Module 2: Hypochromic Anemias Flashcards
Disorders of iron metabolism (2)
Iron deficiency anemia (IDA)
- decreased dietary iron
- blood loss
- impaired iron transport
Anemias of chronic disease (ACH)
- Chronic inflammatory diseases
- Malignant disorders
Disorders of Heme synthesis (Sideroblastic anemias) (3)
Hereditary Sideroblastic Anemia Idiopathic Sideroblastic Anemia Secondary Sideroblastic Anemia -Drug induced -Alcohol induced -Lead poisoning
Disorders of Globin synthesis (thalassemias) (3)
Beta thalassemia
alpha thalassemia
other thalassemia
Function of iron (3)
formation of heme
component of cytochromes, catalase, myeloperoxidase
Enzyme activator in some reactions
Total body iron content in adults
2-5grams
Iron distribution % in the body
Heme (enzymes, hemoglobin, myoglobin) 80%
Transport (transferrin) 0.1%
Storage (spleen, liver, other) 20%
Source of daily iron
diet provides 15mg per day
5-10% of this is absorbed into circulation (1.0-1.5mg)
Pregnant and menstruating women need more
where is iron mostly absorbed
mostly in duodenum and jejunum
What is iron absorption dependent on (3)
serum iron concentration (inversely): Amount of circulating iron
Amount in the diet (directly)
pH in the gut - an acid pH enhances absorption (inversely)
Other things that may vary iron absorption
Reducing agents that enhance it (vit c)
Phytates and phosphates form insoluble iron complexes that decrease absorption
Alcohol enhances absorption by stimulating Hal secretion
Large amount of dairy product interfere with conversion of ferric iron to ferrous iron
What state must iron be in to be absorbed
reduced, ferrous state (Fe 2+)
Iron transport
in plasma, iron is transported by transferrin to areas of utilization (NRBC in BM, storage in macrophages and hepatic cells)
normal transferrin saturation with iron
30%
meaning 30% of the iron binding sites available on transferrin are occupied by iron
2 forms of Iron storage
ferritin (major normal storage form)
Hemosiderin
Ferritin
water soluble (temporary) storage of iron in NRBC, intestinal mucosal cells, renal tubular cells, plasma and macrophages (mostly in liver and spleen)
Not large enough to be visible in RBC
when is ferritin converted to hemosiderin
prolonged storage
Hemosiderin
water insoluble storage of iron
Formed in macrophages by polymerization of many ferritin into large dense iron aggregates
Visible in cells using Prussian blue stain
Presence may indicate iron overload
Pappenheimer bodies
hemosiderin in cells when stained with wrights stain
Iron excretion
no form of excretion
Some is lost every day and must be replaced by diet or iron stores will be depleted
Causes of iron deficiency (4)
decreased intake
incomplete or inadequate absorption
increased utilization
iron loss
Cause of Iron deficiency: Decreased Iron intake
Nutritional deficiency
Most common cause of IDA in infants
Due to: Malabsorption, elderly and impoverished, fad diets, meat poor diets
Cause of Iron deficiency: Incomplete or inadequate iron absorption
Iron is not absorbed in GI tract
Due to: Celiac disease, resection of small bowel, absence of factors required for absorption
Cause of Iron deficiency: Increased iron utilization
Increased demand for iron that is not met
Due to: Pregnancy, growth spurts, increased need of RBC regeneration
Cause of Iron deficiency: Iron loss
Acute or chronic bleeding (most common cause of IDA in canada)
Due to: GI/ urinary bleed, intravascular hemolysis, malignancy, menstruation, pregnancy
Iron deficiency anemia
an anemia of severely decreased or absent body iron stores
results in decreased heme formation in developing NRBC as well as hypochromia and microcytosis in mature RBC
Hypochromia
red cells with increased central pallor, indicating they contain less hemoglobin than normal
3 stages of Iron deficiency anemia
iron depletion
iron deficiency
iron deficiency anemia
Iron depletion stage of IDA lab results
Stage 1
Hb N
Serum iron N
TIBC (total iron binding capacity) N
Ferritin Decreased
Iron deficiency stage of IDA lab results
Stage 2
Hb N
Serum iron Decreased
TIBC Increased
Ferritin decreased
Iron deficiency anemia lab results hematology
Hb decreased
Hit decreased
RBC indices decreased
RBC morph: Mild: hypochromia, microcytosis
Severe: plus ovalocytes and target cells
Iron deficiency anemia lab results chemistry
Iron Assay Decreased
TIBC increased
Transferrin saturation decreased
Ferritin decreased
sTfR increased
FEP increased
Iron assay
measures amount of circulating iron that is bound to transferrin
TIBC total iron binding capacity
measures ability of transferrin to carry iron
Transferrin saturation
measured as percentage
Ratio of serum iron to TIBC
(serum iron/TIBC) x100
Serum ferritin
measurement of storage iron levels
indirect method as levels reflect the levels of iron stores within cells
sTfR Soluble Transferrin receptor
indicated number of RBC transferrin receptors are present on the cell
Thalassemia
group of inherited disorders
rate of synthesis of specific polypeptide chain (alpha or beta) use in global production in RBC is decreased
Hypochromia, microcytic
Sideroblastic anemia
caused by biochemical abnormalities in synthesis of heme
NOT due to lack of iron
Iron accumulates because protoporphyrin IX formation is decreased
Classification of sideroblastic anemias
Refractory: inherited; idiopathic
Secondary: due to Vit b6 deficiency, drugs/toxins that inhibit enzymes of heme synthesis (lead intoxication), malignancies
3 ways lead disrupts normal function in Sideroblastic anemia of lead poisoning (plumbism)
1) interfere with enzymes of heme synthesis resulting in hypochromia
2) interfere with enzymes which normally depolymerize RNA in RBC resulting in basophilic stippling
3) interfere with membrane ATPase enzymes required for active transport = premature hemolysis of developing RBC and ineffective erythropoiesis
Anemia of chromic disorders (3 causes)
seen in inflammatory diseases
1) inflammatory blockage of release of iron stores; mild accumulation of iron in storage areas and deficiency in developing RBC
2) Increase hemolysis of RBC
3) Decreased erythropoietin production
Lab results of Iron Deficiency Anemia (IDA)
Serum Iron: D TIBC: I Transferrin saturation: D Serum ferritin: D sTfR: I Storage iron (BM iron stain): absent
Lab results of Beta Thalassemia
HB electrophoresis: Increased HbA2
Lab results for Anemia of Chronic Disease (ACD)
Serum Iron: D TIBC: D Serum Ferritin: I FEP: I Storage iron (BM iron stain): normal in macrophages; decreased in NRBC
Lab results for Sideroblastic Anemias
Serum Iron: I TIBC: N Transferrin saturation: I Serum ferritin: I sTfR: D Storage iron (BM iron stain): I RBC morph: dimorphic, basophilic stippling and pappenheimer bodies Bone marrow: Ringed sideroblasts
