Iron Metabolism and M/H Anemias Flashcards
Primary function of iron in the body
Oxygen transport
6 iron compartments of the body (largest to smallest) (%)
- Hb (~67% of TBI)
- Storage (~27%)
- Myoglobin (~3.5%)
- Labile pool (~2.2%)
- Tissue iron department (~0.2%)
- Transport compartment (~0.08%); smallest but most active
6 iron compartments of the body (forms of iron)
- Hb → Hb molecule
- Storage → ferritin
- Myoglobin → myoglobin molecule
- Labile pool → Fe bound to cell membrane
- Tissue iron department → Fe in cytochromes and intracellular enzymes
- Transport compartment → Fe bound to transferrin
4 factors that influence iron absorption
- Amount and type of iron accessible from food
- Functional state of GI mucosa and pancreas
- Current iron stores
- Erythropoietic needs
3 conditions that result in an increased need for iron
- Growth periods
- Blood loss
- Diversion of iron to the fetus
Anatomic site at which iron is absrobed most efficiently
Duodenum of intestinal mucosa
Function of transferrin
Transports iron to nRBCs in BM
- iron is reduced to ferrous state and proceeds to mitochondria for insertion into protoporphyrin ring
Organelle that contains iron in erythrocyte precursors
Mitocondria
What is being measured
- Serum iron
Amount of iron (bound to transferrin) in serum/plasma
What is being measured
- TIBC
Amount of iron that transferrin can bind
What is being measured
- Serum ferritin
BM iron stores
What is being measured
- BM macrophage iron
Iron held by RE cells (“erythroblastic island”)
What is being measured
- BM sideroblasts
nRBCs that contain iron
What is being measured
- ZPP (zinc protoporphyrin) or FEP (free erythrocyte protoporphyrin)
Availability of insufficient iron to developing nRBCs; erythrocyte protoporphyrin accumulates in cell
Relationship b/w serum ferritin and bone marrow iron stores in healthy individual
↑ serum ferritin, ↓ TIBC
Peripheral smear RBC morphology that would prompt the ordering of iron studies
?
Iron deficiency anemia (IDA)
- Causes
↓ dietary intake
- infants–“milk anemia”
- children–“fast food diet lacking iron”
- adults–poor diet, GI bleeds, pregnancy
↑ loss of iron
Malabsorption
Iron deficiency anemia (IDA)
- Clinical signs and symptoms
Classic: pallor, fatigue, lethargy, shortness of breath
More specific: koilonychia, heart mumur, cravings for non-food items
Iron deficiency anemia (IDA)
- RBC count and/or Hb
- RBC may be normal initially…↓ in stage 3
- ↓ H&H (Hb
Iron deficiency anemia (IDA)
- PLT count
Increased, esp. w/ blood loss
Iron deficiency anemia (IDA)
- RBC morphology
- Hypochromia
- Microcytes
- Aniso
- Some poik, varies
Iron deficiency anemia (IDA)
- MCV
Decreased
Iron deficiency anemia (IDA)
- MCHC
Decreased
Iron deficiency anemia (IDA)
- RDW
Increased
Iron deficiency anemia (IDA)
- Retic count
Slight to moderately increased (esp after blood loss and in response to iron therapy)
Iron deficiency anemia (IDA)
- Treatment
Supplemental iron (ferrous sulfate)
Pathology/mechanism for iron deficiency anemia
- Decreased dietary intake
- Increased loss of iron
- Malabsorption
Pathology/mechanism for anemia of chronic inflammation
BM macrophages fail to give up Fe to developing RBC precursors; RBCs develop iron deficient
Pathology/mechanism for sideroblastic anemia
Group of disorders characterized by accumulation of iron in the mitochondria of nRBCs…“gets trapped”
- due to defect in heme synthesis (porphyria)
Why shouldn’t long-term iron therapy be given to a patient w/ anemia of chronic inflammation?
Keep building up in the BM macrophages??
Reasons for presence of “ringed sideroblasts” upon BM iron exam of patient w/ lead poisoning
Due to iron overload caused by decresed survival of RBCs w/ inclusions and ineffective erythropoiesis
Characteristic RBC histogram appearance one would expect to see in a patient w/ siderblastic anemia (esp. hereditary form)
pic
Color of skin w/ excess iron
Bronze diabetes
Major form in which iron is stored in the liver
Ferritin
Disease of iron metabolism characterized by excess deposition of iron in tissues; may be inherited or may develop from complication of hemolytic anemia, such as B-thalassemia major
Hemochromatosis
APR that’s incrased in inflammation; as a result iron absorption is decreased and iron release from mcrophages is blocked
Hepcidin
nRBC precursor w/ “rings of iron”
Ringed sideroblast
BM erythrocyte precursor w/ excessive iron granules (siderotic granules); visible w/ Prussian blue staining
Sideroblast
Nonnucleated RBC visible w/ Prussian blue staining
Siderocyte
