial trisomy 18 can be inherited. An unaffected person can carry a rearrangement of genetic material between chromosome 18 and another chromosome. This rearrangement is called a balanced translocation because there is no extra material from chromosome 18. Although they do not have signs of trisomy 18, people who carry this type of balanced translocation are at an increased risk of having children with the condition.
Langer-Giedion syndrome is a condition that causes bone abnormalities and distinctive facial features. People with this condition have multiple noncancerous (benign) bone tumors called osteochondromas. Multiple osteochondromas may result in pain, limited range of joint movement, and pressure on nerves, blood vessels, the spinal cord, and tissues surrounding the osteochondromas. Affected individuals also have short stature and cone-shaped ends of the long bones (epiphyses). The characteristic appearance of individuals with Langer-Giedion syndrome includes sparse scalp hair, a rounded nose, a long flat area between the nose and the upper lip (philtrum), and a thin upper lip. Some people with this condition have loose skin in childhood, which typically resolves with age. Affected individuals may have some intellectual disability.
Langer-Giedion syndrome is caused by the deletion or mutation of at least two genes on chromosome 8. Researchers have determined that the loss of a functional EXT1 gene is responsible for the multiple osteochondromas seen in people with Langer-Giedion syndrome. Loss of a functional TRPS1 gene may cause the other bone and facial abnormalities. The EXT1 gene and the TRPS1 gene are always missing or mutated in affected individuals, but other neighboring genes may also be involved. The loss of additional genes from this region of chromosome 8 likely contributes to the varied features of this condition.  Langer-Giedion syndrome is often described as a contiguous gene deletion syndrome because it results from the loss of several neighboring genes.
Most cases of Langer-Giedion syndrome are not inherited, but occur as random events during the formation of reproductive cells (eggs or sperm) in a parent of an affected individual. These cases occur in people with no history of the disorder in their family. There have been very few instances in which people with Langer-Giedion syndrome have inherited the chromosomal deletion from a parent with the condition.  Langer-Giedion syndrome is considered an autosomal dominant condition because one copy of the altered chromosome 8 in each cell is sufficient to cause the disorder.
Leigh syndrome is a severe neurological disorder that typically arises in the first year of life. This condition is characterized by progressive loss of mental and movement abilities (psychomotor regression) and typically results in death within a couple of years, usually due to respiratory failure. A small number of individuals develop symptoms in adulthood or have symptoms that worsen more slowly.  The first signs of Leigh syndrome seen in infancy are usually vomiting, diarrhea, and difficulty swallowing (dysphagia) that leads to eating problems. These problems often result in an inability to grow and gain weight at the expected rate (failure to thrive). Severe muscle and movement problems are common in Leigh syndrome. Affected individuals may develop weak muscle tone (hypotonia), involuntary muscle contractions (dystonia), and problems with movement and balance (ataxia). Loss of sensation and weakness in the limbs (peripheral neuropathy), common in people with Leigh syndrome, may also make movement difficult.  Several other features may occur in people with Leigh syndrome. Many affected individuals develop weakness or paralysis of the muscles that move the eyes (ophthalmoparesis); rapid, involuntary eye movements (nystagmus); or degeneration of the nerves that carry information from the eyes to the brain (optic atrophy). Severe breathing problems are common in people with Leigh syndrome, and these problems can worsen until they cause acute respiratory failure. Some affected individuals develop hypertrophic cardiomyopathy, which is a thickening of the heart muscle that forces the heart to work harder to pump blood. In addition, a substance called lactate can build up in the body, and excessive amounts are often found in the blood, cerebrospinal fluid, or urine of people with Leigh syndrome.  The signs and symptoms of Leigh syndrome are caused in part by patches of damaged tissue (lesions) that develop in the brains of people with this condition. A procedure called magnetic resonance imaging (MRI) reveals characteristic lesions in certain regions of the brain and the brainstem (the part of the brain that is connected to the spinal cord). These regions include the basal ganglia, which help control movement; the cerebellum, which controls the ability to balance and coordinates movement; and the brainstem, which controls functions such as swallowing, breathing, hearing, and seeing. The brain lesions are often accompanied by loss of the myelin coating around nerves (demyelination), which reduces the ability of the nerves to activate muscles used for movement or relay sensory information back to the brain.
