Abstract
Transcobalamin (transcobalamin II, TC) transports plasma vitamin B12 (cobalamin, Cbl) into cells. TC deficiency is a rare autosomal recessive disorder causing intracellular Cbl depletion, which in turn causes megaloblastic bone marrow failure, accumulation of homocysteine and methylmalonic acid, and methionine depletion. The clinical presentation reflects intracellular Cbl defects, with early-onset failure to thrive with gastrointestinal symptoms, pancytopenia, and megaloblastic anemia, sometimes followed by neurological complications. We report the clinical, biological, and molecular findings and the outcome in five TC-deficient patients. The three treated early had an initial favorable outcome, whereas the two treated inadequately had late-onset severe neuro-ophthalmological impairment. Even if the natural course of the disease over time might also result in late-onset symptoms in the aggressively treated patients, these data emphasize that TC deficiency is a severe disorder requiring early detection and probably long-term aggressive therapy. Mutation analysis revealed six unreported mutations in the TCN2 gene. In silico structural analysis showed that these mutations disrupt the Cbl-TC interaction domain and/or the putative transcobalamin–transcobalamin receptor interaction domain.
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The authors are grateful to Dr. Kevin Collins for his critical review and constructive comments on this article.
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Communicated by: Matthias Baumgartner
Competing interests: None declared.
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Schiff, M., Ogier de Baulny, H., Bard, G. et al. Should transcobalamin deficiency be treated aggressively?. J Inherit Metab Dis 33, 223–229 (2010). https://doi.org/10.1007/s10545-010-9074-x
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DOI: https://doi.org/10.1007/s10545-010-9074-x