anemias Flashcards
what are anemias?
reduction of the total circulating red blood cell mass below normal limits => tissue hypoxia
what changes would you see in cell morphology as a result of anemia?
RBC size
degree of hemoglobinization (reflected in color of RBCs)
shape
what is the difference between microcytic hypochromic anemia and macrocytic anemia?
micro = disorders of Hb synthesis (usually iron deficiency)
macro = due to abnormalities that impair maturation of erythroid precursors in bone marrow
what are the cell indicies of anemia?
1: mean cell volume
2: mean cell Hb
3: mean cell Hb concentration
4: RBC distribution width
what are the features of hemolytic anemias?
1: premature destruction of red cells and a shortened red cell life span below the normal 120 days
2: elevated erythropoietin levels and a compensatory increase in erythropoiesis
3: accumulation of hemoglobin degradation products released by red cell breakdown derived from Hb
what is extravascular hemolysis? what is it caused by? what are the clinical features?
premature destruction of RBCs within phagocytes
due to alterations that render RBC less deformable
clinical features = anemia, splenomegaly, jaundice
what causes intravascular hemolysis? what are the consequences?
mechanical injury, complement fixation, intracellular parasites, exogenous toxic factors
manifested by: anemia hemoglobinemia hemoglobinuria hemosiderinuria jaundice
what are the morphological changes of anemia?
increased production of erythropoietin => erythroid differentiation => increased numbers of erythroid precursors in marrow
compensatory increases in erythropoiesis => reticulocytosis in peripheral blood
what is hereditary spherocytosis (HS)?
inherited disorder caused by intrinsic defects in RBC membrane skeleton that render RBCs spheroid, less deformable, and vulnerable to splenic sequestration and destruction
usually autosomal dominant - otherwise due to inheritance of two different defects
results in decreased lifespan of RBCs to 10-20 days - reduced stability of the lipid bilayer => loss of membrane fragments as red cells age in the circulation
what does spherocytosis look like?
on smears - abnormally small, dark-staining red cells lacking the central zone of pallor
what does HS morphologically look like?
spherocytosis reticulocytosis marrow erythroid hyperplasia hemosiderosis mild jaundice cholelithiasis (pigment stones)
what are aplastic crises? what triggers them?
crisis in patients with chronic hemolytic anemia of mild to moderate severity
usually triggered by parvovirus infection - kills RBC progenitors
what are hemolytic crises?
in patients with anemia
produced by intercurrent events leading to increased splenic destruction of red cells
what is the consequence of glucose-6-phosphate dehydrogenase deficiency?
abnormalities in hexose monophosphate shunt or glutathione metabolism resulting from deficient or impaired enzyme function reduce ability of RBCs to protect themselves against oxidative injuries and lead to hemolysis
normally, G6PD reduces NADP to NADPH while oxidizing glucose-6-phos
NAPDH provides reducing equivalents needed for conversion of oxidized glutathione to reduced glutathione - protects against oxidant injury
mutation causes misfolding of the protein - more susceptible to proteolytic degradation
get episodic hemolysis when there are exposures that generate oxidant stress - usually infections - free radicals produced by leukocytes
what are heinz bodies? what happens to them (ie how are they removed) and what are the consequences for the cells?
when G6PD-deficient RBCs exposed to oxidants - reactive sulfhydryl groups cross-link on globin chains - become denatured and make membrane-bound precipitates
seen as dark inclusions within RBCs stained with crystal violet
macrophages in spleen “pluck out” the heinz bodies, but if the cells have membrane damage, can retain abnormal shape - cells will appear to have a bite taken out of them
