Differential Diagnosis for High Red Blood Cell Count with Low MCV, Low MCH, Low MCHC, and High RDW

• Single Most Likely Diagnosis

  • Iron Deficiency Anemia: This condition is characterized by a decrease in the mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC), along with an increase in red blood cell distribution width (RDW). The high RDW indicates a significant variation in red blood cell size, which is typical in iron deficiency anemia. Although the CBC shows a high red blood cell count, this could be a response to chronic hypoxia or other compensatory mechanisms.

• Other Likely Diagnoses

  • Thalassemia: These genetic disorders affect hemoglobin production, leading to variable degrees of anemia, low MCV, MCH, and MCHC. The high RDW can be seen due to the presence of a range of red blood cell sizes. However, thalassemia typically presents with a low red blood cell count or anemia, making this less likely given the high red blood cell count.
  • Anisopoikilocytosis (Variation in Red Blood Cell Size and Shape): This can be seen in various conditions, including but not limited to, iron deficiency anemia, and can result in a high RDW. The presence of a high red blood cell count might be secondary to another underlying condition.
  • Chronic Disease: Certain chronic diseases can lead to a normocytic or microcytic anemia with increased RDW due to the body's inflammatory response affecting erythropoiesis. The high red blood cell count could be a compensatory response.

• Do Not Miss Diagnoses

  • Polycythemia Vera: Although this myeloproliferative disorder typically presents with an increase in all three blood cell lines (erythrocytosis, leukocytosis, and thrombocytosis), it's crucial not to miss it due to its potential for serious complications like thrombosis. The low MCV, MCH, and MCHC might not be typical, but the high RDW could indicate a complex underlying pathology.
  • Sickle Cell Disease: While typically associated with normocytic or macrocytic anemia, sickle cell disease can sometimes present with microcytosis, especially if there's co-existing iron deficiency. The high RDW is consistent with the disease's effect on red blood cells.

• Rare Diagnoses

  • Sideroblastic Anemia: This group of disorders is characterized by the presence of ringed sideroblasts in the bone marrow and can present with microcytic, hypochromic anemia and increased RDW. It's less common and might not be the first consideration but should be kept in mind, especially if other diagnoses are ruled out.
  • Other Rare Hemoglobinopathies: Besides thalassemia and sickle cell disease, other hemoglobinopathies can present with similar laboratory findings. These are less common and often require specific diagnostic tests for identification.