A 38-year-old woman from rural Maharashtra presents with progressive fatigue, dyspnea on exertion, and palpitations for 6 months. She reports heavy menstrual bleeding for the past 2 years. On examination: pallor present, conjunctival pallor noted, no lymphadenopathy or splenomegaly. Blood investigations: Hb 7.2 g/dL, MCV 62 fL, MCH 19 pg, RBC 5.8 × 10¹²/L, serum iron 32 μg/dL (normal 60–170), TIBC 420 μg/dL (normal 250–425), ferritin 8 ng/mL (normal 12–200). Peripheral blood smear shows microcytic hypochromic RBCs with occasional target cells. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Iron Deficiency Anemia (IDA) ### Key Diagnostic Features **Key Point:** The combination of microcytic hypochromic anemia with low serum iron, elevated TIBC, and low ferritin in a woman with menorrhagia is pathognomonic for iron deficiency anemia. ### Laboratory Interpretation | Parameter | Value | Interpretation | |-----------|-------|----------------| | Hb | 7.2 g/dL | Moderate anemia | | MCV | 62 fL | Microcytic (< 80 fL) | | MCH | 19 pg | Hypochromic (< 27 pg) | | Serum iron | 32 μg/dL | Low (normal 60–170) | | TIBC | 420 μg/dL | Elevated (normal 250–425) | | Ferritin | 8 ng/mL | **Diagnostic: < 12 ng/mL confirms iron deficiency** | | RBC count | 5.8 × 10¹²/L | Elevated (paradoxically high in IDA) | **High-Yield:** In iron deficiency anemia, the RBC count is often **normal or elevated** because the body compensates by producing more RBCs, even though each is smaller and paler. This distinguishes IDA from thalassemia, where RBC count is markedly elevated (often > 6.5 × 10¹²/L) with proportionally lower Hb. ### Pathophysiology of Iron Deficiency 1. **Chronic blood loss** (menorrhagia) → depletion of iron stores 2. **Depleted ferritin** → reduced iron availability for hemoglobin synthesis 3. **Reduced heme synthesis** → microcytic (small RBCs) and hypochromic (pale RBCs) 4. **Compensatory erythropoiesis** → increased RBC production (hence RBC count may be normal or high) 5. **Peripheral smear findings:** - Microcytic hypochromic RBCs (dominant) - Target cells (due to reduced hemoglobin content) - Occasional pencil cells (elliptocytes) - Anisocytosis and poikilocytosis ### Iron Metabolism in IDA **Key Point:** In iron deficiency, the body upregulates iron absorption and mobilization: - **Serum iron ↓** (depleted body stores) - **TIBC ↑** (increased transferrin synthesis to maximize iron capture) - **Transferrin saturation ↓** (iron/TIBC ratio < 16%) - **Ferritin ↓** (depleted iron stores; most specific marker) **Clinical Pearl:** Ferritin < 12 ng/mL is **diagnostic of iron deficiency** in the absence of inflammation. In this patient, ferritin 8 ng/mL confirms absolute iron deficiency. ### Etiology in This Patient **Menorrhagia** (heavy menstrual bleeding) is the most common cause of IDA in non-pregnant women in developed countries and increasingly in India. Normal menstrual loss is 30–40 mL/cycle; menorrhagia is defined as > 80 mL/cycle. Chronic blood loss exceeds the body's ability to absorb dietary iron (~1–2 mg/day), leading to progressive depletion. ### Why This Is NOT Thalassemia Trait **Warning:** Thalassemia trait (β-thalassemia minor) also presents with microcytic hypochromic anemia and is common in India. However, the **ferritin is normal or elevated** in thalassemia (iron overload from repeated transfusions or ineffective erythropoiesis). Additionally, RBC count in thalassemia is typically **> 6.5 × 10¹²/L** (much higher than in IDA), and serum iron and TIBC are normal. **Mnemonic: TIBC in IDA vs. Thalassemia** - **IDA:** Low iron, **High TIBC**, Low ferritin - **Thalassemia:** Normal iron, **Normal TIBC**, Normal/High ferritin