Earliest manifestation of megaloblastic anemia is
(Ref: Harrison 18/e p866, 17/e p645-646, Tejinder Singh 2/e p54-61)
 




Peripheral blood picture


Bone marrow picture





Macrocytosis (↑ MCV, MCH. Normal MCHC)
Peripheral smear

           Macroovalocytes
           Few nucleated RBCs
           Evidence of dyserythropoiesis like-

Basophilic stippling
Cabot ring
Howell- Jolly bodies


↓ Hb
↓ Hematocrit
Reticulocyte count – Normal or mild decrease
White cells- Leucopenia
Hypersegmented neutrophils/ Macropolycytes- First manifestation 
↓ Platelets
Pancytopenia (10-20%)

   Lab investigations:

Serum iron, ferritin - ↑ in pure VitB12/ Folate defect
Serum bilirubin & LDH ↑- due to hemolytic component
Schillings test: Used to assess status of intrinsic factor (IF) & Vit B12 to distinguish pernicious anemia from other causes of Vit.B12  deficiency.




Moderate- marked hypercellularity
Erythroid hyperplasia
M:E ratio reversal
Erthropoiesis- Megaloblastic
Giant metamyelocytes
Mildly reduced megakaryocytes
BM iron moderately increased in pure Vit B12/ Folate defects.
Macrocytosis
Hypersegmented neutrophils
Basophilic stippling
Cabot ring