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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

Mitochondrial Complex 1 Deficiency, ACAD9-Related

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What is Mitochondrial Complex 1 Deficiency, ACAD9-Related?

Mitochondrial Complex 1 Deficiency, ACAD9-Related (also called Acyl-Coenzyme Dehydrogenase 9 Deficiency or Riboflavin-Responsive Complex 1 Deficiency) is an inherited disorder that causes repeated episodes of metabolic acidosis, a condition in which the blood becomes very acidic. Signs and symptoms vary from person to person but often start in infancy and include bouts of metabolic acidosis that can lead to swelling of the brain, vomiting, seizures, coma, and sometimes death. Children with the severe form of this condition who survive may have ongoing heart problems, liver failure, muscle weakness, and coordination problems. Some children have less severe symptoms that start later in childhood and include a general lack of energy and extreme tiredness after exercise. Although there is no cure for this condition, treatment with high doses of Vitamin B2 (Riboflavin) may be helpful in preventing or reducing some of the symptoms.

What causes Mitochondrial Complex 1 Deficiency, ACAD9-Related?

Mitochondrial Complex 1 Deficiency, ACAD9-Related is caused by a gene change, or mutation, in both copies of the ACAD9 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. 

Mitochondrial Complex 1 Deficiency, NDUFAF5-Related

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What is Mitochondrial Complex 1 Deficiency, NDUFAF5-Related?

Mitochondrial Complex 1 Deficiency, NDUFAF5-Related is an autosomal recessive disorder that causes abnormal function of the mitochondria, the energy-producing structures found in the cells of the body.  Symptoms can start in infancy, childhood, or not until later in adulthood.  Common symptoms include larger than normal head size, progressive loss of the white matter of the brain, delayed development, seizures, enlarged heart, vision loss, liver disease, kidney disease, muscle disease, and abnormal movements. Infants who show symptoms early in life usually have more severe disease and may have a shortened lifespan.

What causes Mitochondrial Complex 1 Deficiency, NDUFAF5-Related?

Mitochondrial Complex 1 Deficiency, NDUFAF5-Related is caused by a change, or mutation, in both copies of the NDUFAF5 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.

Mitochondrial Complex 1 Deficiency, NDUFS6-Related

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What is Mitochondrial Complex 1 Deficiency, NDUFS6-Related?

Mitochondrial Complex 1 Deficiency, NDUFS6-Related is an autosomal recessive disorder that causes abnormal function of the mitochondria, the energy-producing structures found in the cells of the body.  Symptoms can start in infancy, childhood, or not until later in adulthood.  Common symptoms include larger than normal head size, progressive loss of the white matter of the brain, seizures, enlarged heart, vision loss, liver disease, kidney disease, muscle disease, and abnormal movements. Infants who show symptoms early in life usually have more severe disease and may have a shortened lifespan.

What causes Mitochondrial Complex 1 Deficiency, NDUFS6-Related?

Mitochondrial Complex 1 Deficiency, NDUFS6-Related is caused by a change, or mutation, in both copies of the NDUFS6 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.

Mitochondrial Myopathy and Sideroblastic Anemia (MLASA1)

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What is Mitochondrial Myopathy and Sideroblastic Anemia (MLASA1)?

Mitochondrial Myopathy and Sideroblastic Anemia, also known as Myopathy, Lactic Acidosis, and Sideroblastic Anemia 1 (MLASA1) is an autosomal recessive disorder that causes extreme fatigue, breathing problems, muscle weakness with exercise (exercise intolerance), and a specific type of anemia known as sideroblastic anemia. Exercise intolerance often begins in childhood and worsens over time. Sideroblastic anemia, in which the bone marrow makes abnormally shaped red blood cells that have trouble carrying enough oxygen to the cells of the body, usually begins in adolescence. Delayed growth, facial abnormalities, and intellectual disability occur in some people but are less common.

What causes Mitochondrial Myopathy and Sideroblastic Anemia (MLASA1)?

Mitochondrial Myopathy and Sideroblastic Anemia (MLASA1) is caused by a change, or mutation, in both copies of the PUS1 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.

Mucolipidosis II/IIIA

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What is Mucolipidosis II/IIIA?

