Differential Diagnosis for Low MCV, High Red Blood Cells, and High RDW

Single Most Likely Diagnosis

• Iron Deficiency Anemia: This condition is characterized by a low Mean Corpuscular Volume (MCV) indicating microcytic anemia, an increased number of red blood cells (RBCs) as the body tries to compensate for the lack of iron, and a high Red Cell Distribution Width (RDW) reflecting the variation in size of the red blood cells. The high RDW is particularly indicative of iron deficiency anemia as it suggests a significant variation in red blood cell size, which is common in this condition.

Other Likely Diagnoses

• Thalassemia: This genetic disorder affects the production of hemoglobin, leading to microcytic anemia (low MCV). It can also cause an increase in the number of red blood cells as the body attempts to compensate for the inefficient oxygen delivery. The RDW can be elevated due to the variability in red blood cell size.
• Chronic Disease Anemia: Conditions like chronic kidney disease or chronic infections can lead to a microcytic anemia with an increased RDW. The body's response to chronic disease can also result in an elevated RBC count in some cases.
• Anisocytosis: This condition is characterized by a significant variation in the size of red blood cells, which would explain the high RDW. It can be associated with various forms of anemia, including those with low MCV and potentially elevated RBC counts.

Do Not Miss Diagnoses

• Polycythemia Vera: Although this myeloproliferative disorder typically presents with an elevated hematocrit and often macrocytic red cells, in early stages or with co-existing iron deficiency, it could present with microcytic anemia and an elevated RBC count. The high RDW could be seen due to the variation in cell size. Missing this diagnosis could be critical due to the risk of thrombotic events.
• Myelodysplastic Syndromes (MDS): These disorders can present with a variety of cytopenias or cytoses, including anemia with a low MCV and high RDW. An elevated RBC count could be seen in some subtypes. MDS can progress to acute leukemia, making early diagnosis crucial.

Rare Diagnoses

• Sideroblastic Anemia: This rare condition is characterized by the presence of ringed sideroblasts in the bone marrow and can present with microcytic anemia, elevated RBC count in some cases, and a high RDW due to the variability in red blood cell size.
• Congenital Disorders of Hemoglobin Synthesis: Besides thalassemia, other rare genetic disorders affecting hemoglobin production could lead to microcytic anemia with variable effects on RBC count and RDW.