What condition is indicated by a high RBC count combined with very low MCV and normal RDW?

The combination of a high red blood cell (RBC) count, very low mean corpuscular volume (MCV), and normal red cell distribution width (RDW) is indicative of thalassemia.

Thalassemia is a genetic disorder characterized by reduced production of hemoglobin, resulting in microcytic anemia. In this condition, the body compensates by producing more red blood cells to carry oxygen. This leads to an elevated RBC count while the MCV remains low because the individual red cells are smaller in size than normal. Additionally, the RDW is usually normal in thalassemia since the red blood cells are consistent in their size, unlike in iron deficiency anemia, where a higher RDW would generally be observed due to varying cell sizes.

This clinical picture is distinct from conditions like vitamin B12 deficiency, iron deficiency anemia, and sideroblastic anemia, which typically present with different hematological profiles. For instance, vitamin B12 deficiency often presents with macrocytic anemia (high MCV), iron deficiency anemia showcases high RDW, and sideroblastic anemia may have various MCV changes depending on the underlying cause. Thus, the unique combination of findings in this scenario clearly points to thalassemia as the correct