Microcytic Anemia With Heavy Menstrual Bleeding
A 45-year-old woman presents with 6 months of fatigue and heavy menstrual bleeding. She has no melena, hematemesis, or weight loss, and she takes no medications. She has no history of bleeding disorder or chronic kidney disease. Physical examination shows pale conjunctivae and a smooth tongue but no lymphadenopathy or hepatosplenomegaly. Laboratory results: hemoglobin 9.8 g/dL, MCV 72 fL, RDW 18%, ferritin 12 ng/mL, total iron-binding capacity 480 µg/dL, transferrin saturation 8%, platelets 450 × 10⁹/L, and white blood cell count 6.2 × 10⁹/L. Peripheral smear shows microcytic hypochromic red cells and pencil cells. She asks whether she needs a blood transfusion and whether iron tablets will be enough. The physician must interpret the iron studies, explain why ferritin can be misleading, and plan management.
1. How do the iron studies and smear support iron deficiency anemia, and what else should be considered?
Read the worked answer
The combination of low ferritin (12 ng/mL), low transferrin saturation (8%), high TIBC (480 µg/dL), microcytic hypochromic red cells, pencil cells, high RDW, and thrombocytosis strongly supports iron deficiency anemia. Chronic menstrual blood loss is the likely cause. The differential includes thalassemia trait, anemia of chronic disease, and sideroblastic anemia. Thalassemia trait usually has normal or high ferritin, normal RDW, target cells, and elevated HbA2; anemia of chronic disease has low TIBC, normal or high ferritin, and low transferrin saturation. Sideroblastic anemia may show ring sideroblasts and basophilic stippling. This patient does not need urgent transfusion at Hb 9.8 g/dL unless she is symptomatic with hemodynamic compromise or cardiac ischemia. The key judgement is to confirm iron deficiency, treat the cause, and avoid missing a hemoglobinopathy.
2. Why can ferritin be misleading, and what would you do if the ferritin had been 80 ng/mL?
Read the worked answer
Ferritin is an acute-phase reactant and can be normal or elevated in inflammation, infection, liver disease, malignancy, and chronic kidney disease, even when iron stores are low. Therefore a normal ferritin does not always exclude iron deficiency. If ferritin were 80 ng/mL, I would check CRP and the clinical context; in an inflammatory state, ferritin below 100 ng/mL may still be consistent with iron deficiency. Transferrin saturation, soluble transferrin receptor, reticulocyte hemoglobin content, and a therapeutic iron trial can help. I would also calculate the Mentzer index (MCV/RBC) and check HbA2 to screen for thalassemia trait. In this patient, ferritin is clearly low, so the diagnosis is secure, but the principle matters because many patients with inflammation are misclassified. The reasoning is to interpret ferritin alongside inflammatory markers and other iron parameters, not in isolation.
3. What treatment and monitoring plan do you recommend, and when would you suspect another diagnosis?
Read the worked answer
Start oral ferrous sulfate 325 mg (65 mg elemental iron) once daily or every other day; alternate-day dosing may improve absorption by avoiding hepcidin surges. Advise taking it with vitamin C or an acidic beverage and avoiding tea, coffee, calcium, and antacids around the dose. Counsel about dark stools and constipation. Recheck CBC and reticulocyte count in 2–4 weeks; hemoglobin should rise by about 1 g/dL. Continue iron for 3 months after hemoglobin normalizes to replenish stores. Refer to gynecology for menorrhagia management. If there is no response, consider nonadherence, ongoing blood loss, malabsorption (celiac disease, H. pylori, bariatric surgery), or thalassemia trait. IV iron is an option for intolerance, malabsorption, or ongoing losses. Transfusion is reserved for severe symptomatic anemia or hemodynamic instability; Hb 9.8 g/dL alone does not require it.