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Disease List:

3 6 A B C D E F G H I J K L M N O P R S T U V W Z

N-acetylglutamate Synthase Deficiency

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What is N-acetylglutamate Synthase Deficiency?

N-acetylglutamate Synthase Deficiency is an autosomal recessive disorder that causes an abnormal buildup of nitrogen, in the form of ammonia, in the blood. Too much ammonia is toxic to the body and causes damage to the brain and nervous system. If the condition is not treated, signs and symptoms often appear early in infancy.  Symptoms include lethargy, feeding and breathing problems, inability to control body temperature, seizures, abnormal movements, and, sometimes, coma.  If left untreated, the condition can lead to developmental delays and intellectual disability.  Some people with this condition have symptoms, often triggered by stress or illness, which do not begin until later in life.  People with the later-onset form have repeated episodes that may include vomiting, confusion, problems with coordination, or coma.  Treatment is needed to prevent or reduce symptoms and includes both a special low protein medical diet and medications to reduce the amount of nitrogen in the body. 

What causes N-acetylglutamate Synthase Deficiency?

N-acetylglutamate Synthase Deficiency is caused by a gene change, or mutation, in both copies of the NAGS gene pair.  These mutations cause the genes to not work properly or not work at all.  The NAGS genes make an enzyme that helps the body get rid of excess nitrogen.  When both copies of the NAGS gene pair do not work correctly, ammonia builds up in the body and leads to the symptoms described above. 

Nemaline Myopathy, NEB-Related

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What is Nemaline Myopathy, NEB-Related?

Nemaline Myopathy, NEB-Related is an autosomal recessive disorder that affects skeletal muscles, mainly those in the face, neck, arms, legs, and the muscles that control breathing.  The condition causes both muscle weakness and problems with muscle contraction.  Signs and symptoms are caused by abnormal thread-like rods (“nemaline bodies”) in the muscle cells. Newborns have poor muscle tone (hypotonia) and may have feeding and breathing problems.  Problems with swallowing and speech are also common. Most children with Nemaline Myopathy, NEB-Related are able to walk, although some may begin walking later than usual, and some people eventually need a wheelchair.  Intelligence is not affected. Lifespan is often normal; however, in severe cases, life-threatening breathing problems and lung infections may occur.  Currently there is no cure for this condition and treatment is based on symptoms.

What causes Nemaline Myopathy, NEB-Related?

Nemaline Myopathy, NEB-Related is caused by a gene change, or mutation, in both copies of the NEB gene pair.  These mutations cause the genes to not work properly or not work at all.  Normal function of the NEB genes is important for normal muscle contractions. When both copies of the NEB gene pair do not work correctly, muscles are not able to contract properly, which leads to the symptoms described above. 

Neuronal Ceroid Lipofuscinosis, CLN5-Related

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What is Neuronal Ceroid Lipofuscinosis, CLN5-Related?

Neuronal Ceroid Lipofuscinosis, CLN5-Related (also known as CLN5 Disease) is autosomal recessive.  It is one of a group of inherited disorders that affect the nervous system as well as other parts of the body. Signs and symptoms of Neuronal Ceroid Lipofuscinosis, CLN5-Related begin in late infancy or early childhood and include coordination and movement problems, epileptic seizures, and vision loss. Over time, children show intellectual decline and lose developmental and motor skills. Wheelchair assistance is usually needed by late childhood.  Symptoms worsen with time and lifespan is shortened with death usually occurring by adolescence.  In rare cases, symptoms do not begin until adulthood and may include loss of memory and motor skills along with behavior changes.  Currently there is no cure or specific treatment for this disorder. 

What causes Neuronal Ceroid Lipofuscinosis, CLN5-Related?

Neuronal Ceroid Lipofuscinosis, CLN5-Related is caused by a change, or mutation, in both copies of the CLN5 gene pair. These mutations cause the genes to not work properly or not work at all.  When both copies of the CLN5 gene do not work correctly, it leads to the symptoms described above.

Neuronal Ceroid Lipofuscinosis, CLN6-Related

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What is Neuronal Ceroid Lipofuscinosis, CLN6-Related?

