Abstract
Methylmalonic Acidemia and Megaloblastic Anemia due to Congenital Intrinsic Factor Deficiency
Highlights
Causes of vitamin B12 deficiency in children include decreased intake, abnormal absorption, and inborn errors of B12 transport and metabolism
We describe a 2 year old male who presented with severe megaloblastic anemia and methylmalonic acidemia
Patients with intrinsic factor deficiency (IFD) present with pancytopenia and megaloblastic anemia and unlike Imerslund-Grasbeck syndrome (IGS), cobalamin malabsorption is corrected by intrinsic factor administration [3,4]
Summary
Causes of vitamin B12 deficiency in children include decreased intake, abnormal absorption, and inborn errors of B12 transport and metabolism. Rare causes of cobalamin malabsorption include Imerslund-Grasbeck syndrome (IGS) and intrinsic factor deficiency (IFD). Patients with IFD present with pancytopenia and megaloblastic anemia and unlike IGS, cobalamin malabsorption is corrected by intrinsic factor administration [3,4]. In 2004, a specific GIF mutation was first identified as a cause of severe anemia and cobalamin deficiency in an 11 year old girl [3]. We describe a 2 year old male who presented with megaloblastic anemia and methylmalonic acidemia, leading to a diagnosis of congenital gastric intrinsic factor deficiency through genetic testing. Few cases have been described with our patient’s specific GIF heterozygous mutation c.79+1G>A and no cases with the novel variant c.960C>A [1,4] His presentation with markedly elevated methylmalonic acid initial suspicion of myelodysplastic syndrome is unique. Homocysteine and methylmalonic acid levels were increased while vitamin B12 levels were decreased (Table 1)
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