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Diseases Studied

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CDG is a large group of rare, inherited disorders that affect a complex process in the body called glycosylation. Most children who have CDG have neurological issues and symptoms, developmental problems, growth delays and problems with organs not working like they should. CDG is not just one disorder, but rather, a group of disorders. There are many types.

Symptoms

Symptoms vary depending on the type and sub-type of the diagnosis. They also vary among family members with the same type. Symptoms can range from mild to severe. CDG can affect every body system. Because the condition is very rare, only a few people have each type and sub-type. This makes it hard for health care providers to have a complete list of symptoms. Not everyone has every symptom. Some have serious medical conditions which can be life-threatening.

Symptoms may include neurological problems (developmental delays, cognitive impairment, seizures, ataxia, dysarthria, esotropia), growth problems (failure to thrive, growth delays), organ issues (gastrointestinal symptoms such as diarrhea and vomiting, liver, heart), endocrine problems (hypothyroidism, hypoglycemia, hyperinsulinism, growth hormone deficiency), skeletal and joint problems (scoliosis, joint problems), hematologic problems (blood clotting issues, thrombosis), and general problems (severe or long lasting infections, swelling of skin and fluid collection around organs).

CDG is usually diagnosed at a young age. Children with CDG are often mistakenly diagnosed with other conditions. This is because their symptoms are similar to symptoms of other conditions. Some are mistakenly diagnosed with cerebral palsy or other neurological or genetic disorders. An important part of diagnosis is ruling out other conditions. Types of testing may include genetic testing (most reliable way), Blood testing to check for missing sugar building blocks on hormone proteins, coagulation factors, transport proteins, and elevated liver enzymes (ALT and AST)), transferrin glycosylation testing (to check for missing or incomplete sugar chains, and additional testing (such as liver ultrasounds, x-rays, MRIs, etc.).

Although there is currently no cure for CDG, there are many treatments and therapies available. The goal of these treatments is to treat the symptoms and the problems caused by the condition. This type of treatment is called supportive therapy. Supportive therapy may include physical therapy, speech therapy, occupational therapy, special diets/supplements, seizure management, heart medication, hormone supplements for growth, antibiotics for infection, and/or organ transplants.

Learn More About Specific Disorders

Also known as Congenital Disorder of Glycosylation Type Ig

A rare, inherited condition caused by a dysfunctional enzyme that cannot add mannose to proteins or fats. Symptoms manifest during infancy or early childhood, including failure to thrive, decreased muscle tone, developmental delay, intellectual disability, seizures, skeletal abnormalities, unusual facial features, sensorineural hearing loss (hearing loss caused by damage to the inner ear or the nerve from the ear to the brain), and heart muscle weakness.

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Also known as Congenital Disorder of Glycosylation Type Is

A rare, X-linked condition caused by new genetic (de novo) mutations affecting N-linked glycosylation. Symptoms manifest during infancy and include intractable seizures, extremity swelling, recurrent infections, bleeding problems, an enlarged liver, a small head, severe developmental delay, intellectual disability, and affected vision.

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Also known as Congenital Disorder of Glycosylation Type Id

A rare, multisystemic disorder beginning in infancy. It is characterized by severe neurological involvement, such as decreased muscle tone, developmental delay, intellectual disability, hearing loss, progressive brain atrophy, seizures, unusual facial features, vision problems, recurrent infections, and musculoskeletal, heart, lung, kidney, and urogenital abnormalities.

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Also known as Congenital Disorder of Glycosylation Type 1c

A rare, multisystemic, inherited condition, manifesting in infancy, caused by N-linked glycosylation disruption. Symptoms include failure to thrive, hypotonia (low muscle tone), developmental delay, intellectual disability, sleep, speech, and behavioral problems, seizures, ataxia (impaired balance or coordination), temporary paralysis, vision and hearing loss, liver disease, and heart muscle weakness.

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Also known as Congenital Disorder Of Glycosylation Type Ih

ALG8-CDG is an inherited condition that affects many parts of the body. Individuals with ALG8-CDG typically develop signs and symptoms of the condition during infancy. All affected individuals present with variable combinations of neurological abnormalities, including decreased muscle tone (hypotonia), developmental delay, a lack of muscle control or coordination of voluntary movements (ataxia), and seizure disorders.

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Also known as Congenital Disorder Of Glycosylation Type Iis

ATP6AP1-CDG is rare X-linked disorder affects primarily males. Currently, thirty individuals with ATP6AP1-CDG are reported in medical literature. The signs and symptoms typically develop during infancy and involve many body systems.

