A 45-year-old woman presents with fatigue, exertional dyspnea, and pallor. Her complete blood count shows hemoglobin 8.5 g/dL, MCV 72 fL, and RDW 18%. Her serum ferritin is 8 ng/mL (normal 15-200 ng/mL), and transferrin saturation is 10% (normal 20-50%). What is the most likely underlying cause of her anemia?
✓ Correct Answer: Option D
The patient has microcytic, hypochromic anemia with elevated RDW. The very low ferritin and transferrin saturation are classic indicators of iron deficiency anemia. Vitamin B12 deficiency causes macrocytic anemia. Thalassemia trait typically has low MCV but normal RDW and ferritin.