Which of the following anemias is characterized by a reticulocyte count that is inappropriately low relative to the degree of anemia?

Explanation

## Reticulocyte Response in Anemias **Key Point:** The reticulocyte count reflects the bone marrow's erythropoietic response. In anemias due to decreased RBC production, the reticulocyte count is inappropriately low (often <2%) relative to the severity of anemia. ### Classification by Reticulocyte Response | Anemia Type | Reticulocyte Count | Mechanism | Examples | | --- | --- | --- | --- | | **Hypoproliferative** | Low (<2%) | Decreased RBC production | Iron deficiency, B12/folate deficiency, aplastic anemia, chronic kidney disease | | **Hyperproliferative** | High (>2%) | Increased RBC production (appropriate response) | Hemolysis, acute hemorrhage, hemoglobinopathies | **High-Yield:** Iron deficiency anemia is the classic example of a hypoproliferative anemia where the reticulocyte count fails to rise appropriately despite significant anemia. The bone marrow cannot produce RBCs efficiently due to lack of iron substrate. **Clinical Pearl:** A patient with Hb 7 g/dL and reticulocyte count <2% suggests a production problem (iron deficiency, B12 deficiency, aplastic anemia), not a loss/destruction problem. Conversely, a high reticulocyte count with anemia indicates appropriate marrow response to hemolysis or blood loss. ### Why Other Options Are Wrong - **Hemolytic anemia:** Shows brisk reticulocytosis (often >10%) as the marrow appropriately responds to RBC destruction - **Acute hemorrhage:** Triggers appropriate reticulocyte rise within 3–5 days - **Hemoglobin H disease:** A hyperproliferative hemolytic state with elevated reticulocytes