Mucolipidosis II/IIIA, also known as I-cell Disease or Pseudo-Hurler Polydystrophy, refers to two related autosomal recessive disorders that affect many parts of the body.  Signs and symptoms of Mucolipidosis II begin in infancy and include short stature, developmental delay, abnormalities of the bones and joints, and heart disease. Other symptoms may include recurrent respiratory and ear infections, breathing problems, vision problems, hearing loss, hernias, carpal tunnel syndrome, and thickened skin. Children lose developmental skills over time, symptoms worsen, and death usually occurs in childhood. In some cases, individuals with Mucolipidosis II 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.

Signs and symptoms of Mucolipidosis IIIA usually begin in early childhood and are milder than those of Mucolipidosis II.  Lifespan may be normal in individuals with Mucolipidosis IIIA and rare affected individuals do not show symptoms until adulthood.

What causes Mucolipidosis II/IIIA?

Mucolipidosis II/IIIA is caused by a gene change, or mutation, in both copies of the GNPTAB gene pair. These mutations cause the genes to not work properly or not work at all. Normal function of the GNPTAB gene pair is needed to break down and get rid of waste in the cells of the body. When both copies of the GNPTAB gene do not work correctly, it leads to the symptoms described above. 

Mucolipidosis III gamma

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What is Mucolipidosis III gamma?

Mucolipidosis III gamma is an autosomal recessive disorder that affects many parts of the body.  Signs and symptoms of Mucolipidosis type III gamma usually begin by the age of 3 and include short stature, unusual facial features, abnormalities and pain in the bones and joints, and heart disease. Some affected children have mild intellectual disability.  Symptoms worsen over time.  Most people with this condition live until adulthood but lifespan may be shortened.  Currently there is no cure for this condition and treatment is based on symptoms.

What causes Mucolipidosis III gamma?

Mucolipidosis III gamma is caused by a gene change, or mutation, in both copies of the GNPTG gene pair. These mutations cause the genes to not work properly or not work at all. Normal function of the GNPTG gene pair is needed to break down certain substances in the cells of the body. When both copies of the GNPTG gene do not work correctly, it leads to the symptoms described above. 

Mucolipidosis, Type IV

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What is Mucolipidosis, Type IV?

Mucolipidosis, Type IV is an autosomal recessive disorder in which affected infants and children have motor delay, severe intellectual disability, and vision problems that worsen over time.  Other common symptoms include weak muscle tone (hypotonia), problems eating and swallowing, limited speech, and problems with movement, especially of the hands.  Lifespan may be shortened although most people with this condition live into adulthood.  A small number of people with Mucolipidosis, Type IV have milder symptoms.  Currently there is no cure for this condition and treatment is based on symptoms.

What causes Mucolipidosis, Type IV?

Mucolipidosis, Type IV is caused by a gene change, or mutation, in both copies of the MCOLN1 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.

Mucopolysaccharidosis, Type I (Hurler Syndrome)

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What is Mucopolysaccharidosis, Type I (Hurler Syndrome)?

Mucopolysaccharidosis, Type I, also known as Hurler syndrome, is an autosomal recessive disorder that causes toxic buildup of certain types of sugars, called glycosaminoglycans, in the body.  There are mild and severe forms of Mucopolysaccharidosis, Type I.  Most children with Mucopolysaccharidosis, Type I have symptoms in the first years of life that may include progressive intellectual disability, large head size, coarse facial features, heart problems, bone problems, short stature, enlarged liver and spleen, frequent infections, vision problems, and breathing problems. Without treatment, children with this form of Mucopolysaccharidosis, Type I usually do not survive past childhood.  People with milder forms of this disorder usually live into adulthood and have a milder degree of intellectual disability. Treatment may include enzyme replacement therapy. 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 Mucopolysaccharidosis, Type I (Hurler Syndrome)?

Mucopolysaccharidosis, Type I is caused by a gene change, or mutation, in both copies of the IDUA gene pair.  These mutations cause the genes to not work properly or not work at all.  The function of the IDUA genes is to create an enzyme which breaks down long chain sugar molecules and clears them from the body.  When both copies of this gene do not work correctly, it causes buildup of certain sugars over time causing cell damage in many organs.  This leads to the symptoms described above.

Mucopolysaccharidosis, Type II (Hunter Syndrome)

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What is Mucopolysaccharidosis, Type II (Hunter Syndrome)?

