Schematic of erythroid differentiation. Once red blood cells lose their nucleus, maturation of reticulocyte takes place in bone marrow for 1-3 days and then the peripheral blood.
Schematic of red blood cell indices as reticulocytes differentiate into mature red blood cells. Reticulocytes are larger than mature red blood cells (average mean cell volume [MCV] about 115 fL). As they mature, reticulocytes lose their remaining RNA and organelles, their volume is reduced by about 20% volume and they acquire a biconcave shape. The total amount of intracellular hemoglobin (mean cell hemoglobin, MCH) does not change (there is no appreciable loss or gain of hemoglobin molecules). Thus, the mean cell hemoglobin concentration (MCHC) must decrease.
A real case. Complete blood counts from a 66 year-old man with GI bleeding in July 2021. On July 29, 2021, the reticulocyte count was 150 x 109/L, and this elevation corresponded to an increase in the mean cell volume (MCV) and a decrease in the mean corpuscular hemoglobin concentration (MCHC).
