The Imerslund-Graesbeck Syndrome (IGS) is a rare cause of megaloblastic anemia that appears during childhood.
Synonyms: selective vitamin B12 malabsorption with proteinuria, hereditary megaloblastic anemia Type 1, juvenile megaloblastic anemia
The receptor in the ileum for the vitamin B12 and intrinsic factor complex is composed of 2 proteins, cubulin and amnionless. Cubulin is also located in the proximal renal tubules, where it is complexed with megalin for receptor-mediated tubular reabsorption of certain ligands..
Protein
Gene
Locus
cubilin
CUBN
10p12.1
amnionless
AMN
14q32
Inheritance: autosomal recessive
Clinical features:
(1) onset of megaloblastic anemia during childhood (from infancy to adolescence)
(2) failure to thrive
(3) recurrent infections
(4) neurological findings consistent with cobalamin deficiency
(5) variable proteinuria (occurs with mutation in cubilin)
(6) exclusion of other causes of megaloblastic anemia, with an adequate dietary intake
(7) clinical response to parenteral vitamin B12
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