Mucopolysaccharidosis, Type II (also called Hunter Syndrome) is an X-linked inherited disorder that affects many parts of the body. It occurs mainly in boys and very rarely affects girls. There are two forms of this disorder, a severe form as well as a mild form. Signs and symptoms of the severe form of Mucopolysaccharidosis, Type II start in early childhood and include intellectual decline and disability, heart disease, and respiratory problems. Signs and symptoms of mild form begin in late childhood or adolescence, progress more slowly, and intelligence is not affected.  Both forms of Mucopolysaccharidosis, Type II have symptoms that often include short stature, large head, large tongue, hearing loss, hoarse voice, spine problems, enlarged liver and spleen, heart problems, and breathing problems. Symptoms worsen over time and people with Mucopolysaccharidosis, Type II have a decreased lifespan with death usually occurring by early adulthood. Treatments are available to help lessen the severity of symptoms. 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 Mucopolysaccharidosis, Type II (Hunter Syndrome)?

Mucopolysaccharidosis, Type II is caused by a change, or mutation, in the IDS gene.  This mutation causes the gene to not work properly or not work at all.  When the IDS gene in a male does not work correctly, it leads to the symptoms described above. 

Mucopolysaccharidosis, Type IIIA (Sanfilippo A)

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What is Mucopolysaccharidosis, Type IIIA (Sanfilippo A)?

Mucopolysaccharidosis, Type IIIA (also called Sanfilippo A) is an autosomal recessive disorder that affects many parts of the body. Signs and symptoms of Mucopolysaccharidosis, Type IIIA usually begin in early childhood and include unusual facial features, a large head size, bone and joint abnormalities, intellectual disability, behavioral problems, sleep difficulties, and coordination and movement problems. Other symptoms include recurrent respiratory and ear infections, vision problems, hearing loss, and hernias. Children lose developmental skills over time, symptoms worsen, and lifespan is shortened with death usually occurring by early 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 Mucopolysaccharidosis, Type IIIA (Sanfilippo A)?

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

Mucopolysaccharidosis, Type IIIB (Sanfilippo B)

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What is Mucopolysaccharidosis, Type IIIB (Sanfilippo B)?

Mucopolysaccharidosis, Type IIIB (also called Sanfilippo B) is an autosomal recessive disorder that affects many parts of the body.  Signs and symptoms vary from person to person and usually start in childhood, although occasionally do not start until adulthood.  Typical symptoms include unusual facial features, large head size, bone and joint abnormalities, intellectual disability, behavioral problems, sleep difficulties, and coordination and movement problems. Other symptoms may include recurrent respiratory and ear infections, vision problems, hearing loss, and hernias.  Developmental skills are lost over time, symptoms worsen, and lifespan is usually shortened. 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 Mucopolysaccharidosis, Type IIIB (Sanfilippo B)?

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

Mucopolysaccharidosis, Type IIIC (Sanfilippo C)

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What is Mucopolysaccharidosis, Type IIIC (Sanfilippo C)?

Mucopolysaccharidosis, Type IIIC (also called Sanfilippo C) is an autosomal recessive disorder that affects many parts of the body. Signs and symptoms of Mucopolysaccharidosis, Type IIIC usually begin in early childhood and include unusual facial features, a large head size, bone and joint abnormalities, intellectual disability, behavioral problems, sleep difficulties, and coordination and movement problems. Other symptoms include recurrent respiratory and ear infections, vision problems, hearing loss, and hernias. Children lose developmental skills over time, symptoms worsen, and lifespan is shortened with death usually occurring by early 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 Mucopolysaccharidosis, Type IIIC (Sanfilippo C)?

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

Mucopolysaccharidosis, Type IIID (Sanfilippo D)

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What is Mucopolysaccharidosis, Type IIID (Sanfilippo D)?

Mucopolysaccharidosis (MPS), Type IIID (also called Sanfilippo D) is an autosomal recessive disorder that affects many parts of the body. Signs and symptoms vary from person to person and usually start in childhood, although occasionally do not start until adulthood. Typical symptoms include unusual facial features, large head size, bone and joint abnormalities, intellectual disability, behavioral problems, sleep difficulties, and coordination and movement problems. Other symptoms may include recurrent respiratory and ear infections, vision problems, hearing loss, and hernias. Developmental skills are lost over time, symptoms worsen, and lifespan is usually shortened. 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 Mucopolysaccharidosis, Type IIID (Sanfilippo D)?

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

Mucopolysaccharidosis, Type IVB/GM1 Gangliosidosis

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What is Mucopolysaccharidosis, Type IVB/GM1 Gangliosidosis?

Mucopolysaccharidosis (MPS), Type IVB (also called Morquio Syndrome) and GM1 Gangliosidosis are autosomal recessive disorders that affect many parts of the body. Both disorders are caused by mutations in the same gene but they have different signs and symptoms.