Neuronal Ceroid Lipofuscinosis, CLN6-Related (also known as CLN6 Disease) is autosomal recessive.  It is one of a group of inherited disorders that affect the nervous system as well as other parts of the body. Signs and symptoms of Neuronal Ceroid Lipofuscinosis, CLN6-Related may first begin in early childhood or not until adulthood. Initial symptoms of the childhood-onset form include epileptic seizures and vision loss. Symptoms of the adulthood-onset form include coordination and movement problems and epileptic seizures without vision loss. Over time, both children and adults with Neuronal Ceroid Lipofuscinosis, CLN6-Related have intellectual decline and lose developmental and motor skills. Symptoms worsen with time and lifespan is shortened. Currently there is no cure or specific treatment for this disorder.

What causes Neuronal Ceroid Lipofuscinosis, CLN6-Related?

Neuronal Ceroid Lipofuscinosis, CLN6-Related is caused by a change, or mutation, in both copies of the CLN6 gene pair. These mutations cause the genes to not work properly or not work at all.  When both copies of the CLN6 gene do not work correctly, it leads to the symptoms described above.

Neuronal Ceroid Lipofuscinosis, CLN8-Related

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What is Neuronal Ceroid Lipofuscinosis, CLN8-Related?

Neuronal Ceroid Lipofuscinosis, CLN8-Related (also known as CLN8 Disease) is autosomal recessive.  It is one of a group of inherited disorders that affect the nervous system as well as other parts of the body. Signs and symptoms of Neuronal Ceroid Lipofuscinosis, CLN8-Related begin in early childhood and include epileptic seizures along with coordination and movement problems. Over time, affected children have vision loss and intellectual decline and lose developmental and motor skills. Symptoms worsen with time and lifespan is often shortened. Some people have a milder form of this condition, sometimes called Northern Epilepsy, which has the same symptoms as described above but with slower progression. People with Northern Epilepsy may live to late adulthood. Currently there is no cure or specific treatment for this disorder.

What causes Neuronal Ceroid Lipofuscinosis, CLN8-Related?

Neuronal Ceroid Lipofuscinosis, CLN8-Related is caused by a change, or mutation, in both copies of the CLN8 gene pair.  These mutations cause the genes to not work properly or not work at all.  When both copies of the CLN8 gene do not work correctly, it leads to the symptoms described above.   It is sometime, but not always, possible to tell whether a specific mutation in the CLN8 gene will cause the severe form of Neuronal Ceroid Lipofuscinosis, CLN8-Related or the milder form, Northern Epilepsy. 

Neuronal Ceroid Lipofuscinosis, MFSD8-Related

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What is Neuronal Ceroid Lipofuscinosis, MFSD8-Related?

Neuronal Ceroid Lipofuscinosis, MFSD8-Related (also known as CLN7 Disease) is autosomal recessive.  It is one of a group of inherited disorders that affect the nervous system as well as other parts of the body. Signs and symptoms of Neuronal Ceroid Lipofuscinosis, MFSD8-Related begin in early childhood and include epileptic seizures along with coordination and movement problems.  Over time, affected children have vision loss and intellectual decline and lose developmental and motor skills. Symptoms worsen with time and lifespan is shortened. Currently there is no cure or specific treatment for this disorder.

What causes Neuronal Ceroid Lipofuscinosis, MFSD8-Related?

Neuronal Ceroid Lipofuscinosis, MFSD8-Related is caused by a change, or mutation, in both copies of the MFSD8 gene pair. These mutations cause the genes to not work properly or not work at all.  When both copies of the MFSD8 gene do not work correctly, it leads to the symptoms described above.

Neuronal Ceroid Lipofuscinosis, PPT1-Related

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What is Neuronal Ceroid Lipofuscinosis, PPT1-Related?

Neuronal Ceroid Lipofuscinosis, PPT1-Related (also known as CLN1 Disease) is autosomal recessive.  It is one of a group of inherited disorders that affect the nervous system as well as other parts of the body. Signs and symptoms of Neuronal Ceroid Lipofuscinosis, PPT1-Related often begin in infancy and include coordination and movement problems, epileptic seizures, smaller than average head size (microcephaly), and developmental delay. Over time, affected children have vision loss and intellectual decline and lose developmental and motor skills. Symptoms worsen with time and lifespan is shortened with death usually occurring in childhood.  Some children do not start developing symptoms until early childhood and may survive into their teens. There is also is a less common adult-onset form of Neuronal Ceroid Lipofuscinosis, PPT1-Related, sometimes called Kufs Disease, with symptoms that include seizures, coordination and movement problems, and intellectual decline with shortened lifespan. Currently there is no cure or specific treatment for Neuronal Ceroid Lipofuscinosis, PPT1-Related.   