Leigh syndrome can have different inheritance patterns. It is most commonly inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. This pattern of inheritance applies to genes contained in nuclear DNA. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.  In about 20 to 25 percent of people with Leigh syndrome, the condition is inherited in a mitochondrial pattern, which is also known as maternal inheritance. This pattern of inheritance applies to genes contained in mtDNA. Because egg cells, but not sperm cells, contribute mitochondria to the developing embryo, children can only inherit disorders resulting from mtDNA mutations from their mother. These disorders can appear in every generation of a family and can affect both males and females, but fathers do not pass traits associated with changes in mtDNA to their children. Occasionally, mutations in mtDNA occur spontaneously, and there is no history of Leigh syndrome in the family.  In a small number of affected individuals with mutations in nuclear DNA, Leigh syndrome is inherited in an X-linked recessive pattern. The condition has this pattern of inheritance when the mutated gene is located on the X chromosome, which is one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In females (who have two X chromosomes), a mutation would have to occur in both copies of the gene to cause the disorder. Because it is unlikely that females will have two altered copies of this gene, males are affected by X-linked recessive disorders much more frequently than females. A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.
These resources address the diagnosis or management of Leigh syndrome:  - Gene Review: Gene Review: Mitochondrial DNA-Associated Leigh Syndrome and NARP  - Gene Review: Gene Review: Nuclear Gene-Encoded Leigh Syndrome Overview  - Genetic Testing Registry: Leigh Syndrome (mtDNA mutation)  - Genetic Testing Registry: Leigh Syndrome (nuclear DNA mutation)  - Genetic Testing Registry: Leigh syndrome  - Genetic Testing Registry: Leigh syndrome, French Canadian type   These resources from MedlinePlus offer information about the diagnosis and management of various health conditions:  - Diagnostic Tests  - Drug Therapy  - Surgery and Rehabilitation  - Genetic Counseling   - Palliative Care
Heterotaxy syndrome is a condition in which the internal organs are abnormally arranged in the chest and abdomen. The term "heterotaxy" is from the Greek words "heteros," meaning "other than," and "taxis," meaning "arrangement." Individuals with this condition have complex birth defects affecting the heart, lungs, liver, spleen, intestines, and other organs.  In the normal body, most of the organs in the chest and abdomen have a particular location on the right or left side. For example, the heart, spleen, and pancreas are on the left side of the body, and most of the liver is on the right. This normal arrangement of the organs is known as "situs solitus." Rarely, the orientation of the internal organs is completely flipped from right to left, a situation known as "situs inversus." This mirror-image orientation usually does not cause any health problems, unless it occurs as part of a syndrome affecting other parts of the body. Heterotaxy syndrome is an arrangement of internal organs somewhere between situs solitus and situs inversus; this condition is also known as "situs ambiguus." Unlike situs inversus, the abnormal arrangement of organs in heterotaxy syndrome often causes serious health problems.  Heterotaxy syndrome alters the structure of the heart, including the attachment of the large blood vessels that carry blood to and from the rest of the body. It can also affect the structure of the lungs, such as the number of lobes in each lung and the length of the tubes (called bronchi) that lead from the windpipe to the lungs. In the abdomen, the condition can cause a person to have no spleen (asplenia) or multiple small, poorly functioning spleens (polysplenia). The liver may lie across the middle of the body instead of being in its normal position to the right of the stomach. Some affected individuals also have intestinal malrotation, which is an abnormal twisting of the intestines that occurs in the early stages of development before birth.  Depending on the organs involved, signs and symptoms of heterotaxy syndrome can include a bluish appearance of the skin or lips (cyanosis, which is due to a shortage of oxygen), breathing difficulties, an increased risk of infections, and problems with digesting food. The most serious complications are generally caused by critical congenital heart disease, a group of complex heart defects that are present from birth. Biliary atresia, a problem with the bile ducts in the liver, can also cause severe health problems in infancy. Heterotaxy syndrome is often life-threatening in infancy or childhood, even with treatment, although its severity depends on the specific abnormalities involved.
The prevalence of heterotaxy syndrome is estimated to be 1 in 10,000 people worldwide. However, researchers suspect that the condition is underdiagnosed, and so it may actually be more common than this. Heterotaxy syndrome accounts for approximately 3 percent of all congenital heart defects. For reasons that are unknown, the condition appears to be more common in Asian populations than in North America and Europe. Recent studies report that in the United States, the condition occurs more frequently in children born to black or Hispanic mothers than in children born to white mothers.