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Also known as Congenital Disorder Of Glycosylation Type Iir

ATP6AP2-CDG is very rare X-linked disorder that affect primarily males. Only few patients are reported in the medical literature. Signs and symptoms develop during early infancy.

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Also known as Carbohydrate Deficient Glycoprotein Syndrome Type 1j

A rare, inherited condition primarily affecting the nervous system caused by N-linked glycosylation disruption. Symptoms typically manifest in infancy with two phenotypes: congenital myasthenia syndrome (CMS) and encephalopathy. Characteristics are muscle weakness, hypotonia (low muscle tone), developmental delay, cognitive and speech impairments, and seizures.

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Also known as ER Degradation Enhancing Alpha-Mannosidase Like Protein 3

A rare, multisystemic, inherited condition caused by an abnormal protein which cannot effectively target misfolded glycoproteins. Symptoms manifest in infancy and childhood, including intellectual disability, developmental and speech delays, mild facial abnormalities, hypotonia (low muscle tone), behavioral problems, failure to thrive, and age-resolving central apnea.

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Also known as FUT8 Deficiency

A rare, multisystemic, inherited disorder caused by an abnormal enzyme which disrupts N-linked glycosylation. Symptoms manifest in infancy, including frequent seizures, hypotonia (low muscle tone), developmental delay, failure to thrive, skeletal abnormalities, facial dysmorphism (abnormal difference in structure), respiratory and intestinal problems, and brain, heart, kidney, and eye abnormalities.

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Also known as Polypeptide N-Acetylgalactosaminyltransferase 2 Deficiency

A very rare, multisystemic, inherited condition caused by an abnormal enzyme which disrupts O-glycosylation. Symptoms manifest during infancy and childhood, including global developmental delay, intellectual disability, behavioral abnormalities, epilepsy, insomnia, stunted growth, facial dysmorphism (abnormal difference in structure), decreased HDL-cholesterol, and white matter brain lesions.

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Also known as Congenital Disorder of Glycosylation Type IIu; Rafiq Syndrome; MAN1B1 Deficiency; Intellectual Disability-Truncal Obesity Syndrome

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Also known as MAN2B2 Deficiency

MAN2B2 Congenital Disorder of Glycosylation A rare, inherited condition caused by abnormal proteins disrupting glycosylation. In the single reported case, symptoms manifested in infancy, including recurrent infections, vasculitis, arthritis, thrombotic stroke, chronic diarrhea, cardiac and eye abnormalities, facial dysmorphism (abnormal difference in structure), speech and developmental delays, hepatomegaly (enlarged liver), and pectus carinatum (protruding breastbone).

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Also known as Congenital Disorder of Glycosylation Type Ib

A rare, inherited condition caused by abnormal proteins disrupting N-linked glycosylation and mainly affecting the liver and intestinal system. Symptoms manifest during infancy, including cyclic vomiting, failure to thrive, hypoglycemia, hypoalbuminemia, coagulopathy, liver fibrosis (formation of scar tissue) or steatosis (buildup of fat), hepatomegaly (enlarged liver), and, rarely, portal hypertension.

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Also known as NGLY1 Congenital Disorder of Deglycosylation

A rare, inherited condition caused by an abnormal enzyme disrupting N-linked deglycosylation. Symptoms manifest during infancy, including hypotonia (low muscle tone), seizures, liver disease, eye problems, failure to thrive, hyperkinetic movements, motor and speech delays, peripheral neuropathy, apnea, hypohydrosis, hearing loss, hypermobile joints, and scoliosis.

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Also known as Post-GPI Attachment to Proteins Phospholipase 3 deficiency or Hyperphosphatasia with mental retardation syndrome 4

PGAP3-CDG is a rare genetic disease grouped with other disorders disrupting Glycosylphosphatidylinositol (GPI-) anchor synthesis. It is characterized by intellectual disability and increased levels of an enzyme called alkaline phosphatase (AP) in the blood (hyperphosphatasia).

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Also known as Congenital Disorder of Glycosylation Type It

A rare, multisystemic, inherited condition caused by an abnormal protein disrupting glycosylation. Symptoms manifest in infancy, including hypoglycemic seizures, hypotonia (low muscle tone), liver disease, motor developmental delay, failure to thrive, a cleft palate, cardiomyopathy, myopathy, muscle atrophy, rhabdomyolysis, exercise intolerance, and blood clots.