What causes Neuronal Ceroid Lipofuscinosis, PPT1-Related?

Neuronal Ceroid Lipofuscinosis, PPT1-Related is caused by a change, or mutation, in both copies of the PPT1 gene pair.  These mutations cause the genes to not work properly or not work at all.  When both copies of the PPT1 gene do not work correctly, it leads to the symptoms described above.

Neuronal Ceroid Lipofuscinosis, TPP1-Related

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What is Neuronal Ceroid Lipofuscinosis, TPP1-Related?

Neuronal Ceroid Lipofuscinosis, TPP1-Related (also known as CLN2 Disease, Late-Infantile Neuronal Ceroid Lipofuscinosis, or Juvenile Batten Disease) is autosomal recessive.  It is one of a group of inherited disorders that affect the nervous system as well as other parts of the body. Signs and symptoms of Neuronal Ceroid Lipofuscinosis, TPP1-Related typically begin in early childhood with epileptic seizures. Over time, affected children have vision loss and intellectual decline, develop a movement disorder, and lose developmental and motor skills. Symptoms worsen with time and lifespan is shortened with death usually occurring by adolescence or early adulthood.  Currently there is no cure or specific treatment for this disorder. 

Very rarely, mutations in the same gene cause a different inherited disorder called Spinocerebellar Ataxia, Type 7 (SCA7).

What causes Neuronal Ceroid Lipofuscinosis, TPP1-Related?

Neuronal Ceroid Lipofuscinosis, TPP1-Related is caused by a change, or mutation, in both copies of the TPP1 gene pair.  These mutations cause the genes to not work properly or not work at all.  When both copies of the TPP1 gene do not work correctly, it leads to the symptoms described above.

Niemann-Pick Disease, Type C1/D

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What is Niemann-Pick Disease, Type C1/D?

Niemann-Pick Disease, Type C1/D is one of a group of autosomal recessive disorders that affect many parts of the body. Signs and symptoms of Niemann-Pick Disease, Type C1/D often begin in childhood and include problems with coordination and muscle movements, seizures, liver and lung disease, abnormal eye movements (supranuclear palsy), and poor muscle tone. Other symptoms may include intellectual disability, seizures, and problems with speech and swallowing that worsen over time. Lifespan is shortened with death often occurring by early adulthood.  In rare cases, symptoms do not occur until adulthood and may also include dementia and behavior changes.  Currently there is no cure or specific treatment for this disorder.

What causes Niemann-Pick Disease, Type C1/D?

Niemann-Pick Disease, Type C1/D is caused by a change, or mutation, in both copies of the NPC1 gene pair.  These mutations cause the genes to not work properly or not work at all.  Normal function of the NPC1 gene pair is needed for normal transport of substances within the cells of the body. When both copies of the NPC1 gene do not work correctly, it leads to the symptoms described above.

Niemann-Pick Disease, Type C2

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What is Niemann-Pick Disease, Type C2?

Niemann-Pick Disease, Type C2 is one of a group of autosomal recessive disorders that affect many parts of the body. Signs and symptoms of Niemann-Pick Disease, Type C2 begin in childhood and include problems with coordination and muscle movements, seizures, liver and lung disease, abnormal eye movements (supranuclear palsy), and poor muscle tone. Other symptoms may include intellectual disability and problems with speech and swallowing that worsen over time. Lifespan is shortened with death often occurring by early adulthood. Currently there is no cure or specific treatment for this disorder.

What causes Niemann-Pick Disease, Type C2?

Niemann-Pick Disease, Type C2 is caused by a change, or mutation, in both copies of the NPC2 gene pair.  These mutations cause the genes to not work properly or not work at all.  When both copies of the NPC2 gene do not work correctly, it leads to the symptoms described above.

Niemann-Pick Disease, Types A/B

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What is Niemann-Pick Disease, Types A/B?

