Overview
Disorders of cobalamin (vitamin B12) metabolism and transport are a group of rare inherited conditions where the body cannot properly process or move vitamin B12. Vitamin B12 is essential for making red blood cells, keeping nerves healthy, and building DNA. When the body cannot use B12 correctly, it leads to a buildup of harmful substances — mainly homocysteine and methylmalonic acid — that damage the brain, nerves, blood, and other organs. There are many different subtypes of this disorder, often named with letters like cblA, cblB, cblC, cblD, cblE, cblF, cblG, cblJ, and others. Each subtype is caused by a change (mutation) in a different gene that controls how B12 is absorbed, transported, or converted into its active forms inside cells. The most common subtype is cblC, which typically causes problems in infancy or early childhood. Symptoms vary widely depending on the subtype but often include developmental delays, intellectual disability, anemia, feeding difficulties, and neurological problems. Some forms also affect the eyes and kidneys. Treatment usually involves high-dose hydroxocobalamin (a form of B12) injections, sometimes combined with other supplements like betaine or folate. Early diagnosis and treatment can significantly improve outcomes, though some neurological damage may be permanent if treatment is delayed.
Key symptoms:
Developmental delays or intellectual disabilityFeeding difficulties and poor weight gain in infancyAnemia (low red blood cell count causing tiredness and paleness)SeizuresMuscle weakness or low muscle toneVision problems, including damage to the retinaKidney disease (in some subtypes)Abnormal blood clotting or blood vessel problemsBehavioral or psychiatric problemsNumbness or tingling in hands and feetDifficulty walking or movement problemsElevated homocysteine levels in blood and urineElevated methylmalonic acid levels in blood and urine
Autosomal recessive
Passed on when both parents carry the same gene change; often skips generations
Variable
Can begin at different ages, from infancy through adulthood
Treatments
No FDA-approved treatments are currently listed for Disorder of cobalamin metabolism and transport.
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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
No travel grants are currently matched to Disorder of cobalamin metabolism and transport.
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Caregiver Resources
NORD Caregiver Resources
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Mental Health Support
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Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Questions for your doctor
Bring these to your next appointment
- Q1.Which specific subtype of cobalamin disorder does my child or I have, and what does that mean for treatment and prognosis?,How often do we need hydroxocobalamin injections, and can we learn to give them at home?,What blood and urine tests should be monitored regularly, and how often?,Are there any dietary changes or supplements we should start right away?,What signs of a metabolic crisis should prompt us to go to the emergency room?,Should other family members be tested for this condition?,Are there any clinical trials or new treatments we should know about?
Common questions about Disorder of cobalamin metabolism and transport
What is Disorder of cobalamin metabolism and transport?
Disorders of cobalamin (vitamin B12) metabolism and transport are a group of rare inherited conditions where the body cannot properly process or move vitamin B12. Vitamin B12 is essential for making red blood cells, keeping nerves healthy, and building DNA. When the body cannot use B12 correctly, it leads to a buildup of harmful substances — mainly homocysteine and methylmalonic acid — that damage the brain, nerves, blood, and other organs. There are many different subtypes of this disorder, often named with letters like cblA, cblB, cblC, cblD, cblE, cblF, cblG, cblJ, and others. Each subtype
How is Disorder of cobalamin metabolism and transport inherited?
Disorder of cobalamin metabolism and transport follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.