[Cobalamin metabolism disorders in adult patients]

Disorders of cobalamin metabolism include defects of absorption, transport and intracellular metabolism of cobalamin. Most of the patients present in the first years of life with haematological abnormalities and feeding difficulties but some of them have later onset form and can present with pure neurological manifestations.

The suggestive clinical picture is a subacute neurological disorder similar to those observed in case of insufficient B12 intake or Biermer disease. In this frame, additional diagnosis clues could be associated megaloblastic anemia, previous history of venous thrombosis, association with psychiatric disturbances, involvement of both central and peripheral nervous system. The key investigations are measurement of plasma amino acid levels and urinary organic acid, which allow to detect abnormalities consistent with intracellular cobalamin deficiency. Treatment depends on the metabolic defect but usually consist in intramuscular cobalamin supplementation. It results in stabilization or improvement in most cases.

Because this treatable condition can lead to death or irreversible neurological damage, we recommend that disorder of the cobalamin metabolism should be consider in all young adults with unexplained consistent neurological manifestations.