Differential Diagnosis for Elevated Red Blood Cells with Decreased MCV, MCH, MCHC, and Low Ferritin

• Single Most Likely Diagnosis

  • Iron deficiency anemia: This is the most likely diagnosis due to the combination of elevated red blood cell count (which can occur in the early stages of iron deficiency as the body tries to compensate for the lack of iron), decreased mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC) indicating microcytic hypochromic anemia, and low ferritin levels which directly indicate depleted iron stores.

• Other Likely Diagnoses

  • Thalassemia: This genetic disorder affects the production of hemoglobin, leading to microcytic anemia. While ferritin might not always be low, the microcytic hypochromic indices and elevated red blood cell count could suggest thalassemia, especially in individuals of certain ethnic backgrounds.
  • Chronic disease: Chronic diseases such as chronic infections, inflammatory conditions, or malignancies can lead to anemia of chronic disease, which may present with low ferritin due to inflammation-induced sequestration of iron, despite adequate iron stores.

• Do Not Miss Diagnoses

  • Polycythemia vera: Although less likely given the microcytic hypochromic anemia, polycythemia vera (a myeloproliferative disorder) can sometimes present with elevated red blood cell counts. It's crucial to rule out this condition due to its potential for serious complications, including thrombosis.
  • Hemoglobinopathies: Other hemoglobinopathies, like sickle cell disease or hemoglobin C disease, could potentially present with microcytic anemia and should be considered, especially if there are other clinical or familial hints towards these conditions.

• Rare Diagnoses

  • Sideroblastic anemia: This is a group of rare disorders where the bone marrow fails to utilize iron to create hemoglobin, leading to microcytic anemia with elevated ferritin levels typically, but in some cases, ferritin might be low, especially if there's a component of iron deficiency.
  • Erythrocytosis due to hypoxia: Conditions leading to chronic hypoxia (e.g., high-altitude living, chronic obstructive pulmonary disease) can cause an increase in red blood cell production. While typically normocytic, in the setting of concomitant iron deficiency, the indices could be microcytic.