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Disease Information

Summary
Glycine encephalopathy is an inherited metabolic disease characterized by abnormally high levels of an amino acid called glycine. Glycine is a chemical messenger that transmits signals in the brain. According to the symptoms the disease onset, Glycine encephalopathy may be divided in 4 forms. Classical neonatal form (most common): Symptoms start within a few days of life and may include poor feeding, lack of energy (lethargy), weak muscle tone (hypotonia), hiccups, breathing problems, seizures, hiccups, and coma. Transient form: Symptoms are similar to the classic form, but glycine levels decrease and the symptoms may improve within time. Glycine encephalopathy is caused by changes in the AMT, GLDC or GCSH genes which result in a deficiency of the enzyme that break-up the glycine. Diagnosis is based in the symptoms, the high glycine levels and the enzyme deficiency, as well as genetic testing. Inheritance is autosomal recessive.
Summary
Glycine encephalopathy is an inherited metabolic disease characterized by abnormally high levels of an amino acid called glycine. Glycine is a chemical messenger that transmits signals in the brain. According to the symptoms the disease onset, Glycine encephalopathy may be divided in 4 forms. Classical neonatal form (most common): Symptoms start within a few days of life and may include poor feeding, lack of energy (lethargy), weak muscle tone (hypotonia), hiccups, breathing problems, seizures, hiccups, and coma. Transient form: Symptoms are similar to the classic form, but glycine levels decrease and the symptoms may improve within time. Glycine encephalopathy is caused by changes in the AMT, GLDC or GCSH genes which result in a deficiency of the enzyme that break-up the glycine. Diagnosis is based in the symptoms, the high glycine levels and the enzyme deficiency, as well as genetic testing. Inheritance is autosomal recessive.
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Resource(s) for Medical Professionals and Scientists on This Disease:
  • GeneReview  provides clinical information on genetic diseases, including diagnosis, treatment, and genetic counseling.

About Glycine encephalopathy

Many rare diseases have limited information. Currently, GARD aims to provide the following information for this disease:

  • Population Estimate:Fewer than 50,000 people in the U.S. have thisdisease.
  • Symptoms:May start to appear as a Newborn and as an Infant.
  • Cause:This disease has more than one possible cause.
  • Organizations:Patient organizations dedicated to this rare disease are available on GARD, or you may contact a GARD Information Specialist for additional information.
  • Newborn Screening:This disease may be detected through newborn screening tests performed soon afterbirth.
  • Categories:GeneticdiseasesNeurologicaldiseasesInherited Metabolicdiseases

Causes

What Causes This Disease?

Genetic Mutations

Glycine encephalopathy is caused by genetic mutations, also known as pathogenic variants. Genetic mutations can be hereditary, when parents pass them down to their children, or they may occur randomly when cells are dividing. Genetic mutations may also result from contracted viruses, environmental factors, such as UV radiation from sunlight exposure, or a combination of any of these. Learn more about genetic diseases from the National Library of Medicine (NLM).

If you suspect you may have this disease, you may want to start collecting your family health history. Information such as other family members who have had similar symptoms, when their/your symptoms first appeared, or exposures to any potential disease-causing environmental factors should be discussed with your medical team. This tool from the Surgeon General can help you collect your family health history.

Can This Disease Be Passed Down From Parent to Child?

Yes. It is possible for a biological parent to pass down genetic mutations that cause or increase the chances of getting this disease to their child. This is known as inheritance. Knowing whether other family members have previously had this disease, also known as family health history, can be very important information for your medical team. This tool from the Surgeon General can help you collect your family health history.

There are multiple ways, or patterns, a disease can be inherited depending on the gene(s) involved. Based on GARD's current data, this disease can be inherited in the following pattern(s):

Autosomal Recessive

Autosomal means the gene involved is located on one of the numbered chromosomes. Recessive means that a child must inherit two copies of the mutated gene, one from each biological parent, to be affected by the disease. A carrier is a person who only has one copy of the genetic mutation. A carrier usually doesn't show any symptoms of the disease.