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Also known as Phosphatidylinositol-Glycan Class A Protein Deficiency; Multiple Congenital Anomalies-Hypotonia-Seizures Syndrome 2

A rare, X-linked, glycosylphosphatidylinositol anchor defect disorder, caused by an abnormal enzyme disrupting glycosylation. Symptoms include global developmental delay, seizures, hypo/hypertonia, dystonia, cortical visual impairment, slow gastrointestinal motility, delayed myelination, and problems with sleep, respiration, and swallowing.

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Also known as Multiple Congenital Anomalies-Hypotonia-Seizures Syndrome; it belongs to a group of disorders called Glycosylphosphatidylinositol (GPI-) anchor defects

PIGT-CDG is a very rare inherited condition that affects multiple parts of the body and causes multiple congenital anomalies. Affected individuals typically develop signs and symptoms of the condition during infancy.

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Also known as Phosphatidylinositol-glycan Class T Protein Deficiency or Multiple Congenital Anomalies-Hypotonia-Seizures Syndrome 3. It belongs to a group of disorders called Glycosylphosphatidylinositol (GPI-) anchor defects.

PIGT-CDG is a very rare inherited condition that affects multiple parts of the body and causes multiple congenital anomalies. Affected individuals typically develop signs and symptoms of the condition during infancy.

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Also known as congenital disorder of glycosylation type Ia

PMM2-CDG is an inherited condition that affects many parts of the body. Individuals with PMM2-CDG typically develop signs and symptoms of the condition during infancy.

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Also known as Congenital Disorder of Glycosylation Type IIm

A rare, X-linked dominant, inherited condition caused by an abnormal enzyme disrupting glycosylation. Symptoms manifest in infancy, including seizures, hypotonia (low muscle tone), global developmental delay, failure to thrive, splenomegaly (enlarged spleen), hearing and vision loss, ataxia (impaired balance or coordination), hypertrophic cardiomyopathy, coarse facial features, short limbs, scoliosis, and thrombocytopenia (low blood platelet count).

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Also known as Leukocyte Adhesion Deficiency Type II (formerly known as CDG IIc)

A rare, inherited condition primarily affecting the immune, endocrine, and nervous systems. It is caused by an abnormal transport protein that disrupts glycosylation. Symptoms manifest in infancy or childhood, including recurrent bacterial infections, the Bombay blood type, short stature, developmental delay, cognitive impairment, behavioral problems, seizures, and hypotonia (low muscle tone).

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Also known as SLC39A8 Deficiency; Carbohydrate Deficient Glycoprotein Syndrome Type IIn; Congenital Disorder of Glycosylation Type 2n; CDG Syndrome Type Iin

A rare, multisystemic, inherited condition, caused by an abnormal transport protein, leading to manganese deficiency and disruption of glycosylation. Symptoms manifest in infancy, including global and psychomotor developmental delays, cognitive impairment, seizures, muscle weakness, hypotonia (low muscle tone), dwarfism, hearing and vision loss, recurrent infections, and skeletal abnormalities.

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Also known as Congenital Disorder of Glycosylation Type Iq; SRD5A3 deficiency

A rare, multisystemic, inherited condition affecting mainly the neurological system, caused by an abnormal enzyme disrupting N-linked glycosylation. Symptoms manifest in infancy, including balance and coordination problems (ataxia), hypotonia (low muscle tone), facial dysmorphism (abnormal difference in body structure), kyphosis (outward curvature of the spine), joint hypermobility, and cardiac, eye, and dermatological problems.

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Also known as SSR4-deficiency; Deficiency of Signal Sequence Receptor Protein 4; Congenital Disorder of Glycosylation Iy

A rare, X-linked recessive, multisystemic, inherited condition, caused by an abnormal transport protein disrupting N-linked glycosylation. Symptoms manifest in infancy, including global developmental delay, intellectual disability, seizures, hypotonia (low muscle tone), failure to thrive, facial dysmorphism (abnormal difference in structure), connective tissue symptoms, and skeletal, gastrointestinal, and eye abnormalities.

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Also known as congenital disorder of glycosylation Iw

STT3A-CDG is an extremely rare inherited condition that affects multiple parts of the body. It can be inherited in an autosomal recessive pattern (both copies of the genes have changes for symptoms to develop) or an autosomal dominant pattern (only one copy of the gene has a change in order for symptoms to occur) depending on the specific change in the gene STT3.

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Also known as VMA21 deficiency with liver disease

VMA21-CDG is an extremely rare inherited condition that has only very recently been reported to cause CDG. There are only three individuals with VMA21-CDG that have been published in the medical literature so far.

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