Difference between MCHC NCNC Dimorphic anemia slide
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MCHC NCNC dimorphic anemia peripheral blood smear differences morphology
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Peripheral Blood Smear: MCHC vs NCNC vs Dimorphic Anemia
1. Normochromic Normocytic (NCNC) Anemia
Figure: Normal peripheral smear showing the NCNC pattern - uniform RBCs, 6-8 µm diameter, central pallor ≤ 1/3 of cell diameter (Henry's Clinical Diagnosis, Fig. 31.9)
| Feature | Finding |
|---|---|
| RBC size | Normal (6-8 µm), matches nucleus of small lymphocyte |
| RBC color | Normal pink staining - central pallor present but ≤ 1/3 of cell |
| Uniformity | Uniform in size and shape - minimal anisocytosis or poikilocytosis |
| MCV | Normal (80-100 fL) |
| MCH | Normal |
| MCHC | Normal (32-36 g/dL) |
| RDW | Normal (11-14%) |
| RBC histogram | Normal bell-shaped curve |
Causes: Aplastic anemia, acute blood loss (early), hemolytic anemia (most), anemia of chronic disease (early/mild), renal failure (EPO deficiency), hypothyroidism (mild)
2. Microcytic Hypochromic (MCHC decreased) Anemia
Figure: Microcytic hypochromic RBCs in iron deficiency anemia - central pale area exceeds 1/3 of the cell (Henry's Clinical Diagnosis, Fig. 31.10)
| Feature | Finding |
|---|---|
| RBC size | Small (< 6 µm) - microcytes |
| RBC color | Pale/washed out - central pallor > 1/3 (hypochromia) |
| Uniformity | Anisocytosis and poikilocytosis often present; pencil cells, target cells in thalassemia |
| MCV | Low (< 80 fL) |
| MCH | Low (< 27 pg) |
| MCHC | Low (< 32 g/dL) - this is the hallmark |
| RDW | Elevated in iron deficiency; normal/near-normal in thalassemia trait |
| RBC histogram | Left-shifted (narrow peak shifted leftward) |
Causes: Iron deficiency anemia (most common), thalassemia, anemia of chronic disease (severe/longstanding), lead poisoning, congenital sideroblastic anemia (the hypochromic population)
Key point on MCHC: MCHC is the ratio of hemoglobin to cell volume. When hemoglobin synthesis is impaired (iron deficiency, thalassemia), cells are small AND pale - both MCV and MCHC drop. Thalassemia trait has a low MCV but relatively preserved MCHC compared to iron deficiency, along with a normal RDW.
3. Dimorphic Anemia
Figure: Dimorphic anemia - two distinct RBC populations: microcytic hypochromic cells alongside normocytic (and even macrocytic) cells, with marked anisocytosis and anisochromia (Henry's Clinical Diagnosis, Fig. 31.13)
| Feature | Finding |
|---|---|
| RBC size | TWO populations - small microcytes AND normal/large cells coexist |
| RBC color | TWO populations - hypochromic cells AND normochromic cells coexist (anisochromia) |
| Uniformity | Marked anisocytosis and anisochromia - this is the defining feature |
| MCV | Can be normal (the two populations "cancel out") or elevated |
| MCH | Variable |
| MCHC | Variable - may appear normal due to mixed populations |
| RDW | Markedly elevated (> 14.5%) - reflects the wide variation in cell size |
| RBC histogram | Bimodal curve (two peaks) - pathognomonic |
Causes:
- Sideroblastic anemia (classic cause) - hypochromic microcytes from defective heme synthesis + normochromic/macrocytic cells; ringed sideroblasts on bone marrow
- Iron deficiency + B12/folate deficiency combined - microcytic hypochromic + macrocytes
- Iron deficiency responding to treatment - new normochromic cells appear alongside old hypochromic cells
- Post-transfusion in hypochromic anemia - transfused normochromic cells + patient's hypochromic cells
- Myelodysplastic syndrome (MDS)
- Erythropoietin therapy in chronic renal failure
Side-by-Side Comparison Table
| Parameter | NCNC | Microcytic Hypochromic (low MCHC) | Dimorphic |
|---|---|---|---|
| RBC populations | One uniform | One - all small/pale | Two distinct populations |
| Cell size | Normal | Small (microcytic) | Mixed: small + normal/large |
| Central pallor | ≤ 1/3 | > 1/3 (hypochromic) | Mixed: pale + normal |
| MCV | Normal | Low | Normal or high |
| MCHC | Normal | Low | Variable/normal |
| RDW | Normal | High (IDA) / Normal (thal) | Markedly high |
| RBC histogram | Bell-shaped | Left-shifted | Bimodal |
| Anisocytosis | Absent/mild | Moderate | Marked |
| Anisochromia | Absent | Absent | Present (defining feature) |
| Key clue on smear | Uniform, normal cells | All cells pale & small | Two "flavors" of RBC visible |
Key Distinguishing Points at a Glance
- NCNC: Every cell looks the same - normal size, normal color. Think hemolysis, renal failure, aplastic anemia early phase.
- Low MCHC (microcytic hypochromic): Every cell looks the same but wrong - all small and pale. Think iron deficiency (RDW elevated) or thalassemia (RDW normal, basophilic stippling, target cells).
- Dimorphic: The smear has two clearly different RBC populations visible simultaneously. Think sideroblastic anemia (classic), or iron deficiency mid-treatment, or combined nutritional deficiency. The RDW is strikingly elevated and the automated histogram shows a bimodal pattern.
Sources: Henry's Clinical Diagnosis and Management by Laboratory Methods (Figs. 31.9, 31.10, 31.13); Goldman-Cecil Medicine (Microcytic Anemias); Harrison's Principles of Internal Medicine 22E (Ch. 65 - Interpreting Peripheral Blood Smears); Rosen's Emergency Medicine
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