SUBACUTE COMBINED DEGENERATION WITH HIGH SERUM VITAMIN-B12 LEVEL AND ABNORMAL VITAMIN-B12 BINDING-PROTEIN - NEW CAUSE OF AN OLD SYNDROME

Subacute combined degeneration of the spinal cord due to vitamin B-12 deficiency invariably has been associated with a low serum vitamin B-12 level. We describe a young man who presented with a unique syndrome of subacute combined degeneration associated with high serum vitamin B-12 level, low red blood cell vitamin B-12 level, and an abnormal plasma vitamin B-12-binding protein. Uptake of cobalamin by his leukocytes in vitro was inhibited by his own but not by normal control plasma. Intensive hydroxocobalamin (vitamin B-12) treatment was associated with clinical and electrophysiologic recovery accompanied by normalization of mean corpuscular volume, red blood cell vitamin B-12 level, plasma homocysteine, and urinary methylmalonic acid. The subacute combined degeneration was probably precipitated by treatment with folic acid as the significance of his high serum vitamin B-12 level was not apparent when he first presented with megaloblastic anemia 3 years earlier. To our knowledge, this is the first example of neurologic disease associated with high serum vitamin B-12 level and provides further evidence that sometimes a serum vitamin B-12 level may not be a reliable guide to vitamin B-12 deficiency.