5.2 - Microcytic anemia Flashcards
what are the 4 etiologies of microcytic anemia?
- iron deficiency
- anemia of chronic disease
- sideroblastic anemia
- thalassemia
where does iron absorption occur?
duodenum
which is more readily absorbed: heme or non-heme form of iron?
heme
enterocytes transport iron across the cell membrane via ___________
ferroportin
___________ transports iron in the blood and delivers it to liver and bone marrow macrophages for storage
transferrin
stored intracellular iron is bound to __________
ferritin
what laboratory measurement is used to measure iron in the blood?
serum iron
what laboratory measurement is used to measure the amount of transferrin molecules in the blood?
TIBC
what laboratory measurement assesses the percentage of transferrin molecules that are bound by iron?
% sat
what is the normal % sat for iron?
33%
what laboratory measurement reflects iron stores in macrophages and the liver?
serum ferritin
which hookworms are responsible for iron deficiency?
- ancylostoma duodenale
- necator americanus
iron is more readily absorbed in a(n) _____________ (acidic / basic) environment
acidic
why does an acidic environment aid iron absorption?
maintains Fe2 state
the very initial stage of iron deficiency anemia is ________________ (microcytic / normocytic / megaloblastic)
normocytic
what is the RDW in iron deficiency anemia?
increased
what are the following values for iron deficiency anemia?
- ferritin
- TIBC
- serum iron
- % sat
- ferritin: low
- TIBC: high
- serum iron: low
- % sat: low
what is the free erythrocyte protoporphyrin level in iron deficiency anemia? why?
increased - there is no problem with the protoporphyrin production
what is the triad in plummer vinson syndrome?
- iron deficiency
- esophageal web
- glossitis
what are the two ways hepcidin sequesters iron in storage sites?
- limiting iron transfer from macrophages to erythroid precursors
- suppressing EPO production
what are the following values in anemia of chronic disease?
- ferritin
- TIBC
- serum iron
- % sat
- ferritin: high
- TIBC: low
- serum iron: low
- % sat: low
what is the free erythrocyte protoporphyrin value in anemia of chronic disease?
high
ALA synthetase converts ____________ to __________ using ___________ as a cofactor
- succinyl CoA
- ALA
- B6
__________ attaches protoporphyrin to iron to make heme
ferrochelatase
sideroblasts form due to iron laden ____________ which surround the __________ of erythroid precursors
- macrophages
- nucleus
lead inhibits which two enzymes of heme biosynthesis?
- ALA dehydratase (ALA to porphobilinogen)
- ferrochelatase
what are the following values in sideroblastic anemia?
- ferritin
- TIBC
- serum iron
- % sat
- ferritin: high
- TIBC: low
- serum iron: high
- % sat: high
thalassemia confers resistance to plasmodium ___________
FALCIPARUM
what are the normal types of Hb?
- HbF (a2y2)
- HBA (a2B2)
- HbA2 (a2d2)
alpha thalassemia is due to a gene __________
deletion
how many genes are there in alpha thalassemia? which chromosome?
- 4
- 16
which is worse: cis deletion of two alpha chains, or trans deletion? which population has this?
- cis
- Asians
HbH is formed by a deletion of ____ alpha genes from chromosome ____
- 3
- 16
Hb Barts is formed by a deletion of _____ alpha genes from chromosome ____
- all 4
- 16
beta thalassemia is due to a gene ___________
mutation
how many genes are there in beta thalassemia? which chromosome?
- 2
- 11
which has target cells - alpha thal or beta?
beta
electophoresis shows slightly decreased HbA with increased HbA2 and HbF - which type of thalassemia?
beta thal minor (B/B plus)
why does beta thal major take several months to present?
HbF (a2y2) is temporarily protective
- hepatosplenomegaly
- chipmunk facies
- crew cut appearance on x ray
beta thal major
what treatment is necessary for beta thal major? what is a possible sequela of treatment?
- chronic transfusions
- hemochromatosis (secondary)
what does a blood smear show for beta thal major?
- microcytic hypochromic RBCs
- target cells
- nucleated RBCs
what does electrophoresis show for beta thal major?
- HbA2
- HbF
little to no HbA
