Disorder in which the body has adequate iron stores, but is unable to incorporate the iron into hemoglobin.

Causes: - Genetic (eg, X-linked defect in ALA synthase gene)- Acquired (myelodysplastic syndromes)- Reversible (alcohol is most common; also lead, vitamin B₆ deficiency, copper deficiency, isoniazid, chloramphenicol)

Lab findings:- ↑ iron, normal/↓ TIBC, ↑ ferritin- Ringed sideroblasts (with iron-laden, Prussian blue-stained mitrochondria) seen in bone marrow- Peripheral blood smear: basophilic stippling of RBCs

Treatment: Pyridoxine (B₆, cofactor for δ-ALA synthase)