If both biological parents are carriers, there is a 25% their child inherits both copies of the mutated gene and is affected by the disease. Additionally, there is a 50% chance their child inherits only one copy of the mutated gene and is a carrier.

Learn more about inheritance patterns from the National Library of Medicine (NLM).

When Do Symptoms of Glycine encephalopathy Begin?

Symptoms of this disease may start to appear as a Newborn and as an Infant.

The age symptoms may begin to appear differs between diseases. Symptoms may begin in a single age range, or during several age ranges. The symptoms of some diseases may begin at any age. Knowing when symptoms may have appeared can help medical providers find the correct diagnosis.
Prenatal
Before Birth
Newborn Selected
Birth-4 weeks
Infant Selected
1-23 months
Child
2-11 years
Adolescent
12-18 years
Adult
19-65 years
Older Adult
65+ years
Symptoms may start to appear as a Newborn and as an Infant.
This information comes from Orphanet

Symptoms

The types of symptoms experienced, and their intensity, may vary among people with this disease. Your experience may be different from others. Consult your health care team for more information.

The following describes the symptom(s) associated with this disease along with the corresponding body system(s), description, synonyms, and frequency (Note: Not all possible symptoms may be listed):
Nervous System Nervous System

8 Symptoms

8 Symptoms

8 Symptoms

Nervous System

The nervous system is made up of the brain, spinal cord, and nerves. Common symptoms of problems in the nervous system include trouble moving, speaking, swallowing, breathing, or learning. Problems with memory, senses, or mood may also occur. Nervous system diseases are usually diagnosed and treated by neurologists.
Medical Term

Hypoplasia of the corpus callosum

Frequency
Uncommon
Very frequent
Very frequent
Always
Description
Underdevelopment of the corpus callosum.
Synonym
Corpus callosum hypoplasia; Hypoplasia of corpus callosum; Hypoplastic corpus callosum; Underdevelopment of part of brain called corpus callosum
Open detail view
8 Symptoms
This information comes from the Human Phenotype Ontology (HPO)

Diagnostic Journey

On average, it takes more than six years to receive an accurate rare disease diagnosis. Many primary care providers (PCPs) may not be familiar with rare diseases, and you may need to see multiple specialists to reach the correct diagnosis. However, advocating for yourself with your healthcare team may help speed your time to diagnosis. To combat common challenges, be prepared:

  • Find disease-specific information to discuss with your healthcare providers.
  • Ask for diagnostic tests.
  • Request referrals to specialists.

Knowing where to start your diagnostic journey and how to navigate the next steps are critical to speeding your time to diagnosis

Your Diagnostic Team

How can a diagnostic team help?

Establishing care with a dedicated primary care provider (PCP) is an important early step in your rare disease journey. A PCP can help improve care and shorten the time to diagnosis by providing referrals to the appropriate specialists. These specialists, with advanced training in different body systems or types of diseases, can offer the specialized diagnostic procedures you need.

Use this tool by Medicare to find a PCP in your area by inputting your location and keyword "Primary Care Provider."

A PCP that specializes in the care of children is called a pediatrician. Use this tool by the American Academy of Pediatrics to find a pediatrician in your area by inputting your location.
Diagnostic teams for Glycine encephalopathy may include:
 

Multidisciplinary Care Centers

Is it time to find a multidisciplinary care center?

If you've visited your PCP, met with specialists, and undergone the recommended tests, but still do not have a confirmed diagnosis, it may be time to visit a multidisciplinary care center. Multidisciplinary care centers are usually teaching, university, or research hospitals that have teams of medical experts and specialists working together in the same location. This means a wide range of diagnostic tests and clinical knowledge are available at one facility, which can help increase communication and collaboration among your care team. The additional resources often available at multidisciplinary centers may help speed the time to diagnosis for rare diseases.

Use this tool to find hospitals that may partner with medical schools and programs in your area.

Some multidisciplinary care centers focus on the care and treatment of children. Use this tool to find children's multidisciplinary care centers by searching for university or research hospitals in your area.

Multidisciplinary Care Centers

Is it time to find a multidisciplinary care center?