Niemann-Pick Disease, Types A/B (A and B) refers to two related autosomal recessive disorders that affect many parts of the body.  These conditions result in a build-up of specific types of fats in body cells, tissues, and blood that worsens over time.  Symptoms resulting from the buildup of fats include breathing problems, enlarged liver and spleen, and loss of motor skills.  Niemann-Pick Disease usually results in a shortened lifespan.  Children with Niemann-Pick Disease, Type A have progressive loss of cognitive skills and the condition is typically fatal in early childhood.  Children with Niemann-Pick Disease, Type B often survive into adulthood. In some cases, affected individuals have been treated with stem cell transplantation from cord blood or bone marrow. Couples at risk of having an affected child may consider cord blood banking, as siblings have a higher chance of being a match for stem cell transplantation than a non-related individual.

What causes Niemann-Pick Disease, Types A/B?

Niemann-Pick Disease, Types A/ B are caused by gene changes, or mutations, in both copies of the SMPD1 gene pair.  These mutations cause the genes to not work properly or not work at all.  When both copies of this gene do not work correctly, it leads to the symptoms described above.

Nijmegen Breakage Syndrome

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What is Nijmegen Breakage Syndrome?

Nijmegen Breakage Syndrome is an autosomal recessive disorder that affects many parts of the body. Signs and symptoms of this disorder begin in infancy and include smaller than average head size (microcephaly), an increased risk for cancer of the immune system (non-Hodgkin’s and other types of lymphoma), increased risk for solid tumor cancers, some degree of intellectual disability, short stature, reproductive problems in females, repeated upper respiratory infections, and distinct facial features. Children lose developmental skills over time, symptoms worsen, and lifespan may be shortened. People with Nijmegen Breakage Syndrome are sensitive to the effects of radiation on the body and should minimize exposure if possible. Currently there is no cure for this disorder and treatment is based on symptoms.

Individuals who are carriers for Nijmegen Breakage Syndrome do not have Nijmegen Breakage Syndrome themselves.  However, initial studies suggest that carriers may be at increased risk to develop certain types of cancer.  Further studies need to be done to determine the actual risk for cancer in carriers of Nijmegen Breakage Syndrome and which type of cancers are included in the risk.

What causes Nijmegen Breakage Syndrome?

Nijmegen Breakage Syndrome is caused by a change, or mutation, in both copies of the NBN gene pair. These mutations cause the genes to not work properly or not work at all.  Normal function of the NBN gene pair is needed for repair of damaged DNA within the cells of the body. When both copies of the NBN gene do not work correctly, it leads to the symptoms described above.

Non-Syndromic Hearing Loss, GJB2-Related

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What is Non-Syndromic Hearing Loss, GJB2-Related?

Non-Syndromic Hearing Loss, GJB2-Related (also called DFNB1) is an autosomal recessive disorder that causes early-onset hearing loss. “Non-syndromic’ means that no other parts of the body are affected, making hearing loss the only symptom of this condition. In Non-Syndromic Hearing Loss, GJB2-Related, hearing loss is typically present at birth (congenital). However, some children have normal hearing at birth and develop hearing loss during childhood. The severity varies from mild to profound sensorineural hearing loss. The treatment for hearing loss includes hearing aids and, in some cases, cochlear implants.  Non-Syndromic Hearing Loss, GJB2-Related does not cause other health problems.

What causes Non-Syndromic Hearing Loss, GJB2-Related?

Non-Syndromic Hearing Loss, GJB2-Related is caused by a gene change, or mutation, in both copies of the GJB2 gene pair (also known as DFNB1).  These mutations cause the genes to not work properly or not work at all.  The function of the GJB2 gene is to make a protein that is important for hearing. When both copies of the GJB2 gene do not work correctly, it leads to Non-Syndromic Hearing Loss, GJB2-Related.

Odonto-Onycho-Dermal Dysplasia/Schopf-Schulz-Passarge Syndrome

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What is Odonto-Onycho-Dermal Dysplasia/Schopf-Schulz-Passarge Syndrome?

Odonto-Onycho-Dermal Dysplasia (OODD) and Schopf-Schulz-Passarge Syndrome (SSPS) are autosomal recessive types of Ectodermal Dysplasias, a group of inherited disorders that affect the skin, sweat glands, teeth, and nails. OODD and SSPS have similar signs and symptoms including dry and thin body and scalp hair, undeveloped and absent teeth, fingernail abnormalities, excessive or absent sweating, hardening of the skin, especially on the palms of the hands or soles of the feet, and sometimes blistering rashes. SSPS may also cause benign eyelid cysts and sometimes other skin tumors. Many of the symptoms start in childhood; however, some may not show up until adulthood. Currently there is no cure for these conditions and treatment is based on symptoms. Carriers may have no symptoms or may have mild features such as dry skin, nail abnormalities, thin hair, and/or one or more misshapen or missing permanent teeth.

