Normocytic Anemia

Question 1

How is normocytic anemia characterized? What are the two general causes? What is used to distinguish between the two etiologies?

Answer 1

MCV 80-100 um^3, underproduction or peripheral destruction, reticulocyte count is used to distinguish between these etiologies

Question 2

What are reticulocytes? What is the normal reticulocyte count? How does bone marrow respond to anemia?

Answer 2

Young RBCs released from BM identified on blood smear as larger cells with bluish cytoplasm (residual RNA); 2%, By increasing RC to > 3%

Question 3

How is RC falsely elevated in anemia? How is it corrected for? How is the corrected RC interpreted?

Answer 3

Decreased number of RBCs compared to reticulocytes falsely elevates RC. It is corrected for by multiplying the RC by HCT/45%. If corrected RC >3% good marrow response, suggests peripheral destruction, RC < 3% indicates poor marrow response and suggests underproduction.

Question 4

How is peripheral RBC destruction (hemolysis) subcategorized? Describe the bone marrow response.

Answer 4

Into intravascular and extravascular hemolysis. Both have good bone marrow responses.

Question 5

Describe the mechanism of extravascular hemolysis and Hb breakdown.

Answer 5

RBC destruction by reticuloendothelial system (macrophages of spleen, liver, lymph nodes). Macros break down globin into AAs, Heme into iron and protoporphyrin (iron recycled), Protoporphyrin is broken down into unconjugated bilirubin, bound to serum albumin and transported to liver for conjugation and excretion.

Question 6

What are clinical laboratory findings of extravascular hemolysis?

Answer 6

Anemia w/ splenomegaly, jaundice from high serum levels of unconjugated bilirubin, and increased risk of bile stones from excess unconjugated bilirubin, BM hyperplasia w/ RC > 3%

Question 7

What is intravascular hemolysis?

Answer 7

Destruction of RBCs within vessels.

Question 8

What is the evolution of the clinical presentation of intravascular hemolysis leading to normocytic anemia?

Answer 8

1. Hemoglobinemia - Hb is bound by haptoglobin which attempts to salvage lost Hb, 2. Hemoglobinuria (Hb very water soluble) 3. Hemosiderinuria 4. Decreased serum haptoglobin

Question 9

Describe the mechanism leading to hemosiderinuria

Answer 9

Renal tubular cells reabsorb some Hb that is filtered and break it down into iron which accumulates as hemosiderin. tubular cells eventually slough off resulting in hemosiderinuria