Combined congenital deficiencies of intrinsic factor and R binder.

Coexisting deficiencies of both intrinsic factor (IF) and R binder were identified in an Algerian boy who presented with severe megaloblastic anemia, growth retardation, and neurologic dysfunction with typical features of subacute combined degeneration of the spinal cord. The anemia responded completely to cyanocobalamin and folic acid. IF was absent from gastric juice, but acid secretion and gastric mucosa were normal. R binders were absent from gastric juices as well as from serum, saliva, and polymorphonuclear leukocytes. The patient's father exhibited absence of R binder in his serum with a low serum vitamin B12 level and was asymptomatic. This unique case of simultaneous IF and R binder deficiencies suggests a genetic association between these two functionally and immunologically dissimilar, but structurally close vitamin B12-binding proteins.