Final answer:
Reduced MCV in a patient with untreated rheumatoid arthritis typically suggests anemia of chronic disease, characterized by altered iron studies such as increased ferritin, decreased TIBC, and low transferrin saturation.
Step-by-step explanation:
A patient with a long history of untreated rheumatoid arthritis and reduced mean corpuscular volume (MCV) is likely experiencing anemia of chronic disease. This type of anemia can be characterized by several iron study indicators: increased ferritin levels due to inflammation, decreased total iron-binding capacity (TIBC), and low transferrin saturation. These changes reflect altered iron metabolism where the body intentionally sequesters iron in storage sites, preventing proper utilization for red blood cell (RBC) production.
Anemias are typically broken down into three groups: those caused by blood loss, faulty or decreased RBC production, and those caused by excessive destruction of RBCs. In rheumatoid arthritis, the anemia is often due to faulty or decreased RBC production, associated with chronic inflammation. Important diagnostic tests, apart from MCV and iron studies, include reticulocyte counts which may reveal inadequate production of RBCs.