Subacute combined degeneration with high serum vitamin B12 level and abnormal vitamin B12 binding protein. New cause of an old syndrome
E. H. Reynolds, T. Bottiglieri, M. Laundy, J. Stern, J. Payan, J. Linnell and J. Faludy
Department of Neurology, King's College Hospital, Denmark Hill, London, England.
Subacute combined degeneration of the spinal cord due to vitamin B12
deficiency invariably has been associated with a low serum vitamin B12
level. We describe a young man who presented with a unique syndrome of
subacute combined degeneration associated with high serum vitamin B12
level, low red blood cell vitamin B12 level, and an abnormal plasma vitamin
B12-binding protein. Uptake of cobalamin by his leukocytes in vitro was
inhibited by his own but not by normal control plasma. Intensive
hydroxocobalamin (vitamin B12) treatment was associated with clinical and
electrophysiologic recovery accompanied by normalization of mean
corpuscular volume, red blood cell vitamin B12 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 B12 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 B12
level and provides further evidence that sometimes a serum vitamin B12
level may not be a reliable guide to vitamin B12 deficiency.
