transcobalamin 2 deficiency
An autosomal recessive disorder (OMIM:275350) with onset in early infancy, which is characterised by failure to thrive, megaloblastic anaemia, and pancytopenia, variably accompanied by methylmalonic aciduria, recurrent infections, vomiting and diarrhoea.
Prognosis Poor if untreated (cobalamin), which may lead to mental retardation and neurologic defects.
Molecular pathology Defects of TCN2, which encodes transcobalamin 2, a vitamin B12-binding protein, cause transcobalamin 2 deficiency.
Synonyms TC II deficiency, TCN2 deficiency, transcobalamin II deficiency