[Pernicious anemia]

Pernicious anaemia is the most common cause of cobalamin deficiency. Nervous disorders associated with cobalamin deficiency are neuropathy, optic atrophy, dementia and myelopathy (subacute combined degeneration). In this case, symptoms are those of posterior and lateral column dysfunction of the spinal cord, with diminished vibratory sensation, ataxia, weakness of limbs, hyperreflexia, extensor plantar response and spasticity. Macrocytosis and anaemia are often lacking. There is an inverse correlation between the degree of anaemia and the extent of nervous impairment. The most sensitive tool for the diagnosis of cobalamin deficiency is the serum cobalamin level. But a normal cobalamin assay does not fully exclude cobalamin deficiency. Levels of serum methylmalonic acid and total homocysteine are useful as ancillary tests in the diagnosis. Treatment is based on intramuscular injections of vitamin B12.