microcytic anemia Flashcards
main criteria for microcytic anemia
MCV < 80fL
types of microcytic anemia
- iron deficiency
- thalassemia
- chronic inflammation
- sideroblastic
- lead poisoning
what is sideroblastic anemia?
inability to synthesize heme
what is thalassemia?
inability to synthesize globin
in terms of iron, what is the difference between iron deficiency and chronic inflammation?
- iron deficiency is the lack of iron in the body which in chronic inflammation, iron is sequestered in macrophages after they consume RBCs.
diagnostic criteria for iron deficiency
- MCV<80fL
- hypochromic smear (pale RBCs, low MCH)
- anisocytosis (increased RDW)
where is iron absorption regulated?
duodenum by hepcidin
how do we lose iron?
urine, skin, feces
causes of iron deficiency
- chronic blood loss, usually intestinal
- decreased intestinal absorption
- decreased oral intake
what can cause decreased intestinal absorption in iron deficiency?
- gastritis
- H. pylori
- bypass surgery
- celiac disease
- use of antacids
when is checking of gastrointestinal bleeding in iron deficiency patient absolutely necessary?
over age 50
signs and symptoms of iron deficiency
- S and S of anemia
- pica
- restless leg?
what is the most accurate way to assess body iron stores?
ferritin, but it can be elevated by inflammation
what happens to transferrin levels in iron deficiency?
- high, looking to bind any available iron
transferrin saturation test
- iron/transferring
- high saturation in elevated iron levels
- low saturation in low iron levels
treatment for iron deficiency
- ferrous sulfate
- sometimes iron given IV
- check underlying cause of any blood loss
what type of genetic defect is thalassemia?
autosomal recessive
what type of defect pathophysiologically is thalassemia?
- quantitative defect (not enough globin)
- defect in production of either a or b chain
a and b chain genes for globin
- beta chains are one gene on each chromosome 11 (2 loci)
- alpha chains are two genes on each chromosome 16 (4 loci)
what is pathological in alpha thalassemia?
- not enough alpha chains so there is an excess of free beta chains. the beta chains are toxic to RBC membranes
what is alpha trait?
when only 1 or 2 of the 4 loci are affected, tends to be little or no anemia but decreased MCV. don’t usually need treatment
what is hemoglobin H?
- stands for “heavy”
- when three loci are affected, beta chains form unstable tetramers
- RBCs with hemoglobin H globules hemolyse
- hepato and splenomegaly
- normal lifespan usually
- sometimes need splenectomy
what is hydrops fetalis?
- all four loci affected
- hemoglobin Bart’s (gamma aggregates)
- incompatible with life
- DNA analysis required for diagnosis, electrophoresis insufficient
what is beta-thalassemia trait?
- only one of two loci affected, one compensating for the other
- no or very mild anemia
- low MCV and RDW
what is beta-thalassemia major?
- both loci affected
- body produces fetal hemoglobin
- severe anemia
- developing red cells containing alpha chain globules lyse in the marrow
- marrow, and thus bones, expand
- ## hepato and splenomegaly
how do we diagnose beta-thalassemia major?
- electrophoresis, shows decreased hemoglobin A1 and increased fetal hemoglobin
what do you see on a thalassemia smear?
- target cells (bullseye)
- microcytic, hypochromic anemia
treatment for thalassemia?
- traits generally don’t need treatment
- symptomatic thalassemia often requires frequent blood transfusions so iron levels need to be monitored
- iron over 1000 ng/mL may require iron chelation therapy
what do all sideroblastic anemias have in common?
- ringed sideroblasts in bone marrow
- defect in heme synthesis
contrast sideroblastic anemia with porphyria
defects of heme biosynthesis in the mitochondria cause anemias while defects in the cytoplasm cause porphyries
acquired clonal/neoplastic forms of sideroblastic anemias are called….
myelodysplastic syndromes
examples of acquired metabolic sideroblastic anemias
- alcoholism
- medications
- copper deficiency
what does lead to do blood?
inhibits enzymes in heme synthesis
what do you see on a blood smear for lead poisoning?
basophilic stippling
