Long-term outcome of a patient with Transcobalamin deficiency caused by the homozygous c.1115_1116delCA mutation in TCN2 gene: a case report

Background: Transcobalamin deficiency is a rare autosomal recessive inborn error of cobalamin transport (prevalence: <1/1000000) which clinically 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. She was 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 these treatments 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 months causing the reappearance of megaloblastic anemia. IM hydroxocobalamin was then restarted sine die. The definitive diagnosis could only be established at 29 years of age when a genetic evaluation revealed the homozygous c.1115_1116delCA mutation of TCN2 gene (p.Q373GfsX38).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.