What causes Odonto-Onycho-Dermal Dysplasia /Schopf-Schulz-Passarge Syndrome?

OODD and SSPS are caused by a gene change, or mutation, in both copies of the WNT10A gene pair. These mutations cause the genes to not work properly or not work at all. When both copies of this gene do not work correctly, it leads to the symptoms of one of these disorders. 

Omenn Syndrome, RAG2-Related

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What is Omenn Syndrome, RAG2-Related?

Omenn Syndrome, RAG2-Related, an autosomal recessive condition, is one of a group of inherited disorders called Severe Combined Immunodeficiency (SCID). People with Omenn Syndrome have immune system problems that prevent their body from fighting off infections. Signs and symptoms begin in infancy and include life-threatening infections, failure to grow and gain weight at the expected rate, severe reddened and peeling skin, chronic diarrhea, and enlarged liver and spleen. Infants and children with this condition often die young. In some cases, affected individuals have been treated with stem cell transplantation from cord blood or bone marrow. Couples at risk of having an affected child may consider cord blood banking, as siblings have a higher chance of being a match for stem cell transplantation than a non-related individual.

Rarely, mutations in the same gene pair that cause Omenn Syndrome cause a related type of autosomal recessive SCID, either Combined Cellular and Humoral Immune Defects with Granulomas or a more severe type of SCID called SCID T negative, B negative, NK positive.

What causes Omenn Syndrome, RAG2-Related?

Omenn Syndrome, RAG2-Related is caused by a gene change, or mutation, in both copies of the RAG2 gene pair. These mutations cause the genes to not work properly or not work at all. Normal function of the RAG2 gene pair is important for the health of the immune system. When both copies of the RAG2 gene do not work properly, it leads to the symptoms described above. 

Ornithine Aminotransferase Deficiency

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What is Ornithine Aminotransferase Deficiency?

Ornithine Aminotransferase Deficiency, also known as Gyrate Atrophy of the Choroid and Retina, is an autosomal recessive disorder that causes vision loss.  Loss of eyesight is caused by damage to the parts of the eye called the choroid and retina.  Signs and symptoms usually begin in late childhood and include myopia (nearsightedness) and night blindness.  Vision symptoms worsen with age and can include blindness and cataracts by age fifty. Mild muscle weakness can also occur. Occasionally, affected infants will have high levels of ammonia in the blood that can lead to feeding problems, vomiting, seizures, and, if untreated, may lead to coma.  Medical treatment can correct the high ammonia levels and the episodes stop occurring after infancy.  People with this condition usually have normal intelligence but some have mild to moderate intellectual disability.

What causes Ornithine Aminotransferase Deficiency?

Ornithine Aminotransferase Deficiency is caused by a gene change, or mutation, in both copies of the OAT gene pair. These mutations cause the genes to not work properly or not work at all. Normal function of the OAT genes is important for the health of the eyes and nervous system.  When both copies of the OAT gene do not work correctly, it leads to the symptoms described above. 

Ornithine Transcarbamylase Deficiency

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What is Ornithine Transcarbamylase Deficiency?

Ornithine Transcarbamylase (OTC) Deficiency is an X-linked inherited disorder that affects males more often than females.  OTC Deficiency causes ammonia to build up in the blood. Ammonia is formed when protein from food is broken down in the body. When ammonia levels become too high, they cause damage to the body. Symptoms of OTC Deficiency most often begin in the first few days after birth. Infants with OTC Deficiency may have low energy (lethargic), be unwilling to eat, have vomiting, and have problems with breathing or body temperature. If untreated, symptoms may worsen to include seizures, muscle weakness, swelling of the brain, coma, or death within the first few weeks of life. 

Less commonly, symptoms of OTC Deficiency can develop later in infancy, childhood, or adulthood. For those with later onset disease, symptoms can include intellectual disability, enlarged liver or liver disease, dry and brittle hair, avoidance of meat or other high protein foods, and episodes of high ammonia in the blood which can be life threatening if not treated promptly.  Rarely, symptoms do not occur until adulthood and may include migraines, nausea, coordination difficulties, blurred vision, confusion, and hallucinations

When OTC Deficiency is detected early and proper treatment is started immediately, affected children are more likely to be able to live longer lives with improved growth and development. However, even with treatment, some children may still have learning disabilities and/or tight muscles (spasticity).