Heterotaxy syndrome can be caused by mutations in many different genes. The proteins produced from most of these genes play roles in determining which structures should be on the right side of the body and which should be on the left, a process known as establishing left-right asymmetry. This process occurs during the earliest stages of embryonic development. Dozens of genes are probably involved in establishing left-right asymmetry; mutations in at least 20 of these genes have been identified in people with heterotaxy syndrome.  In some cases, heterotaxy syndrome is caused by mutations in genes whose involvement in determining left-right asymmetry is unknown. Rarely, chromosomal changes such as insertions, deletions, duplications, and other rearrangements of genetic material have been associated with this condition.  Heterotaxy syndrome can occur by itself, or it can be a feature of other genetic syndromes that have additional signs and symptoms. For example, at least 12 percent of people with a condition called primary ciliary dyskinesia have heterotaxy syndrome. In addition to abnormally positioned internal organs, primary ciliary dyskinesia is characterized by chronic respiratory tract infections and an inability to have children (infertility). The signs and symptoms of this condition are caused by abnormal cilia, which are microscopic, finger-like projections that stick out from the surface of cells. It appears that cilia play a critical role in establishing left-right asymmetry before birth.  Studies suggest that certain factors affecting a woman during pregnancy may also contribute to the risk of heterotaxy syndrome in her child. These include diabetes mellitus; smoking; and exposure to hair dyes, cocaine, and certain laboratory chemicals.  Some people with heterotaxy syndrome have no identified gene mutations or other risk factors. In these cases, the cause of the condition is unknown.
Most often, heterotaxy syndrome is sporadic, meaning that only one person in a family is affected. However, about 10 percent of people with heterotaxy syndrome have a close relative (such as a parent or sibling) who has a congenital heart defect without other apparent features of heterotaxy syndrome. Isolated congenital heart defects and heterotaxy syndrome may represent a range of signs and symptoms that can result from a particular genetic mutation; this situation is known as variable expressivity. It is also possible that different genetic and environmental factors combine to produce isolated congenital heart defects in some family members and heterotaxy syndrome in others.  When heterotaxy syndrome runs in families, it can have an autosomal dominant, autosomal recessive, or X-linked pattern of inheritance, depending on which gene is involved. Autosomal dominant inheritance means that one copy of the altered gene in each cell is sufficient to cause the disorder. Autosomal recessive inheritance means that both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition. In X-linked inheritance, the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes in each cell.  When heterotaxy syndrome occurs as a feature of primary ciliary dyskinesia, it has an autosomal recessive pattern of inheritance.
These resources address the diagnosis or management of heterotaxy syndrome:  - Boston Children's Hospital: Tests for Heterotaxy Syndrome  - Gene Review: Gene Review: Primary Ciliary Dyskinesia  - Genetic Testing Registry: Atrioventricular septal defect, partial, with heterotaxy syndrome  - Genetic Testing Registry: Heterotaxy syndrome   These resources from MedlinePlus offer information about the diagnosis and management of various health conditions:  - Diagnostic Tests  - Drug Therapy  - Surgery and Rehabilitation  - Genetic Counseling   - Palliative Care
Congenital bilateral absence of the vas deferens occurs in males when the tubes that carry sperm out of the testes (the vas deferens) fail to develop properly. Although the testes usually develop and function normally, sperm cannot be transported through the vas deferens to become part of semen. As a result, men with this condition are unable to father children (infertile) unless they use assisted reproductive technologies. This condition has not been reported to affect sex drive or sexual performance.  This condition can occur alone or as a sign of cystic fibrosis, an inherited disease of the mucus glands. Cystic fibrosis causes progressive damage to the respiratory system and chronic digestive system problems. Many men with congenital bilateral absence of the vas deferens do not have the other characteristic features of cystic fibrosis; however, some men with this condition may experience mild respiratory or digestive problems.
Mutations in the CFTR gene cause congenital bilateral absence of the vas deferens.  More than half of all men with this condition have mutations in the CFTR gene. Mutations in this gene also cause cystic fibrosis. When congenital bilateral absence of the vas deferens occurs with CFTR mutations, it is considered a form of atypical cystic fibrosis.  The protein made from the CFTR gene forms a channel that transports negatively charged particles called chloride ions into and out of cells. The flow of chloride ions helps control the movement of water in tissues, which is necessary for the production of thin, freely flowing mucus. Mucus is a slippery substance that lubricates and protects the linings of the airways, digestive system, reproductive system, and other organs and tissues.  Mutations in the CFTR gene disrupt the function of the chloride channels, preventing them from regulating the flow of chloride ions and water across cell membranes. As a result, cells in the male genital tract produce mucus that is abnormally thick and sticky. This mucus clogs the vas deferens as they are forming, causing them to deteriorate before birth.  In instances of congenital bilateral absence of the vas deferens without a mutation in the CFTR gene, the cause of this condition is often unknown. Some cases are associated with other structural problems of the urinary tract.
When this condition is caused by mutations in the CFTR gene, it is inherited in an autosomal recessive pattern. This pattern of inheritance means that both copies of the gene in each cell have a mutation. Men with this condition who choose to father children through assisted reproduction have an increased risk of having a child with cystic fibrosis. If congenital absence of the vas deferens is not caused by mutations in CFTR, the risk of having children with cystic fibrosis is not increased.