Definition: large MCV indicating large RBCs

Can be megalobastic or non-megaloblastic

Megaloblastic - Impaired DNA synthesis preventing the cell from dividing normally, Rather than dividing it keeps growing into a larger, abnormal cell This is caused by a vitamin deficiency

Megaloblastic anaemia

Characterised by the presence in the bone marrow of erythroblasts with delayed nuclear maturation because of defective DNA synthesis (megaloblasts) - a block in DNA synthesis

• megaloblasts are large and have immature nuclei

Megaloblastic anaemia is caused by:

• B12 deficiency or abnormal B12 metabolism
• Folate deficiency or abnormal folate metabolism
• Other defects of DNA synthesis - e.g. congenital enzyme deficiencies, drugs interfering with DNA synthesis 1. (e.g.hydroxycarbamide (hydroxyurea), azathioprine)

Haemotology findings:

• MCV over 96fL unless there is coexisting cause of microcytosis in which case there may be a dimorphic picture
• Blood film: oval macrocytes with hypersegmented polymorphs with six or more lobes in the nucleus
• Severe cases: leucopenia, thrombocytopenia
• LDH is typically elevated reflecting ineffective erythropoeisis