Current concepts in the diagnosis of cobalamin deficiency

Abstract

Despite, or perhaps because of, a number of advances in our understanding of Cbl metabolism, we more frequently encounter patients with unusual or atypical clinical and laboratory features who have underlying Cbl deficiency. Subacute combined degeneration of the spinal cord, neuropathy, and other classic manifestations of Cbl deficiency in the nervous system are often easy to recognize, but we now know that there are many atypical presentations. ^[1-4] Some patients have neurologic syndromes without anemia or macrocytosis, whereas others have a normal serum Cbl level, yet are found to have other biochemical evidence of Cbl deficiency such as raised levels of the metabolites methylmalonic acid and homocysteine. Appropriate investigation is critical, because early treatment affords the possibility of excellent recovery.