5.4 Normocytic Anemias Flashcards
What is the key differential to make early on with normocytic anemias in terms of the cause?
Being an anemia, there are low levels of RBC’s for some reason
Must differentiate whether this is caused by increased peripheral destruction, or underproduction
Reticulocyte count is good way to differentiate between the two
What are reticulocytes and how are they identified?
They are young RBC’s released from the marrow
On smear: slightly larger than normal, bluish cytoplasm from residual RNA
What is a normal reticulocyte count?
1-2%
What happens to the reticulocyte count as a normal response to anemia?
Marrow should respond with an increase production raising the RC to more than 3%
How is the reticulocyte count falsely represented in anemia and how is it corrected?
RC is a measure of relative percent so having changes in overall RBC count will affect the count, and in anemia with falsely elevate the levels
To correct, multiple the RC by the Hct/45
This gives a relative percentage of Hct based on normal and provides a comparison for how the RC might have changed
How can the corrected reticulocyte count determine whether a normocytic anemia is caused by peripheral destruction or underproduction?
If the corrected value is greater than 3%, then the marrow is responding appropriately and indicates peripheral destruction
If under 3%, then indicates marrow is not functioning properly and is more likely an underproduction problem
What is extravascular hemolysis?
RBC destruction by the reticuloendothelial system which includes the macrophages of the spleen, liver, and lymph nodes
Describe the breakdown of particles and where they go in extravascular hemolysis
HB broken down to heme and globin Globin becomes amino acids Heme becomes iron and protoporphyrin Iron is recycled Protoporphyrin becomes unconjugated bilirubin which is bound to serum albumin and delivered to liver for conjugation and excretion in bile
Clinical and Lab findings of extravascular hemolysis
Anemia with splenomegaly, jaundice (unconjugated), increased risk of bilirubin gallstones
Marrow hyperplasia with corrected RC greater than 3%
What is haptoglobin?
Binds free Hb and takes it to the spleen for potential recycling
Low levels of haptoglobin is an early sign of intravascular hemolysis
Clinical and lab findings of intravascular hemolysis
Hemoglobinemia
Hemoglobinuria
Hemosiderinuria
Decreased haptoglobin
Explain why Hemosiderinuria is seen in intravascular hemolysis
As RBC’s lyse in the blood, Hb is released and is filtered in the kidney
Tubular cells pick up some of the Hb and break it down to iron which accumulates in the cells as hemosiderin
With time, the cells will slough off and cause hemosiderinuria
