- hematology home
- immunology home
- signs and symptoms
- investigations
- conditions and diseases
Section Links
Hemolytic Anemia
- epidemiology
- types of hemolytic anemia
- signs and symptoms
- diagnosis
- pathophysiology
- causes and risk factors
- treatments
- course
- patient education
- community resources
- references
Epidemiology
Types of Hemolytic Anemia
Hemolysis is an increased rate of RBC destruction, and can result in hemolytic anemia if destruction exceed production.
RBC defects
can occur due to problems with RBC membranes, enzymes, or hemoglobin.
- heriditary spherocytosis can occur due to mutations in the cytoskeletal protein ankyrin, leading to increased splenic clearance and mild-moderate anemia
- hereditary elliptocytosis is autosomal dominant. Heterozygotes are ok, but homozygous mutations can cause life-threatening anemia
- G6PD deficiency
- thalassemias
- sickle cell anemia
Immune-mediated hemolytic anemia
spherocytes are seen on peripheral smears.
- idiopathic
- drug-induced
- neoplastic
- infections
- auto-immune
warm agglutinins: IgG
- diagnose via spherocytes and the direct antiglobulin test (DAT)
- cleared by splenic macrophages
cold agglutinins: IgM
- RBCs directly lysed or cleared following C3 coating
- diagnose with cold agglutination or the DAT (for C3)
fragmented RBCs
Microangiopathic hemolytic anemia
- disseminated intravascular coagulation (DIC)
- throbotic thrombocytopenic purpura (TTP)
- hemolytic uremic syndrome (HUS)
- HELLP syndrome - hemolysis, elevevated liver enzymes, low platelets
- also malignant hypertension
- hemodynamic turbulence (ie heart valves)
- mechanical trauma (ie hedge trimmers)
Signs and Symptoms
- Jaundice from extravascular anemia
- symptoms of anemia
Diagnosis
- normocytic anemia can be present
- reticulocytosis
- increased LDH, an enzyme abundant in RBCs
- increased unconjugated bilirubin
intravascular hemolysis can lead to these further findings:
- decreased haptoglobin (will go down as the hemoglobin is bound, but is also an acute phase reactant and so will go up)
- hemoglobinuria
- hemosiderinuria
- free hemoglobin
peripheral smear
Pathophysiology
Extravascular hemolysis
Extravascular hemolysis occurs outside the vessels, and accounts for 90% of hemolytic events. Macrophages of the reticuloendothelial system, especially the spleen, are usually involved.
Hemoglobin is degraded, rather than being released into the circulation. Hemoglobin splits into CO2, iron, which is reutilized, and biliverdin, which is transformed into unconjugated bilirubin and released into the plasma.
Intravascular hemolysis
Intravascular hemolysis occurs within the vessels.
It usually results from damage to the RBC membrane. Free hemoglobin is released into the circulation, where it breaks down into alpha-beta dimers. This can cause hemoglobinuria or hemosiderinuria.
Free hemoglobin can also bind haptoglobin, a protein with high affinity for free Hgb. This mops up free Hgb and transports it to the liver for removal. Intravascular hemolysis thus can lead to decreased or absent haptoglobin.
Causes and Risk Factors
Treatments
Course