Transcobalamin II deficiency

Transcobalamin II deficiency is a rare, inherited disorder that affects the body's ability to properly absorb and use vitamin B12 (cobalamin). Vitamin B12 is essential for the production of DNA, the maintenance of the nervous system, and the formation of red blood cells. Transcobalamin II is a protein that binds to vitamin B12 in the blood plasma, facilitating its transport into cells where it can be utilized. A deficiency in transcobalamin II leads to a functional vitamin B12 deficiency, as the vitamin cannot be effectively delivered to the cells that need it.

Causes

Transcobalamin II deficiency is caused by mutations in the TCN2 gene, which provides instructions for making the transcobalamin II protein. These mutations are inherited in an autosomal recessive pattern, meaning that an individual must inherit two copies of the mutated gene (one from each parent) to be affected by the condition.

Symptoms

The symptoms of transcobalamin II deficiency can vary widely among affected individuals but typically manifest in early infancy. Common symptoms include:

• Failure to thrive
• Megaloblastic anemia
• Diarrhea
• Immunodeficiency, leading to increased susceptibility to infections
• Neurological problems such as developmental delay, muscle weakness, and movement disorders

Diagnosis

Diagnosis of transcobalamin II deficiency typically involves a combination of clinical evaluation, laboratory testing, and genetic testing. Laboratory tests may show megaloblastic anemia and low levels of vitamin B12 in the blood. However, since transcobalamin II is responsible for transporting vitamin B12, its deficiency can lead to normal or high levels of vitamin B12 in the blood with low levels in the cells. Genetic testing can confirm a diagnosis by identifying mutations in the TCN2 gene.

Treatment

Treatment for transcobalamin II deficiency focuses on managing symptoms and preventing complications. This typically involves regular injections of vitamin B12 to bypass the need for transcobalamin II in vitamin B12 transport. Early diagnosis and treatment are crucial to prevent potentially irreversible neurological damage.

Prognosis

The prognosis for individuals with transcobalamin II deficiency varies depending on the severity of symptoms and the timing of diagnosis and treatment. With early and ongoing treatment, many of the complications of the disorder, particularly those related to anemia and growth, can be managed effectively, allowing for a better quality of life.

Transcobalamin II deficiency Resources
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