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, she is pale with a hemoglobin of 7.2 g/dL. Blood smear shows microcytic, hypochromic RBCs with anisocytosis. Serum ferritin is 12 ng/mL (normal 30–300), and serum iron is 35 μg/dL (normal 60–170). TIBC is 420 μg/dL (normal 250–425). What is the most likely diagnosis?

Explanation

## Diagnosis: Iron Deficiency Anemia ### Clinical Presentation This patient has a classic presentation of iron deficiency anemia (IDA): - **Duration:** Progressive symptoms over 6 months - **Risk factor:** Heavy menstrual bleeding (most common cause of IDA in women of reproductive age) - **Symptoms:** Fatigue, dyspnea on exertion, palpitations - **Exam finding:** Pallor ### Laboratory Findings | Parameter | Patient Value | Normal Range | Interpretation | |-----------|---------------|--------------|----------------| | Hemoglobin | 7.2 g/dL | 12–16 (F) | Moderate anemia | | RBC morphology | Microcytic, hypochromic | Normocytic, normochromic | Iron deficiency pattern | | Serum ferritin | 12 ng/mL | 30–300 | **Depleted iron stores** | | Serum iron | 35 μg/dL | 60–170 | **Low** | | TIBC | 420 μg/dL | 250–425 | **Elevated** (compensatory) | | Transferrin saturation | ~8% | 20–50% | **Low** | **Key Point:** The combination of **low ferritin + low serum iron + elevated TIBC** is pathognomonic for iron deficiency anemia. Ferritin <15 ng/mL has >95% specificity for depleted iron stores. ### Pathophysiology 1. Chronic blood loss (menorrhagia) → depleted iron stores 2. Reduced iron absorption → decreased hemoglobin synthesis 3. Microcytic, hypochromic RBCs produced 4. Elevated TIBC reflects upregulation of transferrin synthesis in response to low circulating iron **High-Yield:** Iron deficiency anemia is a **microcytic, hypochromic anemia with elevated TIBC and low ferritin**. This distinguishes it from thalassemia (normal/elevated ferritin) and anemia of chronic disease (low TIBC). ### Differential Diagnosis at a Glance | Feature | IDA | Thalassemia Trait | Anemia of Chronic Disease | Sideroblastic | |---------|-----|-------------------|---------------------------|---------------| | Ferritin | ↓ | Normal/↑ | Normal/↑ | ↑ | | Serum iron | ↓ | Normal/↑ | ↓ | ↑ | | TIBC | ↑ | Normal | ↓ | Normal | | RBC count | Normal/↓ | ↑ | Normal/↓ | Normal/↓ | | Mentzer index (MCV/RBC) | >13 | <13 | Variable | Variable | **Clinical Pearl:** The **Mentzer index** (MCV ÷ RBC count) is useful: <13 suggests thalassemia; >13 suggests iron deficiency. This patient's microcytosis with low ferritin and elevated TIBC makes IDA the clear diagnosis.