If you've visited your PCP, met with specialists, and undergone the recommended tests, but still do not have a confirmed diagnosis, it may be time to visit a multidisciplinary care center. Multidisciplinary care centers are usually teaching, university, or research hospitals that have teams of medical experts and specialists working together in the same location. This means a wide range of diagnostic tests and clinical knowledge are available at one facility, which can help increase communication and collaboration among your care team. The additional resources often available at multidisciplinary centers may help speed the time to diagnosis for rare diseases.

Use this tool to find hospitals that may partner with medical schools and programs in your area.

Some multidisciplinary care centers focus on the care and treatment of children. Use this tool to find children's multidisciplinary care centers by searching for university or research hospitals in your area.

Rare Disease Experts

How can you find a rare disease expert?

If a diagnosis remains unknown despite extensive efforts by your PCP and specialists, it can be challenging to know what kind of expert you may need or where to find one. A rare disease expert is a care provider that has knowledge or training on specific disease(s), but there may only be a few experts in your state, region, or country. Rare disease experts may work at large research or teaching hospitals. In complex cases, coordinating with a network of experts can help your care provider find the right diagnosis. 
Contact a GARD Information Specialist for help finding an expert.

You can ask your care providers for help finding an expert or use directory tools to search for experts near you. The National Organization for Rare Disorders (NORD) maintains a list of rare disease centers with experts that work together to find treatments and cures for a broad range of rare diseases. Search NORD's Center Directory to find experts near you.

Rare Disease Experts

How can you find a rare disease expert?

If a diagnosis remains unknown despite extensive efforts by your PCP and specialists, it can be challenging to know what kind of expert you may need or where to find one. A rare disease expert is a care provider that has knowledge or training on specific disease(s), but there may only be a few experts in your state, region, or country. Rare disease experts may work at large research or teaching hospitals. In complex cases, coordinating with a network of experts can help your care provider find the right diagnosis. 
Contact a GARD Information Specialist for help finding an expert.

You can ask your care providers for help finding an expert or use directory tools to search for experts near you. The National Organization for Rare Disorders (NORD) maintains a list of rare disease centers with experts that work together to find treatments and cures for a broad range of rare diseases. Search NORD's Center Directory to find experts near you.
 

Find Your Community

How can patient organizations help?

Patient organizations can help patients and families connect. They build public awareness of the disease and are a driving force behind research to improve patients' lives. They may offer online and in-person resources to help people live well with their disease. Many collaborate with medical experts and researchers.

Services of patient organizations differ, but may include:

  • Ways to connect to others and share personal stories
  • Easy-to-read information
  • Up-to-date treatment and research information
  • Patient registries
  • Lists of specialists or specialty centers
  • Financial aid and travel resources


Please note: GARD provides organizations for informational purposes only and not as an endorsement of their services. Contact a GARD Information Specialist for more information on organizations that may be dedicated to this disease. Please contact an organization directly if you have questions about the information or resources it provides.


View GARD's criteria for including patient organizations, which can be found under the FAQs on our About GARD page. Request an update or to have your organization added to GARD. 

Patient Organizations

5 Organizations

Organization Name

Who They Serve

Helpful Links

Country

NKH International Family Network
People With

Glycine encephalopathy

Helpful Links
Country

United States

EveryLife Foundation for Rare Diseases
People With

Rare Diseases

Helpful Links
Country

United States

Genetic Alliance
People With

Rare Diseases

Helpful Links
Country

United States

Global Genes
People With

Rare Diseases

Helpful Links
Country

United States

National Organization for Rare Disorders
People With

Rare Diseases

Helpful Links
Country

United States

Participate in Research

Clinical studies are a part of clinical research and play an important role in medical advances for rare diseases. Through clinical studies, researchers may ultimately uncover better ways to treat, prevent, diagnose, and understand human diseases.

What Are Clinical Studies?

Clinical studies are medical research involving people as participants. There are two main types of clinical studies:

  1. Clinical trials determine if a new test or treatment for a disease is effective and safe by comparing groups receiving different tests/treatments.
  2. Observational studies involve recording changes over time among a specific group of people in their natural settings.

