Differential Diagnosis for Low MCV and High RDW
Single Most Likely Diagnosis
- Iron Deficiency Anemia: This is the most common cause of low MCV (microcytic) and high RDW (red cell distribution width), indicating a variation in red blood cell size. Iron deficiency leads to insufficient hemoglobin production, resulting in smaller (microcytic) red blood cells and a wide range of cell sizes.
Other Likely Diagnoses
- Thalassemia: A genetic disorder affecting hemoglobin production, leading to microcytic anemia. While it typically presents with a low RDW due to uniform small cell size, some forms can have a high RDW, especially in cases of thalassemia trait or when co-inherited with other hemoglobinopathies.
- Anisocytosis due to Chronic Disease: Chronic diseases, such as chronic kidney disease or chronic infections, can lead to a mixed picture of anemia, including microcytosis and an increased RDW due to the body's varied response to the underlying disease process.
- Sideroblastic Anemia: A disorder where the bone marrow fails to utilize iron to create hemoglobin, leading to microcytic anemia and potentially an increased RDW due to the presence of ringed sideroblasts and variable red cell sizes.
Do Not Miss Diagnoses
- Mixed Anemia (Iron Deficiency + Vitamin Deficiency): It's crucial not to miss a mixed anemia, where iron deficiency coexists with a deficiency in either vitamin B12 or folate. The presence of both microcytic and macrocytic anemias can result in a normocytic mean corpuscular volume (MCV) but a high RDW, indicating a wide range of red blood cell sizes.
- Myelodysplastic Syndrome (MDS): A group of disorders caused by poorly formed or dysfunctional blood cells, which can present with a high RDW and microcytic anemia among other cytopenias. MDS is critical to diagnose due to its potential progression to acute myeloid leukemia.
Rare Diagnoses
- Congenital Disorders of Glycosylation: Rare genetic disorders affecting glycoprotein synthesis, which can lead to microcytic anemia and increased RDW among a constellation of other systemic symptoms.
- Hemoglobinopathies other than Thalassemia: Certain hemoglobinopathies, like hemoglobin E disease, can present with microcytosis and an increased RDW, though these are less common than thalassemia or iron deficiency anemia in most populations.