What causes Ornithine Transcarbamylase Deficiency?

Ornithine Transcarbamylase (OTC) Deficiency is caused by a change, or mutation, in the OTC gene.  This mutation causes the gene to not work properly or not work at all. Males with OTC Deficiency do not make an enzyme that helps with the breakdown of nitrogen in the liver. When nitrogen is not broken down, it builds up in the blood as ammonia and causes the symptoms described above. 

Some females who are carriers for OTC Deficiency have some symptoms of the disorder, although they are usually milder than those seen in affected males. Female carriers may need special medical care during any pregnancies, as some carriers develop high ammonia levels during pregnancy or after delivery. 

Osteopetrosis, Infantile Malignant, TCIRG1-Related

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What is Osteopetrosis, Infantile Malignant, TCIRG1-Related?

Osteopetrosis, Infantile Malignant, TCIRG1-Related is a severe autosomal recessive type of Osteopetrosis, a group of disorders that cause bones to become overly dense and fracture easily. Symptoms are usually seen by early infancy and include multiple bone fractures and dense skull bones which often harm nerves in the head and face. The nerve damage may result in loss of vision, hearing, and facial movement. Bones are easily fractured, even with minor falls or stress. Children with Osteopetrosis, Infantile Malignant, TCIRG1-Related may also have reduced bone marrow function which can cause severe anemia and repeated infections. Slow growth, short stature, and enlarged spleen and liver are also common. Some children also have brain abnormalities, seizures and intellectual disability, although this is less common. In some cases, affected individuals have been treated with stem cell transplantation from cord blood or bone marrow. Couples at risk of having an affected child may consider cord blood banking, as siblings have a higher chance of being a match for stem cell transplantation than a non-related individual.

What causes Osteopetrosis, Infantile Malignant, TCIRG1-Related?

Osteopetrosis, Infantile Malignant, TCIRG1-Related is caused by a gene change, or mutation, in both copies of the TCIRG1 gene pair. These mutations cause the genes to not work properly or not work at all. The function of the TCIRG1 gene is to help with bone development. When both copies of the TCIRG1 gene pair do not work correctly, it leads to the symptoms described above.

Pendred Syndrome

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What is Pendred Syndrome?

Pendred Syndrome is an autosomal recessive disorder that causes hearing loss and growths on the thyroid gland called goiters.  Most children with Pendred Syndrome are either born with or develop sudden severe hearing loss by 3 years of age.  Thyroid goiters, which do not usually cause problems with thyroid function, develop in late childhood or early adulthood.  Other symptoms may include difficulties with balance or other inner ear abnormalities.  Some children have a slightly different form of this disorder, sometimes called DFNB4, which includes hearing loss, balance problems, and inner ear abnormalities, but no thyroid goiters. 

What causes Pendred Syndrome?

Pendred Syndrome is caused by a gene change, or mutation, in both copies of the SLC26A4 gene pair. These mutations cause the genes to not work properly or not work at all.  When both copies of the SLC26A4 gene do not work properly, it leads to the symptoms described above. 

Phenylketonuria

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What is Phenylketonuria?

Phenylketonuria (PKU) is an autosomal recessive disorder in which the body is unable to breakdown a building block of protein called phenylalanine. When toxic levels of phenylalanine buildup in the body it causes problems for the brain, nervous system, and other parts of the body.  If the condition is not treated, children with Phenylketonuria have intellectual disability, developmental delay, seizures, skin problems, and psychiatric problems.  Lifelong dietary treatment with a diet low in phenylalanine is needed to treat Phenylketonuria.  With treatment people with Phenylketonuria can lead healthy lives.  Other forms of Phenylketonuria called variant PKU and non-PKU hyperphenylalaninemia can be less severe, and have a lower risk for brain and health problems. Some people with very mild cases may not need treatment with a low phenylalanine diet.

What causes Phenylketonuria?

Phenylketonuria is caused by a gene change, or mutation, in both copies of the PAH gene pair. These mutations cause the genes to not work properly or not work at all. Normal function of the PAH genes is important for breaking down phenylalanine from the diet. When both copies of the PAH gene do not work correctly, it leads to the symptoms described above. 

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