Among the most prevalent hematologic abnormalities in patients with rheumatologic disorders are the anemia of chronic disease (ACD), a mild anemia that is generally asymptomatic, and iron deficiency anemia.

In iron-deficiency anemia, the TIBC would higher than 400–450 mcg/dL because stores would be low.

Patients with RA occasionally have concurrent iron deficiency anemia and ACD. When this occurs, the hemoglobin level usually drops to below 9.5 g/dL, and the MCV is less than 80.

https://www.uptodate.com/contents/hematologic-manifestations-of-rheumatoid-arthritis

FA 2018 page 409. Associated with inflammation (RA, SLE, CKD).

This one is fairly logical if you remember that bacteria LOVE our iron. So much so, that our body came up with a way around it. When an infection is detected by the body, it makes like a doomsday prepper and batons down the hatches.

"All the iron into the bones, quick (^ferritin)! Hide it from the intruders! Get those iron delivery trucks (ferritin) off the road (blood)!

with decreased ferritin comes a decrease capacity for binding iron in the blood

ACD is common in patients with rheumatologic diseases such as SLE; it is the result of increased hepcidin secretion mediated by increased concentrations of inflammatory cytokines.

This results in the increased retention of iron within the RES and impaired iron exportation for use in erythropoiesis with consequent anemia.

• Ferritin concentrations: normal to increased.
• Serum iron concentrations: low.
• TIBC: low.