The more common disorder, GM1 Gangliosidosis, causes progressive loss of nerve cells in the brain and spine. The infantile form of GM1 Gangliosidosis causes weakened muscles, loss of motor skills, developmental delay and intellectual disability, clouding of the cornea of the eye and degeneration of the retina that causes vision loss, and enlargement of the liver, spleen and heart. Babies with this form usually die by early childhood. Some children with GM1 Gangliosidosis do not start showing symptoms until early childhood and do not have organ enlargement but still have loss of skills and a shortened lifespan. In rare cases symptoms do not start until the teenage or early adult years and include episodes of muscle spasms (dystonia), problems with walking and speech, enlarged heart, and memory loss; this adult-onset form is mostly seen in people of Japanese ancestry.

The less common disorder, MPS, Type IVB, causes skeletal abnormalities, and abnormal growth of bone and cartilage. Other signs and symptoms of MPS, Type IVB often include short stature, overly mobile joints, hearing loss, breathing problems, spinal cord problems, hernias, sleep apnea, heart disease, multiple cavities in the teeth, and clouding of the cornea of the eye. Intelligence is not affected. Lifespan is decreased in children with the early-onset form of MPS, Type IVB with death often occurring in late childhood or early teens. Lifespan may be near normal in people with the later-onset form. 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 Mucopolysaccharidosis, Type IVB /GM1 Gangliosidosis?

MPS, Type IVB and GM1 Gangliosidosis are each caused by a change, or mutation, in both copies of the GLB1 gene pair. These mutations cause the genes to not work properly or not work at all. When both copies of the GLB1 gene do not work correctly, it leads to the symptoms of either GM1 Gangliosidosis or MPS, Type IVB as described above.

Mucopolysaccharidosis, Type IX

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What is Mucopolysaccharidosis, Type IX?

Mucopolysaccharidosis, Type IX, also known as Hyaluronidase Deficiency, is a rare autosomal recessive disorder that affects many parts of the body.  Signs and symptoms begin in early childhood and include short stature, episodes of painful soft tissue masses that form around joints, and breakdown of the hip joint that worsens over time. Some children are born with a cleft palate and may have repeated ear infections. Intelligence is not affected. Currently there is no cure for this disorder and treatment is based on symptoms.

What causes Mucopolysaccharidosis, Type IX?

Mucopolysaccharidosis, Type IX is caused by a change, or mutation, in both copies of the HYAL1 gene pair. These mutations cause the genes to not work properly or not work at all.  When both copies of the HYAL1 gene do not work correctly, it leads to the symptoms described above.

Mucopolysaccharidosis, Type VI (Maroteaux-Lamy)

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What is Mucopolysaccharidosis, Type VI (Maroteaux-Lamy)?

Mucopolysaccharidosis, Type VI (also called Maroteaux-Lamy Syndrome) is an autosomal recessive disorder that affects many parts of the body. Signs and symptoms of Mucopolysaccharidosis, Type VI vary from person to person, often begin in early childhood, and include short stature, joint abnormalities, clouding of the cornea of the eye, large head, large tongue, hearing loss, hoarse voice, sleep disturbances, heart valve abnormalities, a buildup of fluid on the brain (hydrocephalus), hernias, and enlarged liver and spleen. Intelligence is not affected.  Symptoms worsen over time and, depending on the severity of the symptoms, lifespan may be shortened. Treatment is available to help minimize the severity of symptoms. 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 Mucopolysaccharidosis, Type VI (Maroteaux-Lamy)?

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

Multiple Sulfatase Deficiency

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What is Multiple Sulfatase Deficiency?

Multiple Sulfatase Deficiency (MSD) is a rare autosomal recessive disorder that causes problems in many parts of the body, but mainly in the brain, bones, and skin. Signs and symptoms vary from person to person. The most severe type of MSD, the ‘neonatal form’, has symptoms that begin shortly after birth and include seizures, movement problems, developmental delays, slow growth, excess hair, scaly skin (ichthyosis), scoliosis, other bone problems, and sometimes heart defects and/or enlarged liver and spleen. MRI scans show loss of white matter in the brain (leukodystrophy). Babies with the infantile form often die before the age of one. The most common form of MSD is called ‘late-infantile’ and has symptoms that usually begin by two years of age and include movement problems, progressive developmental delay, ichthyosis, and skeletal changes. Affected children lose developmental skills over time, symptoms worsen, and lifespan is shortened. There is also a rare form of MSD called ‘juvenile-onset’ with similar symptoms that typically begin between the ages of 2 and 4 that progress more slowly than the early-onset forms. Currently, there is no cure or specific treatment for any form of MSD.

