Free cobalamin does not bind to the ileal receptor (IR), a specific receptor located on the brush border. Only the cobalamin/intrinsic-factor complex binds to IR.It is a very rare cause of congenital megaloblastic anaemia also known as Ileal receptor congenital deficiency. In addition to megaloblastic anaemia this syndrome of malabsorption exhibits infections and neuropathy.

Synonym: Ileal receptor congenital deficiency