Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Imerslund-Grasbeck syndrome ?
    ### Response:
    Imerslund-Grasbeck syndrome (IGS) is a rare condition characterized by vitamin B12 deficiency, often causing megaloblastic anemia. IGS usually appears in childhood. Other features may include failure to thrive, infections, and neurological damage. Mild proteinuria (with no signs of kidney disease) is present in about half of affected individuals.
    