Overview
Sulfite oxidase deficiency due to molybdenum cofactor deficiency type B (also called MoCD type B or MOCS2 deficiency) is a very rare and serious inherited metabolic disorder. In this condition, the body cannot properly make a small but essential molecule called the molybdenum cofactor. This cofactor is needed for several important enzymes to work, including sulfite oxidase, which breaks down sulfur-containing amino acids from the protein in our diet. When sulfite oxidase does not work, toxic sulfite builds up in the body and causes severe damage, especially to the brain. Babies with this condition typically appear normal at birth but quickly develop serious neurological problems within the first days to weeks of life. These include seizures that are very difficult to control, feeding difficulties, abnormal muscle tone, and progressive brain damage. Brain imaging often shows widespread injury and swelling. The buildup of toxic substances leads to intellectual disability, movement problems, and often a characteristic lens dislocation in the eyes similar to what is seen in isolated sulfite oxidase deficiency. Unfortunately, the treatment landscape for MoCD type B remains very limited. Unlike MoCD type A, for which a specific replacement therapy (fosdenopterin, brand name Nulibek) has been developed, there is currently no equivalent targeted treatment available for type B. Management is mainly supportive, focusing on controlling seizures, providing nutritional support, and managing complications. Research is ongoing to find better therapies, but the prognosis remains poor for most affected children.
Also known as:
Key symptoms:
Seizures that start in the first days of life and are hard to controlFeeding difficulties in infancyAbnormal muscle tone (either too stiff or too floppy)Severe intellectual disabilityDevelopmental delay or loss of developmental milestonesInvoluntary abnormal movementsLens dislocation in the eyesSmall head size (microcephaly)Brain damage visible on MRIPoor growth and failure to thriveEpisodes of vomitingIrritability and excessive cryingBreathing difficulties
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 Sulfite oxidase deficiency due to molybdenum cofactor deficiency type B.
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Specialists
View all specialists →No specialists are currently listed for Sulfite oxidase deficiency due to molybdenum cofactor deficiency type B.
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 Sulfite oxidase deficiency due to molybdenum cofactor deficiency type B.
Community
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Caregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
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.What is the specific genetic mutation found in my child, and does it affect treatment options?,Are there any clinical trials or experimental treatments available for MoCD type B?,What is the best approach to managing my child's seizures, and what should I do during a seizure emergency?,Should my child be on a special diet, and will it help?,How often should my child have brain imaging and eye exams?,What supportive therapies (physical therapy, occupational therapy) would benefit my child?,Should other family members be tested as carriers, and what are the chances for future pregnancies?
Common questions about Sulfite oxidase deficiency due to molybdenum cofactor deficiency type B
What is Sulfite oxidase deficiency due to molybdenum cofactor deficiency type B?
Sulfite oxidase deficiency due to molybdenum cofactor deficiency type B (also called MoCD type B or MOCS2 deficiency) is a very rare and serious inherited metabolic disorder. In this condition, the body cannot properly make a small but essential molecule called the molybdenum cofactor. This cofactor is needed for several important enzymes to work, including sulfite oxidase, which breaks down sulfur-containing amino acids from the protein in our diet. When sulfite oxidase does not work, toxic sulfite builds up in the body and causes severe damage, especially to the brain. Babies with this cond
How is Sulfite oxidase deficiency due to molybdenum cofactor deficiency type B inherited?
Sulfite oxidase deficiency due to molybdenum cofactor deficiency type B follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Sulfite oxidase deficiency due to molybdenum cofactor deficiency type B typically begin?
Typical onset of Sulfite oxidase deficiency due to molybdenum cofactor deficiency type B is neonatal. Age of onset can vary across affected individuals.