Long-term Outcome of a Patient With Transcobalamin Deficiency Caused by Tcn2 Mutation: A Case Report

Abstract

Background:Transcobalamin deficiency is a rare autosomal recessive inborn error of cobalamin transport (prevalence: <1/1000000)whichclinically manifests in early infancy. Case presentation:We describe the case of a 30 year old woman who at the age of 30 days presented with the classical clinical and laboratory signs of an inborn error of vitamin B12 metabolism. Family history revealed a sister who died at the age of 3 months with a similar clinical syndrome and with pancytopenia.Shewas started on empirical intramuscular (IM) cobalamin supplements (injections of hydroxocobalamin 1 mg/day for 1 week and then 1 mg twice a week) and several transfusions of washed and concentrated red blood cells.With thesetreatments a clear improvement in symptoms was observed, with the disappearance of vomiting, diarrhea and normalization of the full blood count.At 8 years of age injections were stopped for 3 monthscausing the reappearance of megaloblastic anemia.IM hydroxocobalamin was then restartedsine die.The definitive diagnosis could only be established at 29 years of age when a genetic evaluation revealed homozygous nonsense variation in exon 8 of the TCN2 gene.Currently she is a 30-year old healthy lady taking 1 mg of IM hydroxocobalamin once a week.Conclusions: Our case report highlights that early detection of TC deficiency and early initiation of aggressive IM treatment is likely associated with disease control and an overall favorable outcome.