Transcobalamin deficiency is a disorder that impairs the transport of cobalamin (also known as vitamin B12) within the body. Cobalamin is obtained from the diet; this vitamin is found in animal products such as meat, eggs, and shellfish. An inability to transport cobalamin within the body results in cells that lack cobalamin, which they need for many functions including cell growth and division (proliferation) and DNA production. The absence of cobalamin leads to impaired growth, a shortage of blood cells, and many other signs and symptoms that usually become apparent within the first weeks or months of life.

Mutations in the TCN2 gene cause transcobalamin deficiency. The TCN2 gene provides instructions for making a protein called transcobalamin. This protein attaches (binds) to cobalamin and transports the vitamin to cells throughout the body. Within cells, cobalamin helps certain enzymes carry out chemical reactions. Cobalamin plays a role in the processes that produce the building blocks of DNA (nucleotides) and break down various compounds such as fatty acids; these processes are needed for cell proliferation and the production of cellular energy.

The prevalence of transcobalamin deficiency is unknown. At least 45 affected individuals have been described in the medical literature.

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Published Date: October 01, 2014
Published By: National Institutes of Health