Overview
Methylmalonic acidemia with homocystinuria, type cblJ (also called combined methylmalonic acidemia and homocystinuria, cblJ type) is an extremely rare inherited metabolic disorder. It belongs to a group of conditions caused by problems in how the body processes vitamin B12 (cobalamin). In this specific type, a defect in the ABCD4 gene disrupts the transport of vitamin B12 inside cells, which means the body cannot properly use this vitamin for two important chemical reactions. As a result, harmful substances called methylmalonic acid and homocysteine build up in the blood and urine. Symptoms can appear in infancy or early childhood and may include feeding difficulties, poor growth (failure to thrive), low muscle tone, developmental delays, and blood abnormalities such as megaloblastic anemia (a type of anemia where red blood cells are abnormally large). Some affected individuals may also experience neurological problems, including seizures and intellectual disability. The severity of symptoms can vary from person to person. Treatment typically involves supplementation with hydroxocobalamin (a form of vitamin B12), which can help reduce the buildup of toxic substances in the body. Betaine may also be used to help lower homocysteine levels. Early diagnosis and prompt treatment are important because they can significantly improve outcomes. However, because this condition is so rare, long-term data on outcomes are still limited, and management often requires a team of specialists working together.
Also known as:
Key symptoms:
Feeding difficulties in infancyPoor growth or failure to thriveLow muscle tone (floppiness)Developmental delaysIntellectual disabilityMegaloblastic anemia (large, abnormal red blood cells)Low blood cell countsSeizuresLethargy or excessive sleepinessElevated methylmalonic acid in blood and urineElevated homocysteine in bloodHeart defects in some casesSkin changes or rashesVision problems
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 Methylmalonic acidemia with homocystinuria, type cblJ.
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Specialists
View all specialists →No specialists are currently listed for Methylmalonic acidemia with homocystinuria, type cblJ.
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 Methylmalonic acidemia with homocystinuria, type cblJ.
Community
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Caregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
Mental Health Support
Rare disease caregiving can be isolating. Connect with counseling and peer support.
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.How severe is my child's condition based on current lab results?,How often will hydroxocobalamin injections be needed, and can they be given at home?,What signs of a metabolic crisis should I watch for, and what should I do in an emergency?,Will my child need dietary restrictions, and should we see a metabolic dietitian?,What developmental therapies should we start, and how soon?,How often will blood tests and follow-up visits be needed?,Are there any clinical trials or new treatments being studied for this condition?
Common questions about Methylmalonic acidemia with homocystinuria, type cblJ
What is Methylmalonic acidemia with homocystinuria, type cblJ?
Methylmalonic acidemia with homocystinuria, type cblJ (also called combined methylmalonic acidemia and homocystinuria, cblJ type) is an extremely rare inherited metabolic disorder. It belongs to a group of conditions caused by problems in how the body processes vitamin B12 (cobalamin). In this specific type, a defect in the ABCD4 gene disrupts the transport of vitamin B12 inside cells, which means the body cannot properly use this vitamin for two important chemical reactions. As a result, harmful substances called methylmalonic acid and homocysteine build up in the blood and urine. Symptoms c
How is Methylmalonic acidemia with homocystinuria, type cblJ inherited?
Methylmalonic acidemia with homocystinuria, type cblJ follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.