The term “megaloblastic” may infer any of the blood cell maturation lines. Megaloblastic anemia is not to be confused with macrocytic anemia. Where megaloblastic anemia is due to faulty DNA synthesis, macrocytic anemia is a secondary problem due to a primary disorder such as  liver disease,  acute hemorrhage, or  severe anemic episode. Macrocytic anemia is characterized by a MCV range of 105 to 115 fL (indicating thin cells or target cells), although the MCV may go from 100 fL to 130 fL and if severe, may be up to 160 fL. The retic count tends to run from 10 to 25% where it is normal for a megaloblastic condition. In megaloblastic anemia the MCV may range from 100 fL to 160 fL with the MCH elevated but the MCHC is usually normal.
Clinical symptoms for the macrocytic and megaloblastic anemia include  pallor,  mouth soreness,  glossitis,  lethargy,  asthenia,  anorexia,  weight loss,  diarrhea followed by constipation, and  headaches. In megaloblastic anemia, the patient may also experience  paresthesia (numbness in hands and feet), and  changes in proprioception (movement, posture, and equilibrium). If the condition is not corrected, the patient may experience sudden involuntary movements or convulsions and progress to ataxia (defective movements). This is a progressive disease in which the spinal cord may degenerate and/or the patient may become psychotic.
The psychotic stage is known as megaloblastic madness. Megaloblastic anemic disorders are vitamin-dependent of which pernicious anemia describes a condition caused by the absence of intrinsic factor resulting in a B12 deficiency. Other causes may be due to increased requirements for B12 and/or folic acid. Drugs, malabsorption, and dietary deficiencies have been known to contribute to the manifestation of this anemic disorder.