A 42-year-old man from Delhi presents with progressive fatigue, dyspnea, and palpitations for 3 months. He reports a history of peptic ulcer disease treated with omeprazole for 5 years. On examination: BP 110/70, HR 96/min, conjunctival pallor present. Laboratory: Hemoglobin 8.5 g/dL, MCV 68 fL, RBC count 5.2 × 10⁶/µL, reticulocyte count 1.2%, serum ferritin 18 ng/mL, serum B₁₂ 280 pg/mL (low-normal), serum folate 6.2 ng/mL (low-normal). Peripheral blood smear: microcytic hypochromic RBCs, occasional hypersegmented neutrophils. What is the most likely cause of anemia in this patient?

Explanation

## Diagnostic Analysis: Combined Micronutrient Deficiency ### Clinical Context **Key Point:** This patient has a **dual deficiency state**—iron AND B₁₂ deficiency—secondary to long-term PPI use. Both are present, and both contribute to the anemia. ### Why PPIs Cause Multiple Deficiencies ```mermaid flowchart TD A[Long-term PPI use]:::action --> B[Reduced gastric acid]:::outcome B --> C1[Impaired iron absorption]:::outcome B --> C2[Reduced intrinsic factor secretion]:::outcome B --> C3[Bacterial overgrowth in stomach]:::outcome C1 --> D1[Iron deficiency]:::urgent C2 --> D2[B₁₂ malabsorption]:::urgent C3 --> D3[Possible folate depletion]:::outcome D1 --> E[Microcytic hypochromic anemia]:::outcome D2 --> F[Megaloblastic changes]:::outcome E --> G[Mixed picture: microcytic + hypersegmented neutrophils]:::outcome F --> G ``` ### Laboratory Interpretation | Parameter | Value | Interpretation | |-----------|-------|----------------| | Hemoglobin | 8.5 g/dL | Moderate anemia | | MCV | 68 fL | **Microcytic** (< 80 fL) | | RBC count | 5.2 × 10⁶/µL | **Elevated** (normal 4.5–5.5) | | Reticulocyte count | 1.2% | Low-normal (inadequate response) | | Ferritin | 18 ng/mL | **Depleted iron stores** (< 30 = IDA) | | B₁₂ | 280 pg/mL | **Low-normal** (< 300 = deficiency) | | Folate | 6.2 ng/mL | **Low-normal** (< 7 = deficiency) | | Peripheral smear | Microcytic + hypersegmented neutrophils | **Mixed picture** | **High-Yield:** The combination of **microcytic RBCs + hypersegmented neutrophils** is pathognomonic for combined iron and B₁₂ deficiency. Iron deficiency alone would NOT show hypersegmented neutrophils. ### Why This Is Combined Deficiency 1. **Iron deficiency component:** - Ferritin 18 ng/mL confirms depleted iron stores. - Microcytic RBCs (MCV 68) reflect iron-limited hemoglobin synthesis. - PPI-induced hypochlorhydria impairs non-heme iron absorption. 2. **B₁₂ deficiency component:** - B₁₂ 280 pg/mL is low-normal (< 300 pg/mL = deficiency). - Hypersegmented neutrophils on smear indicate megaloblastic changes (B₁₂ deficiency). - PPIs reduce intrinsic factor secretion, impairing B₁₂ absorption. 3. **Why MCV is microcytic, not macrocytic:** - **Iron deficiency dominates the MCV** because iron is needed for every RBC. - B₁₂ deficiency causes nuclear maturation defects (megaloblasts), but if iron is limiting, cells are smaller. - This creates a **"dimorphic" picture**—two populations of RBCs (microcytic + some macrocytic), averaging to microcytic. **Clinical Pearl:** When you see microcytic anemia + hypersegmented neutrophils, always think **combined iron and B₁₂ deficiency**. The microcytic RBCs are iron-deficient; the hypersegmented neutrophils reflect B₁₂ deficiency affecting nuclear maturation in all cell lines. ### Management Implications - **Oral ferrous sulfate 200 mg daily** for iron replacement. - **Vitamin B₁₂ supplementation:** IM cyanocobalamin 1000 µg weekly × 6 weeks, then monthly maintenance (oral absorption is impaired). - **Stop PPI or switch to H₂-blocker** if possible to prevent ongoing deficiency. - **Recheck CBC in 6–8 weeks:** MCV should rise (B₁₂ effect) and Hb should improve (iron + B₁₂). **Warning:** If you treat only iron deficiency and ignore B₁₂ deficiency, the patient will develop subacute combined degeneration (neurological complications: paresthesia, ataxia, dementia).