Methylcobalamin deficiency type cblDv1

Methylcobalamin deficiency type cblDv1 is an extremely rare inherited metabolic disorder that affects how the body processes vitamin B12 (cobalamin). Specifically, it disrupts the production of methylcobalamin, one of the two active forms of vitamin B12 that the body needs. This active form is essential for an enzyme called methionine synthase, which plays a key role in converting the amino acid homocysteine into methionine. When this process does not work properly, homocysteine builds up in the blood and urine (a condition called homocystinuria), while methionine levels become abnormally low. The disease is caused by mutations in the MMADHC gene. In the cblDv1 variant, only the methylcobalamin pathway is affected, while the other cobalamin pathway (adenosylcobalamin production) remains intact. This distinguishes it from other cblD subtypes that may affect both pathways or only the adenosylcobalamin pathway. Symptoms typically appear in infancy or early childhood and can include developmental delays, feeding difficulties, megaloblastic anemia (a type of anemia where red blood cells are abnormally large), neurological problems such as seizures and low muscle tone, and failure to thrive. Without treatment, the condition can lead to significant intellectual disability and progressive neurological damage. Treatment generally involves supplementation with hydroxocobalamin (a form of vitamin B12) and betaine to help lower homocysteine levels. Early diagnosis and prompt treatment are critical to improving outcomes, though the long-term prognosis can vary depending on how early treatment begins and how well the body responds.

Bring these to your next appointment

• Q1.How severe is my child's condition based on the specific genetic mutations found?,What is the recommended treatment plan, and how often will injections be needed?,How frequently should blood tests be done to monitor homocysteine and methionine levels?,What developmental therapies should we start, and how soon?,Are there any signs or symptoms I should watch for that would require emergency care?,What is the expected long-term outlook for my child with treatment?,Should other family members be tested for carrier status, and what are the implications for future pregnancies?

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