Normocytic Anemia II (IntraVascular Hemolysis)

G6PD Deficiency

Intravascular Hemolysis

X Linked Recessive

Defect in HMP shunt → which helps protect RBCs from oxidation

Found in 12% of male African Americans and in Mediterranean region

Symptoms of G6PD Deficiency Comes As A Result Of:

1. Infection

2. Ingestion of an oxidizing drug (antimalarial, sulfonamides)

3. Fava beans

Acute self-limited hemolytic anemia with hemoglobinemia and hemoglobinuria

Deficiency of G6PD Leads To

Reduced NADPH → Reduced Glutathione

→ RBC hemolysis

→ Hemoglobin denaturation

→ Heinz bodies (precipitates)

Recognize hematuria after starting drug - especially antimalarial (military)

What are the Variants of G6PD Deficiency

African variant: mild variant (mild reduction in half-life of G6PD) Mediterranean: severe variant (severe reduction in half-life)

Role of G6PD In Defense Against Oxidant Injury

Reduced G6PD makes cells susceptible to oxidative stress

RBCs are normally protected from H2O2 by Glutathione (antioxidant, which becomes oxidized)

H2O2 is one of the major oxidative stressors → Becomes water with Glutathione

Deficiency of G6PD → Low NADPH → Low Glutathione → Increased Oxidative Stress → Hemolysis

Presents as → hemoglobinuria and back pain hours after exposure to oxidative stress

Describe Heinz Bodies from G6PD Deficiency

Oxidative stress precipitates Hgb as Heinz bodies

(inclusions within red blood cells composed of denatured hemoglobin)

Used for screening: using special Heinz stain

Heinz bodies are removed (cut) from RBCs by macrophages → resulting in bite cells

What studies confirm of G6PD?

Measurement of enzyme levels (Performed ONLY weeks after hemolytic episode resolves, as the defective RBCs are already hemolyzed and what is left during the episode are the non- defective ones)

Bite Cells (G6PD Deficiency)

Effects of oxidant drug exposure (peripheral blood smear)

"Bite cells" - splenic macrophages remove the Heinz body inclusions

Paroxysmal Nocturnal Hemoglobinuria

Acquired defect in RBCs, WBCs, and platelets

Absent defense mechanism on the surface of the cells → Makes cells susceptible to destruction by complement

Mutation of PIG-A gene that codes for (GPI) anchor

Describe the mechanism of the GPI anchor protecting RBCs

Normally, the cell is protected by a surface factor DAF (CD55, CD59 and C8 protein) which is anchoring on the surface membrane by GPI

Normally DAF (CD55/CD59) - GPI linked proteins help inactivate complement

Deficiency of (DAF) - GPI (CD55/CD59) → increased complement lysis

Features of PNH

1. Complement activation occurs episodically, often at night → shallow breathing, increased CO2, mild respiratory acidosis

2. Hemolysis at night (lysis of RBCs, WBCs, and platelets) → dark urine in the morning due to hemoglobinuria

3. Hemosiderinuria is seen days after hemolysis → can cause pancytopenia

Also increase venous thrombosis

Tests for PNH

Coombs negative hemolytic anemia Ham’s test: complement induced hemolysis in acidified serum (in vitro)

CD55/CD59 Found on the surface of RBCs prevent what?

CD55/CD59 on surface of RBCs, Platelets, and leukocytes prevent complement lysis

Screening and Dx of PNH

Sucrose test to screen (sucrose activates complement)

Hams test → Serum acidification for confirmation

Lack of CD55/CD59 (DAF) → detection by flow cytometry

Complications of PNH

1. Iron deficiency anemia

2. Aplastic Anemia

3. Acute myeloid leukemia (AML) which develop in 10%

Main Cause of Death of PNH

Thrombosis of the hepatic, portal, or cerebral veins → due to release of products from the lysed platelets

Malaria

RBCs are part of the life cycle of Plasmodium and they rupture during the cycle causing intravascular hemolysis

(RBCs assume different morphologic changes during the cycle)

Spleen also destroys some infected RBCs causing mild extravascular hemolysis and splenomegaly

*KNOW WHAT IT LOOKS LIKE ON A BLOOD SMEAR*

What is the name of the parasite that causes malaria? What transmits malaria?

