Compare the microcytic families

Established iron deficiency commonly shows low ferritin, low serum iron and TSAT, increased TIBC or transferrin, and increased RDW. Early deficiency can affect storage and availability before marked microcytosis or anemia develops. The pattern supports depleted stores but does not identify why iron is deficient.

Inflammation or functional iron restriction can show low iron and TSAT with normal or increased ferritin and low or normal transferrin. Renal disease requires kidney-function context and the laboratory iron panel. A normal CRP reduces but does not eliminate inflammation as a confounder.

Marked microcytosis with a relatively high RBC count, normal iron context, and target cells supports a thalassemia-pattern differential. The Mentzer index is MCV (fL) ÷ RBC count (× 10^12/L); a value below 13 is a screening clue that can help select further evaluation, not a diagnostic discriminator. Hemoglobin analysis may be appropriate when combined CBC, smear, and iron context leave that differential, while alpha-thalassemia may require molecular investigation.

Sideroblastic processes can show increased iron, ferritin, and TSAT. Dimorphism means two visibly distinct red-cell populations and may support mixed erythropoiesis, transfusion effect, or a sideroblastic process. Ring sideroblasts are erythroid precursors with perinuclear iron-laden mitochondria on a marrow iron stain; they are not visible on a peripheral smear and require marrow interpretation in context. Coarse basophilic stippling is aggregated ribosomal RNA visible as coarse blue granules in red cells; it can support a lead-related differential but is not specific for lead exposure.