What causes Multiple Sulfatase Deficiency?

Multiple Sulfatase Deficiency is caused by a change, or mutation, in both copies of the SUMF1 gene pair. These mutations cause the genes to not work properly or not work at all.  When both copies of the SUMF1 gene pair do not work correctly, it leads to the symptoms described above.

Muscle-Eye-Brain Disease, POMGNT1-Related

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What is Muscle-Eye-Brain Disease, POMGNT1-Related?

Muscle-Eye-Brain Disease, POMGNT1-Related is an autosomal recessive condition. It is one of a group of inherited disorders called dystroglycanopathies that affect many parts of the body. Signs and symptoms appear shortly after birth and include muscle weakness (hypotonia), eye abnormalities and vision problems, severe brain abnormalities, water on the brain (hydrocephalus), seizures, developmental delay, intellectual disability, and distinctive facial features. The symptoms and severity vary among affected children. Lifespan is often shortened with death occurring from early childhood to the early teens. There is no cure or specific treatment for this disorder.

Occasionally, mutations in the same gene cause a related form of dystroglycanopathy, either Muscular Dystrophy-Dystroglycanopathy, Type C3 (Limb-Girdle) (MDDGC3) or Muscular Dystrophy-Dystroglycanopathy (Congenital with Mental Retardation) Type B3 (MDDGB3). Even more rarely, a separate condition called Retinitis Pigmentosa 76 may occur that affects only vision.

What causes Muscle-Eye-Brain Disease, POMGNT1-Related?

Muscle-Eye-Brain Disease, POMGNT1-Related is caused by a change, or mutation, in both copies of the POMGNT1 gene pair. These mutations cause the genes to not work properly or not work at all. When both copies of the POMGNT1 gene do not work correctly, it leads to the symptoms described above.

Myoneurogastrointestinal Encephalopathy (MNGIE)

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What is Myoneurogastrointestinal Encephalopathy (MNGIE)?

Myoneurogastrointestinal Encephalopathy (MNGIE) is an autosomal recessive disorder that affects digestion and nerve function.  The main symptom is ‘gastrointestinal dysmotility’, the inability to move food through the digestive tract. This can cause pain, discomfort, nausea, diarrhea, and weight loss. Some people with MNGIE also have tingling, numbness, and weakness in their limbs, especially in their hands and feet.  Weak muscles in or around the eyes, and hearing loss may also occur. Symptoms of MNGIE usually begin before age 20, but can appear in earlier in childhood or late into adulthood.  Currently there is no cure for this disorder and treatment is based on symptoms.

What causes Myoneurogastrointestinal Encephalopathy (MNGIE)?

MNGIE is caused by a gene change, or mutation, in both copies of the TYMP gene pair.  These mutations cause the genes to not work properly or not work at all.  Normal function of the TYMP gene is important in helping the mitochondria (the ‘powerhouses’ in the cells of the body) create energy that the cells can use.  When both copies of the TYMP gene pair do not work correctly, it leads to the symptoms described above. 

Myotubular Myopathy, X-Linked

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What is Myotubular Myopathy, X-Linked?

Myotubular Myopathy, X-Linked is an X-linked disorder that occurs mainly in males and causes severe muscle weakness and poor muscle tone starting at birth. Male infants and boys with Myotubular Myopathy, X-Linked have feeding problems, severe breathing problems, and developmental delays. Muscle weakness may also lead to abnormal curvature of the spine, hip and knee contractures, and fragile bones. Some affected boys may also have weak facial muscles, trouble controlling eye movements, absent reflexes, recurrent ear and respiratory infections, or seizures.  Death usually occurs in early childhood.  Currently there is no cure or specific treatment for this condition.

What causes Myotubular Myopathy, X-Linked?

Myotubular Myopathy, X-Linked is caused by a change, or mutation, in the MTM1 gene. This mutation causes the gene to not work properly or not work at all. The MTM1 gene is important for the development and health of the muscles.  When this gene is not working correctly in a male, it causes the symptoms described above. Most female carriers do not have symptoms of Myotubular Myopathy; although rare female carriers are found to have some symptoms, which are generally less severe than those seen in affected males.

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