A 34-year-old woman from rural Maharashtra presents with fatigue, dyspnea on exertion, and glossitis for 3 months. On examination, she has pallor and a smooth, beefy red tongue. Her hemoglobin is 7.2 g/dL with MCV 108 fL and MCH 38 pg. Peripheral blood smear shows hypersegmented neutrophils. What is the most appropriate next step in management?

Explanation

## Clinical Diagnosis The patient presents with macrocytic anemia (MCV 108 fL) with glossitis, dyspnea, and hypersegmented neutrophils on smear — classic features of megaloblastic anemia. The differential includes vitamin B12 deficiency and folate deficiency. ## Next Step in Management **Key Point:** Before initiating specific therapy for megaloblastic anemia, serum B12 and folate levels MUST be measured to identify the underlying etiology. This is the gold standard diagnostic step. **High-Yield:** Measurement of serum cobalamin and folate is the first-line confirmatory test. Normal values: B12 >200 pg/mL, folate >5.4 ng/mL. If B12 is low, proceed to methylmalonic acid and homocysteine to confirm B12 deficiency. ## Why This Approach | Finding | B12 Deficiency | Folate Deficiency | | --- | --- | --- | | Serum B12 | Low (<200 pg/mL) | Normal (>200 pg/mL) | | Serum Folate | Normal or low | Low (<5.4 ng/mL) | | Neurological signs | Present (paresthesia, ataxia) | Absent | | Glossitis | Present | Present | | Source | Pernicious anemia, dietary, post-gastrectomy | Dietary, malabsorption, drugs (MTX, TMP-SMX) | **Clinical Pearl:** Treating B12 deficiency with folate alone can mask neurological manifestations while worsening them — a critical pitfall. Conversely, folate supplementation in undiagnosed B12 deficiency accelerates subacute combined degeneration. **Tip:** The presence of hypersegmented neutrophils and glossitis strongly suggests B12 deficiency (pernicious anemia is common in India due to dietary vegetarianism and malabsorption), but confirmation is mandatory before therapy. [cite:Harrison 21e Ch 104]