Rather than pale and small RBC’s (hypochromic microcytic) which you’d find in iron deficiency anemia, the red blood cells look huge in megaloblastic anemia.
The two main causes of megaloblastic anemia are either a folic acid deficiency or a B12 deficiency. Another name for a B12 deficiency is cyanocobalamin deficiency. The most damaging is the B12/cyanocobalamin deficiency (known specifically as pernicious anemia) because it can cause nerve damage. Before nerve damage occurs though, the signs are megaloblastic anemia.
Replacement with the wrong vitamin can mask the deficiency: If you give a person folic acid, the persons RBC go back to looking normal. If they have a B12 deficiency and you give them folic acid, their RBC go back to looking normal as well but the nerve damage is still occurring because they still have a B12 deficiency.
Deficiency Comparison
Cyanocobalamin
- Irreversible nerve damage
- Constipation
Folic Acid
- No Nerve Damage
- Diarrhea