Plasmodium is the parasite causing Malaria, transmitted by female Anopheles mosquito

Hemolytic Disease of the Newborn - Erythroblastosis Fetalis

Maternal antibodies cross the placenta and react with fetal red cells

Need to have prior delivery with maternal exposure to fetal blood

→ Causes fetal hemolytic anemia

→ Causes maternal alloimmunization to fetal RBC antigens

Usually maternal antibodies to D antigen of Rh blood group

Mother usually type d and baby type D

How can ABO incompatibility cause Hemolytic Disease of Newborn

Mother group O → child A or B

Mother A → child B or AB

Mother B → child A or AB

Less severe than Rh cases (mild)

1. Fetal A and B antigens not well developed

2. Antigens are expressed on lots of other tissues to “absorb” antibodies

Hemolytic Disease of the Newborn can cause

Kernicterus = staining of basal ganglia and other CNS system structures with unconjugated bilirubin

Neurologic damage

Stillbirths

Hydrops fetalis = fetal heart failure with massive edema

How can you treat Hemolytic Disease of the Newborn

Give anti-D IgG antiserum (RhoGAM) to D negative mothers at 28 weeks and at delivery of D+ child

This removes fetal red blood cells from maternal circulation (through antibody removal) and prevents alloimmunization

Microangiopathic Hemolytic Anemia

Mechanical Destruction of RBCs

Damage or destruction of the RBCs as they pass through the circulation → leading to intravascular hemolysis

Damage from:

Microthrombi

Prosthetic heart valves

Aortic stenosis

DIC/TTP/HUS

The damage produces…

Schistocytes and helmet cells on blood smear

Decreased production of Normocytic Anemia can cause:

1. Aplastic anemia*

2. Myelophthisic*

3. Anemia of chronic disease

4. Renal Failure

1. Aplastic Anemia

Rare, serious bone marrow failure

HOW? → Suppression or injury to the hematopoietic stem cell

You'll find→ Hypocellular marrow, pancytopenia, and no abnormal cells in blood or bone marrow

What causes damage to hematopoietic stem cells?

*KNOW THESE*

1. Chemicals - Benzene

2. Viral infections – Parvovirus B19, EBV, HIV

3. Drugs→ Chloramphenicol, sulfas, antimalarial, chemotherapeutic

4. Autoimmune damage – cytotoxic T cells

5. Radiation

What would be the result of a biopsy with Aplastic Anemia?

Almost empty bone marrow with predominantly fat and few bone spicules

Etiology of Aplastic Anemia

*Don’t forget about drugs, drugs, drugs*

1. Parvovirus B19

2. Fanconi anemia

3. Fanconi syndrome

Parvovirus B19

Viral infection resolving in a week or two in normal individuals

Happens in the presence of preexisting marrow stress (Sickle cell anemia)

→ Infects the BM progenitor cells →ineffective erythropoiesis → severe anemia

Fanconi anemia

Rare genetic disease

Causes bone marrow failure → all cell types → aplastic anemia

Fanconi syndrome

Rare kidney disorder

Inadequate reabsorption in the proximal renal tubules of the kidney

Caused by congenital or acquired diseases → toxic heavy metals or adverse drug

Aplastic Anemia Morphology

Symptoms of Aplastic Anemia

Fatigue

Malaise

Pallor

Purpura

Mucosal bleeding

Petechiae

Infection

Low reticulocyte count

Increased EPO to try to compensate Pancytopenia – decreased all cell lines (RBC, WBC and platelets)

*Note: Aplastic crises is anemia (RBC) only*

Treatment of Aplastic Anemia

1. Cessation of causative drug

2. Treatment of chemical effect

3. Immunosuppression → Cases caused by activation of T cells with cytokines

4. Bone marrow transplant

Myelophthisic Anemia

Replacement of bone marrow space with non hematopoietic tissue

Myelophthisic Anemia Can Be Caused By

1. Cancer

2. Marrow fibrosis

Impairment of hematopoiesis → pancytopenia

What indications in blood smear can show Myelophthisic Anemia?

Tear drop cells in smear = bone marrow fibrosis Peripheral blood: small numbers of nucleated red cells and immature granulocyte precursors

Morphology of Myelophthisic Anemia

Red Cell Inclusions

1. Coarse basophilic stippling: persistent ribosomes. Indicates Pb poisoning

2. Heinz bodies: result from denatured hemoglobin → Can be seen in G6PD deficiency.

3. Howell Jolly bodies: are remnants of

nuclear chromatin. Indicates non functional / absent spleen (Sickle cell anemia/splenectomy)

4. Ring sideroblasts: have iron trapped abnormally in mitochondria forming a ring around nucleus → Seen in sideroblastic anemia (in the bone marrow).

Causes of Acquired Hemolytic Anemia

1. Infection

2. Drugs

3. Burns

4. Thrombotic microangiopathies

5. Hypersplenism

6. Vasculitis

7. Severe HTN