Cobalamin C Disease (cblC)
What is Cobalamin C Disease (cblC)?
Cobalamin C Disease is a rare inherited disorder that affects how your body processes vitamin B12. Your body needs vitamin B12 to make energy, build proteins, and keep your nervous system healthy. In cblC disease, a genetic mutation prevents your cells from converting vitamin B12 into two essential forms that your body can actually use.
When this conversion fails, two harmful substances build up in your blood. Homocysteine and methylmalonic acid accumulate to dangerous levels. These substances can damage your brain, eyes, kidneys, and blood cells. The condition is present from birth and is one of the most common types of inherited vitamin B12 processing disorders.
Most cases appear in infancy, but some people develop symptoms later in childhood or even adulthood. Early diagnosis and treatment can prevent serious complications. The condition requires lifelong management with special forms of vitamin B12 and other supplements that bypass the faulty metabolic pathway.
Symptoms
- Poor feeding and failure to gain weight in infants
- Vomiting and decreased appetite
- Extreme tiredness and low energy levels
- Developmental delays or loss of milestones
- Weak muscle tone or poor coordination
- Vision problems including light sensitivity and reduced sight
- Pale skin from anemia or low red blood cell count
- Seizures or abnormal movements
- Intellectual disability if left untreated
- Blood clotting problems or easy bruising
Symptoms typically appear within the first few months of life. However, some people with milder forms may not show signs until later childhood or adulthood. The severity varies widely depending on how much enzyme function remains.
Concerned about Cobalamin C Disease (cblC)? Check your levels.
Screen for 1,200+ health conditions
Causes and risk factors
Cobalamin C Disease is caused by mutations in the MMACHC gene. This gene provides instructions for making an enzyme that processes vitamin B12. You inherit the condition when you receive one faulty copy of the gene from each parent. Parents who carry one mutated copy are usually healthy and often do not know they carry the gene.
The condition occurs in about 1 in 100,000 births worldwide, making it extremely rare. Certain populations have higher rates due to founder effects. Risk factors include having parents who are related by blood, being of Northern European or Middle Eastern descent, or having a family history of the condition. Newborn screening programs in many states now test for this disorder, allowing for early detection before symptoms develop.
How it's diagnosed
Cobalamin C Disease is diagnosed through a combination of blood tests, urine tests, and genetic testing. Blood tests measuring homocysteine levels are essential for detecting the condition. Elevated homocysteine along with high methylmalonic acid in blood and urine strongly suggests cblC disease. Your doctor may also check for anemia, low platelet counts, and abnormal red blood cell size.
Rite Aid offers homocysteine testing as an add-on to help screen for vitamin B12 metabolism disorders. If results are abnormal, your doctor will order specialized confirmatory tests including genetic testing to identify the specific MMACHC gene mutation. Brain imaging and eye exams may also be needed to assess organ damage. Early diagnosis through newborn screening or blood testing allows treatment to start before irreversible damage occurs.
Treatment options
- Intramuscular injections of hydroxocobalamin, a special form of vitamin B12
- Oral betaine supplements to lower homocysteine levels
- Folic acid or folinic acid supplements to support metabolism
- Carnitine supplementation to help clear toxic byproducts
- Low-protein diet to reduce methylmalonic acid production
- Regular monitoring of blood homocysteine and methylmalonic acid levels
- Physical therapy to address developmental delays or muscle weakness
- Vision care and monitoring with an ophthalmologist
- Treatment of anemia with additional supplements if needed
- Genetic counseling for families planning future pregnancies
Need testing for Cobalamin C Disease (cblC)? Add it to your panel.
- Simple blood draw at your nearest lab
- Results in days, not weeks
- Share results with your doctor
Frequently asked questions
Life expectancy varies greatly depending on when treatment begins and how severe the condition is. People diagnosed through newborn screening and treated early often have much better outcomes. Those with late diagnosis or delayed treatment may experience serious complications affecting lifespan. With proper lifelong treatment and monitoring, many individuals live into adulthood.
There is currently no cure for Cobalamin C Disease. However, the condition can be managed effectively with lifelong treatment. Regular vitamin B12 injections, supplements, and dietary modifications help control symptoms and prevent complications. Research into gene therapy and other advanced treatments is ongoing but not yet available.
Regular B12 deficiency results from not getting enough vitamin B12 in your diet or problems absorbing it. Cobalamin C Disease is a genetic disorder where your body cannot process B12 correctly even when plenty is available. Standard B12 supplements do not work for cblC disease because the metabolic pathway is broken at a different step.
If both parents carry the MMACHC gene mutation, each child has a 25% chance of having the disease. Each child also has a 50% chance of being a healthy carrier and a 25% chance of inheriting two normal genes. Genetic counseling and carrier testing can help families understand their risks and make informed decisions about future pregnancies.
Elevated homocysteine is a key marker, often above 50 micromoles per liter compared to normal levels below 15. High methylmalonic acid in blood and urine also appears in cblC disease. Low methionine levels, anemia, and abnormal blood cell counts may also be present. Genetic testing confirms the diagnosis by identifying MMACHC gene mutations.
Yes, some people with milder forms of cblC disease do not show symptoms until adolescence or adulthood. Late-onset cases may present with psychiatric symptoms, cognitive decline, or blood disorders rather than the severe infant symptoms. Adult-onset cases are less common but still require the same treatment approach.
Monitoring frequency depends on age and how stable the condition is. Newly diagnosed patients may need testing every few weeks to adjust treatment. Once stable, most people need blood tests every 3 to 6 months to check homocysteine and methylmalonic acid levels. Your metabolic specialist will determine the best schedule based on your individual response to treatment.
A low-protein diet is often recommended to reduce production of methylmalonic acid. Your metabolic dietitian will calculate safe protein limits based on age and body size. High-protein foods like meat, fish, eggs, dairy, beans, and nuts may need to be limited. Special medical foods designed for metabolic disorders may be prescribed to meet nutritional needs.
Yes, many states now include cblC disease in expanded newborn screening panels. The screening test measures levels of certain amino acids and organic acids in a blood spot taken from the baby's heel. Early detection through screening allows treatment to begin before symptoms appear, which significantly improves outcomes and prevents brain damage.
Pregnancy is possible but requires careful planning and monitoring with a high-risk obstetric team and metabolic specialist. Treatment must be continued throughout pregnancy with close monitoring of blood levels. Pregnant women with cblC disease face higher risks of complications including blood clots and preeclampsia. Preconception counseling is essential to plan the safest approach.