Congenital transcobalamin II deficiency presenting atypically with a low
serum cobalamin level: studies demonstrating the coexistence of a
circulating transcobalamin I (R binder) complex
R Carmel and Y Ravindranath
A case of transcobalamin II deficiency with several unique features is
described. The clinical presentation was typical, except for a slightly
delayed age at presentation and the occurrence of apparent neurologic
dysfunction from the beginning. The unusual biochemical feature was a low
serum cobalamin level (97 pg/ml). Several cobalamin-binding protein
abnormalities coexisted and antedated cobalamin therapy. Chief among these
was the complexing of all serum R binder (transcobalamin I), leaving the
patient with no detectable R binder. This defect appeared to be transient.
Noteworthy, too, was a prominent binder of 70,000 mol wt that also carried
the bulk of his serum cobalamin after therapy; it was prominent in his
presumably heterozygous relatives too. The interrelationship between all
these abnormalities is intriguing but unclear. The abnormality in
transcobalamin II deficiency is clearly not limited solely to deficiency of
transcobalamin II. It is also evident that this entity must now be
considered in the differential diagnosis of low serum cobalamin levels in
infancy.
Volume 63,
Issue 3,
pp. 598-605,
03/01/1984
Copyright © 1984 by The American Society of Hematology
