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Gene: TCN2

Green List (high evidence)

Autosomal recessive disorder with onset in early infancy characterised by failure to thrive, megaloblastic anemia, and pancytopenia. Other features include methylmalonic aciduria, recurrent infections, and vomiting and diarrhea. Treatment with cobalamin results in clinical improvement, but the untreated disorder may result in intellectual disability and neurological abnormalities.
Well established gene-disease association. 26 pathogenic TCN2 variants have been reported in over 40 individuals; multiple mouse models. Homozygous and Compound Heterozygous TCN2 variants (deletions or insertions, nonsense mutations, and point mutations) have been reported; deletions or insertions are the most common, causing frameshifts that result in protein truncation.

Created: 7 Feb 2025, 1:15 p.m. | Last Modified: 7 Feb 2025, 1:15 p.m.

Panel Version: 1.1566

Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal

Phenotypes
Transcobalamin II deficiency MIM#275350

Publications

• 19373259
• 32841161
• 33023511
• 30124850