RBC I, Thalassemias and hemolytic anemias Putthoff Flashcards
where are alpha chain encoded
chromosome 16
where are the beta chains encoded
chromosome 11
where are thalassemias endemic to
mediterranean basin
tropical africa, indian continent and asia
how do thalassemias cause anemia (generally)
decreased production and lifespan
not destruction
What are the B0 mutations
no beta globin synthesis
what are the B+ mutation
reduced beta globin synthesis
most common cause of beta+ mutations
splicing mutations that affect the RNA
common mutations with B0 thalassemias
prevention mRNA
chain terminator mutations (new stop codon)
how does beta thalassemia cause anemia
deficit in HbA synthesis
hypochromic microcytic RBC with subnormal O2
diminished survival of RBC and precursors
unpaired alpha chains make insoluble inclusions
how does beta thalassemia lead to bony abnormalities
ineffective erythropoiesis leads to erythroid hyperplasia and extensive EMH
why do thalassemia patients suffer from hemochromatosis
the erythroid drive suppresses hepcidin so no neg feedback on Fe absorption. absorb more leads to iron accumulation
why is a defect in beta and alppha chain not as severe as say 2 defects in beta or 2 defects in alpha
chain production is more in balance
what is beta thalassemia major
homozygou so could be B0B0 or b+b+ or b+b0
what is beta thalassemia intermedia
B0B+ b+b+ B0B b+B
variable
severe but does not require blood transfusions
what is beta thalssemia minor
heterozygous b0 B b+B
what is clinical presentation of beta thalassemia minor
asymptomatic with mild or absent anemia, red cell abnormalities seen.
when does anemia manifest in beta thalassemia major in newborns
6-p mo when HbF switches over to HbA
What do RBC look like in beta thalassemia major
anisocytosis poikilocytosis, microcytosis, hypochromic
target cells
basophilic stippling and fragmented cells
inclusions are aggregates of alpha chains
clinical cours of beta thalassemia major
brief unless receiving blood transfusions
signs of beta thalssemia major
anemia
enlarged and distorted boney prominences
HSM
cardiac disease from hemochromatosis
how do you Tx patients with beta thalassemia major
transfusion but must also give iron chelators to prevent hemochromatosis
what will PS look like in beta thalssemia minor
RBC abnormalities like hypochromia, microcytosis, basophilic stippling and target cells
mild erythroid hyperplasia in BM
what will Hb electrophoresis show in beta thalassemia minor
increase HbA2 and normal or slightly increased HbF
Wgat dies beta thalssemia minor look like and how do you diferentiate
iron deficiency anemia
look at iron panel
also increase in HbA2 helpful
severity of alpha thalssemia depends on what
how many alpha globin genes are affected
what is Hb barts
gamma globin tetramers in newborns with alpha thalassemia
how does alpha thalassemia present in older children and adults
HbH
beta tetramers
why in HbH is anemia less severe
the beta tetramers are more soluble than alpha
what is most common cause of reduced alpha chain synthesis
gene deletion
what is silent carrier state alpha thalassemia
-/a a/a
no RBC abnormality
what are the alpha thalassemia trait varieties
- /- a/a (asian)
- /a -/a (black, asian)
what are signs of alpha thalassemia trait
microcytosis
minimal or no anemia
no abnormal physical sings
low HbA2 or normal
What is genotype for HbH disease
-/- -/a
HbH most common in what population
asian
why is there hypoxia when there are tetramers of beta globins HbH
because has extremely high affinity for O2, does not release
leads to oxidation and promotes RBC sequestration and phagocytosis
clinical signs HbH
severe anemia
what is hydrops fetalis
-/- -/- no alpha globin chain synthesis
lethal in utero
distress in 3rd trimester
clinical signs of fetus with hydrops fetalis
pallor, generalized edema, massive HSM
What is Paroxysmal nocturnal Hbinuria
disease from mutations in PIGA enzyme essential for synthesis of MAC regulatory proteins
what is the only hemolytic anemia caused by acquired genetic defect
PNH
what are PNH blood cells deficient in
3 GPI-linked proteins that regulate C’ activity
CD55 CD59 and C8
what is inheritance of PNH
X linked
RBC in PNH are prone to what
injury by C’ or lysis
intravascular from MAC attack
typical presentation PNH
chronic hemolysis without dramatic Hburia
at night because blood pH drops at night which increases C’ activity
what is leading cause of deat in individuals with PNH
thrombosis
venous- hepatic or cerebral
what neoplasias are PNH assoc with
myelodysplastic syndrome and acute myeloid leukemia
What do we detect on flow cytometry for PNH
CD59
Tx for PNH
eculizumab to prevent conversion of C5 to C5a
reducing thrombosis by 90%
eculizumab increases risk for what
serious or fatal meningococal infections
what characterizes immunohemolytic annemias
Ab that bind to RBC leading to premature destruction
Describe warm Ab type immunohemolytic anemia
IgG
can be primary (idiopathic)
secondary (SLE) (drugs lymphoid neoplasms)
describe cold agglutinin type immunohemolytic anemia
IgM (active below 37C)
acute (mycoplasmal infection, infectious mononucleosis)
chronic: idiopathic, lymphoid neoplasms
describe cold hemolysin type immunohemolytic anemia
IgG active below 37
rare- children after viral infection
how do you Dx immunohemolytic anemia
direct Coombs antiglobulin test
what is indirect Coombs antiglobulin test used for
to charcterize the Ag target and temperature dependence of Ab
what is most common form immunohemolytic anemia
warm Ab type
types of drug induced warm hemolytic anemia
antigenic drugs that promote extravascular hemolysis by acting like opsonins
tolerance breaking drugs that create autoAb
example of tolerance breaking drug that can lead to autoAb against RBC
alpha methlydopa
clinical symptoms of cold agglutinin hemolytic anemia
pallor cyanosis and raynaud phenomenon
exposed areas like finger toes, nose etc
what is paroxysmal cold hemoglobinuria
rare disorder that can cause fatal intravascular hemolysis
type of cold hemolysin type hemolytic anemia
most significant hemolysis caused by trauma to rBC is seen in what individuals
cardiac valve prostheses and microangiopathic disorders
what is microangiopathic hemolytic anemia seen in
DIC TTP HUS malignant HTN SLE disseminated cancer
cause of RBC damage in microangiopathic disorders
luminal narrowing form fibrosis or other stuff causing damage to RBC
what do rBC look like after damage
schistocytes RBC fragments "burr cells" "helmet cells" "triangle cells"