Overview
Hypermethioninemia encephalopathy due to adenosine kinase deficiency (also called ADK deficiency) is an extremely rare inherited metabolic disorder. It is caused by mutations in the ADK gene, which provides instructions for making an enzyme called adenosine kinase. This enzyme plays a key role in processing a molecule called adenosine and is also important for a chemical process called methylation, which the body uses to regulate many functions including brain development. When adenosine kinase does not work properly, a substance called methionine builds up in the blood (hypermethioninemia), and a related compound called S-adenosylhomocysteine also accumulates. This disrupts normal methylation throughout the body, particularly affecting the brain and liver. Children with this condition typically show signs in the newborn period or early infancy, including developmental delay, intellectual disability, seizures, liver problems, and distinctive facial features. Some children may also have low muscle tone and feeding difficulties. There is currently no cure for this condition. Treatment is mainly supportive and focuses on managing symptoms such as seizures, supporting development through therapies, and monitoring liver function. A low-methionine diet may be tried to help reduce the buildup of methionine, though its effectiveness varies. Early diagnosis and a team of specialists are important to provide the best possible care and quality of life.
Key symptoms:
Developmental delayIntellectual disabilitySeizuresLiver problems or enlarged liverLow muscle tone (floppiness)Feeding difficulties in infancyDistinctive facial featuresSpeech delay or absence of speechMovement problemsElevated methionine levels in the bloodBehavioral difficultiesPoor weight gain or failure to thriveSleep disturbances
Autosomal recessive
Passed on when both parents carry the same gene change; often skips generations
Neonatal
Begins at or shortly after birth (first 4 weeks)
Treatments
No FDA-approved treatments are currently listed for Hypermethioninemia encephalopathy due to adenosine kinase deficiency.
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Specialists
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Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
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Caregiver Resources
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Questions for your doctor
Bring these to your next appointment
- Q1.What is the severity of my child's ADK deficiency, and what symptoms should I expect over time?,Should my child follow a low-methionine diet, and how effective is it likely to be?,What seizure medications are best for my child, and what side effects should I watch for?,How often should my child's liver function be checked?,Are there any clinical trials or emerging treatments we should know about?,What developmental therapies do you recommend, and how often should they occur?,Should other family members be tested for carrier status, and what does this mean for future pregnancies?
Common questions about Hypermethioninemia encephalopathy due to adenosine kinase deficiency
What is Hypermethioninemia encephalopathy due to adenosine kinase deficiency?
Hypermethioninemia encephalopathy due to adenosine kinase deficiency (also called ADK deficiency) is an extremely rare inherited metabolic disorder. It is caused by mutations in the ADK gene, which provides instructions for making an enzyme called adenosine kinase. This enzyme plays a key role in processing a molecule called adenosine and is also important for a chemical process called methylation, which the body uses to regulate many functions including brain development. When adenosine kinase does not work properly, a substance called methionine builds up in the blood (hypermethioninemia),
How is Hypermethioninemia encephalopathy due to adenosine kinase deficiency inherited?
Hypermethioninemia encephalopathy due to adenosine kinase deficiency follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Hypermethioninemia encephalopathy due to adenosine kinase deficiency typically begin?
Typical onset of Hypermethioninemia encephalopathy due to adenosine kinase deficiency is neonatal. Age of onset can vary across affected individuals.