Overview
This lecture introduces the classification of anemias into underproduction and destruction types, explains how to differentiate them using reticulocyte count, and describes sub-classification based on red blood cell size.
Classification of Anemias
- Anemias are divided into underproduction and destruction types.
- Underproduction anemias result from insufficient creation of red blood cells.
- Destruction anemias occur when red blood cells are produced normally but are destroyed or lost after production.
Diagnostic Tool: Reticulocyte Count
- Reticulocyte count measures the number of immature red blood cells (“reticulocytes”).
- Normal reticulocyte count is about 3%.
- Destruction anemias show a reticulocyte count higher than 3% (bone marrow compensation).
- Underproduction anemias show a reticulocyte count lower than 3% (inadequate bone marrow response).
Sub-classification of Underproduction Anemias
- Underproduction anemias are further classified by red blood cell size, measured as MCV (mean corpuscular volume).
- Normal MCV range is 80–100.
- Macrocytic anemia: MCV > 100 (red blood cells larger than normal).
- Microcytic anemia: MCV < 80 (red blood cells smaller than normal).
- Normocytic anemia: MCV 80–100 (normal sized red blood cells).
Causes Based on RBC Size
- Macrocytic anemias are generally caused by a shortage of DNA precursors.
- Microcytic anemias are typically caused by deficient or abnormal hemoglobin production.
- Normocytic anemias include most other types of underproduction anemias.
Key Terms & Definitions
- Anemia — deficiency of red blood cells or hemoglobin.
- Underproduction anemia — anemia due to insufficient production of red blood cells.
- Destruction anemia — anemia due to excessive loss or destruction of red blood cells.
- Reticulocyte — an immature red blood cell.
- Reticulocyte count — percentage of reticulocytes in the blood, indicates bone marrow activity.
- MCV (Mean Corpuscular Volume) — average volume of individual red blood cells.
- Macrocytic anemia — anemia with large red blood cells (MCV > 100).
- Microcytic anemia — anemia with small red blood cells (MCV < 80).
- Normocytic anemia — anemia with normal-sized red blood cells (MCV 80–100).
Action Items / Next Steps
- Review the causes and examples of macrocytic, microcytic, and normocytic anemias in more detail.