Vitamins B9 and B12 Deficiencies
Megaloblastic anemia is a macrocytic anemia that is usually caused by either a vitamin B9 or a vitamin B12 deficiency. They are characterized by the presence of hypersegmented neutrophils in the peripheral blood, in addition to elevated homocysteine levels. Tests writers love asking you to decide between folate and cobalamin deficiency, and there are a number of distinguishing characteristics. First, B12 deficiency is characterized by neurologic symptoms, as myelin is affected in a process known as subacute combined degeneration. Specifically, the lateral corticospinal tract, spinocerebellar tract, and dorsal columns are affected. Moreover, labs will show elevated methylmalonic acid levels, which should further help you distinguish it. On the other hand, B9 deficiency occurs before B12 deficiency, as the liver has a smaller reserve pool of folate. It is a common vitamin deficiency in alcoholics, and this is a fact that is commonly tested.