Pernicious anemia

From WikiCNS
Jump to: navigation, search
  • i. Due to dietary deficiency, lack of intrinsic factor or malabsorption of vitamin B12 (cyanocobalamin); causes combined systems disease (a.k.a. subacute combined degeneration) in about 40% of patients with untreated pernicious anemia; onset is gradual and uniform beginning with symmetrical paresthesias in feet or hands followed by leg stiffness, weakness, and proprioceptive deficits with unsteadiness that is worse in the dark, dementia may occur in advanced cases due to cerebral white matter changes; the blind spot that normally occurs in each eye enlarges in patients with chronic B12 deficiency (similar to that seen in tobacco and alcohol excess except there the deficiency is in thiamine rather than cobalamin)
  • ii. Microscopically see spongy vacuolation and degeneration of myelin sheaths in the thoracic region, initially in the posterior columns and later in the corticospinal and spinocerebellar tracts in the lateral columns; may also cause peripheral neuropathy and glossitis and GI disturbances in addition to the megaloblastic anemia
    • 1. thought to be caused by abnormal methylation of myelin basic protein
    • 2. vitamin B12 deficiency is usually due to autoimmune atrophic gastritis resulting in inadequate production of intrinsic factor by the gastric parietal cells
    • 3. may also cause axonal degeneration (Wallerian) and mild decreases in conduction velocity with marked decline in amplitude
  • iii. Serum B12 is the most sensitive test since not all patients will have a macrocytic anemia; high serum concentrations of cobalamin metabolites (methylmalonic acid and homocysteine) are the most reliable indicator of intracellular cobalamin deficiency; Schilling test determines the cause of the B12 deficiency
  • iv. Nitrous oxide abuse may cause similar clinical syndrome as B12 deficiency
  • v. Folic acid may correct the anemia but the neurologic deficits may worsen
  • vi. Treatment: B12 injections
Personal tools