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• "Functional" Vitamin B12 Deficiency
  Lawrence R. Solomon
  Published on: 14 April 2016
• Clinical signs and symptoms emphasized.
  Ivy A.E. Ekem
  Published on: 14 April 2016

• Published on: 14 April 2016

  "Functional" Vitamin B12 Deficiency

  • Lawrence R. Solomon, Physician

  Dear Editor,

  I read with interest the important case report of Turner and Talbot describing clinical subacute combined degeneration in a patient with “functional” vitamin B12 deficiency (defined by elevated levels of the B12 -dependent metabolites, methylmalonic acid and homocysteine, despite normal serum B12 values).1 It is important to note that although their patient did not improve with hydroxycobalamin the...

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  Dear Editor,

  I read with interest the important case report of Turner and Talbot describing clinical subacute combined degeneration in a patient with “functional” vitamin B12 deficiency (defined by elevated levels of the B12 -dependent metabolites, methylmalonic acid and homocysteine, despite normal serum B12 values).1 It is important to note that although their patient did not improve with hydroxycobalamin therapy, progression of her disease was halted. This pattern is consistent with B12 deficiency since neurologic changes become irreversible if B12 therapy is delayed for more than 6 months.2

  Importantly, functional vitamin B12 deficiency may be far more prevalent than classic B12 deficiency where serum vitamin B12 levels are clearly depressed.3 Moreover, recent reports suggest that vitamin B12 therapy can indeed improve neuropathy in some patients with functional B12 deficiency as well as in some patients with normal B12, methylmalonic acid and homocysteine values.3-5 Finally, B12, methylmalonic acid and homocysteine values have been shown to fluctuate widely in untreated individuals.3 Thus, when the clinical picture is consistent with B12 deficiency, therapeutic trials of B12 should be considered regardless of the results of B12 and metabolite testing.

  References

  1. Turner MR, Talbot K.
  Functional vitamin B12 deficiency.
  Practical Neurology 2009; 9:37-45.

  2. Chanarin I.
  The Megaloblastic Anaemias, 2nd Edition, Oxford, UK.
  Blackwell Scientific Publications, 1979:287-290.

  3. Solomon LR.
  Cobalamin-responsive disorders in the ambulatory care setting” unreliability of cobalamin, methylmalonic acid and homocysteine testing.
  Blood 2005; 105:978-985.

  4. Solomon LR.
  Disorders of cobalamin (vitamin B12) metabolism: emerging concepts in pathophysiology, diagnosis and treatment.
  Blood Reviews 2007; 21:113-130.

  5. Nardin RA, Amick ANH, Raynor EM.
  Vitamin B12 and methylmalonic acid levels in patients presenting with polyneuropathy.
  Muscle Nerve 2007; 36:532-535.

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  Conflict of Interest:
  None declared.

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• Published on: 14 April 2016

  Clinical signs and symptoms emphasized.

  • Ivy A.E. Ekem, Haematologist

  Dear Editor,

  I wish to commend the authors for their paper on functional vitamin B12 deficiency.

  It is important that despite the array of investigative tools that may be available at the disposal of clinicians, clinical signs and symptoms are given their due emphasis particularly in Vitamin B12 deficiency. The authors report a case where the serum cobalamin was normal in the face of anaemia and neurol...

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  Dear Editor,

  I wish to commend the authors for their paper on functional vitamin B12 deficiency.

  It is important that despite the array of investigative tools that may be available at the disposal of clinicians, clinical signs and symptoms are given their due emphasis particularly in Vitamin B12 deficiency. The authors report a case where the serum cobalamin was normal in the face of anaemia and neurological damage, at the other end of the spectrum are cases with normal haemoglobin levels but with significant morbidity. A recent report by Rajkumar AP and Jebaraj P (1) was of a non anaemic patient with psychosis who returned to complete self care following treatment with Vitamin B12.

  The diagnostic value of properly elicited clinical signs and symptoms cannot be overemphasized.

  Reference

  1. Chronic Psychosis associated with Vitamin B12 deficiency.
  J Assoc Physicians India 2008 Feb; 56: 115-6

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  Conflict of Interest:
  None declared.

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