Learn more about clinical trials from this National Institutes of Health webpage.

Why Participate in Clinical Studies?

People participate in clinical trials for many reasons. People with a disease may participate to receive the newest possible treatment and additional care from clinical study staff as well as to help others living with the same or a similar disease. Healthy volunteers may participate to help others and to contribute to moving science forward.

To find the right clinical study we recommend you consult your doctors, other trusted medical professionals, and patient organizations. Additionally, you can use ClinicalTrials.gov to search for clinical studies by disease, terms, or location.

What if There Are No Available Clinical Studies?

ResearchMatch helps connect people interested in research studies  with researchers from top medical centers across the United States. Anyone from the U.S. can register with this free program funded by NIH. Researchers from participating institutions use the database to search for and invite patients or healthy volunteers who meet their study criteria to participate.

Join the All of Us Research Program!

The All of Us Research Program is inviting 1 million people from all backgrounds across the U.S. to help build one of the most diverse health databases in history. Researchers will use the data to learn how our biology, lifestyle, and environment affect health. This may one day help them find ways to treat and prevent diseases.

What Are Clinical Studies?

Clinical studies are medical research involving people as participants. There are two main types of clinical studies:

  1. Clinical trials determine if a new test or treatment for a disease is effective and safe by comparing groups receiving different tests/treatments.
  2. Observational studies involve recording changes over time among a specific group of people in their natural settings.

Learn more about clinical trials from this National Institutes of Health webpage.

Read More

Why Participate in Clinical Studies?

People participate in clinical trials for many reasons. People with a disease may participate to receive the newest possible treatment and additional care from clinical study staff as well as to help others living with the same or a similar disease. Healthy volunteers may participate to help others and to contribute to moving science forward.

To find the right clinical study we recommend you consult your doctors, other trusted medical professionals, and patient organizations. Additionally, you can use ClinicalTrials.gov to search for clinical studies by disease, terms, or location.
Read More

What if There Are No Available Clinical Studies?

ResearchMatch helps connect people interested in research studies  with researchers from top medical centers across the United States. Anyone from the U.S. can register with this free program funded by NIH. Researchers from participating institutions use the database to search for and invite patients or healthy volunteers who meet their study criteria to participate.

Join the All of Us Research Program!

The All of Us Research Program is inviting 1 million people from all backgrounds across the U.S. to help build one of the most diverse health databases in history. Researchers will use the data to learn how our biology, lifestyle, and environment affect health. This may one day help them find ways to treat and prevent diseases.

ClinicalTrials.gov, an affiliate of NIH, provides current information on clinical research studies in the United States and abroad. Talk to a trusted doctor before choosing to participate in any clinical study. We recommend checking this site often and searching for studies with related terms/synonyms to improve results.
Search ClinicalTrials.gov for this disease.
Contact a GARD Information Specialist if you need help finding more information on this rare disease or available clinical studies. Please note that GARD cannot enroll individuals in clinical studies.
1-888-205-2311
Available Monday through Friday 12 p.m. to 6 p.m. Eastern Time
(Except: Federal Holidays)
Contact GARD
Use the contact form to send your questions to a GARD Information Specialist.

Please allow 2 to 10 business days for us to respond.
ClinicalTrials.gov, an affiliate of NIH, provides current information on clinical research studies in the United States and abroad. Talk to a trusted doctor before choosing to participate in any clinical study. We recommend checking this site often and searching for studies with related terms/synonyms to improve results.
Search ClinicalTrials.gov for this disease.
Contact a GARD Information Specialist if you need help finding more information on this rare disease or available clinical studies. Please note that GARD cannot enroll individuals in clinical studies.
1-888-205-2311
Available Monday through Friday 12 p.m. to 6 p.m. Eastern Time
(Except: Federal Holidays)
Contact GARD
Use the contact form to send your questions to a GARD Information Specialist.

Please allow 2 to 10 business days for us to respond.

Last Updated: May 2025