Hemolytic Anemia Types and Causes

Definition and Classification

• Hemolytic anemia is a type of anemia characterized by the premature destruction of red blood cells (RBCs)
• Classified into two main categories:
  • Intrinsic hemolytic anemia: defects within the RBCs themselves
  • Extrinsic hemolytic anemia: destruction of RBCs due to external factors

Causes of Intrinsic Hemolytic Anemia

• Genetic defects:
  • Hereditary spherocytosis: abnormal RBC shape and membrane structure
  • Hereditary elliptocytosis: abnormal RBC shape
  • Pyruvate kinase deficiency: enzyme deficiency affecting RBC energy metabolism
• Acquired defects:
  • Paroxysmal nocturnal hemoglobinuria (PNH): abnormal RBC membrane protein
  • G6PD deficiency: enzyme deficiency affecting RBC antioxidant defenses

Causes of Extrinsic Hemolytic Anemia

• Autoimmune hemolytic anemia (AIHA): production of antibodies against RBCs
  • Warm AIHA: IgG antibodies bind to RBCs at body temperature
  • Cold AIHA: IgM antibodies bind to RBCs at low temperatures
• Infections:
  • Malaria: parasite infection and destruction of RBCs
  • Babesiosis: parasite infection and destruction of RBCs
• Mechanical trauma:
  • Microangiopathic hemolytic anemia: RBC destruction due to abnormal blood flow and small vessel obstruction
• Toxicity:
  • Snake venom: hemolytic toxins in some snake venoms
  • Chemicals: certain chemicals, such as lead, can cause RBC destruction

Clinical Features and Diagnosis

• Symptoms: fatigue, weakness, pale skin, jaundice, dark urine
• Laboratory findings:
  • Anemia: low RBC count, hemoglobin, and hematocrit
  • Reticulocytosis: increased immature RBCs
  • Bilirubinemia: increased bilirubin levels
  • Direct Coombs' test: detects antibodies bound to RBCs
• Diagnostic tests:
  • Blood smear: examination of RBC morphology
  • Bone marrow biopsy: examination of bone marrow cellularity and morphology

Treatment and Management

• Treatment depends on the underlying cause
• Supportive care:
  • Blood transfusions
  • Folic acid supplementation
• Immunotherapy:
  • Corticosteroids
  • Rituximab (for AIHA)
• Splenectomy: surgical removal of the spleen (for hereditary spherocytosis and other forms of hemolytic anemia)

Definition and Classification

• Hemolytic anemia is characterized by the premature destruction of red blood cells (RBCs)
• Classified into two main categories: intrinsic and extrinsic hemolytic anemia

Intrinsic Hemolytic Anemia

• Caused by genetic defects, such as:
  • Hereditary spherocytosis: abnormal RBC shape and membrane structure
  • Hereditary elliptocytosis: abnormal RBC shape
  • Pyruvate kinase deficiency: enzyme deficiency affecting RBC energy metabolism
• Caused by acquired defects, such as:
  • Paroxysmal nocturnal hemoglobinuria (PNH): abnormal RBC membrane protein
  • G6PD deficiency: enzyme deficiency affecting RBC antioxidant defenses

Extrinsic Hemolytic Anemia

• Caused by autoimmune hemolytic anemia (AIHA), including:
  • Warm AIHA: IgG antibodies bind to RBCs at body temperature
  • Cold AIHA: IgM antibodies bind to RBCs at low temperatures
• Caused by infections, such as:
  • Malaria: parasite infection and destruction of RBCs
  • Babesiosis: parasite infection and destruction of RBCs
• Caused by mechanical trauma, such as:
  • Microangiopathic hemolytic anemia: RBC destruction due to abnormal blood flow and small vessel obstruction
• Caused by toxicity, such as:
  • Snake venom: hemolytic toxins in some snake venoms
  • Chemicals: certain chemicals, such as lead, can cause RBC destruction

Clinical Features and Diagnosis

• Symptoms: fatigue, weakness, pale skin, jaundice, and dark urine
• Laboratory findings, including:
  • Anemia: low RBC count, hemoglobin, and hematocrit
  • Reticulocytosis: increased immature RBCs
  • Bilirubinemia: increased bilirubin levels
  • Direct Coombs' test: detects antibodies bound to RBCs
• Diagnostic tests, including:
  • Blood smear: examination of RBC morphology
  • Bone marrow biopsy: examination of bone marrow cellularity and morphology

Treatment and Management

• Treatment depends on the underlying cause
• Supportive care, including:
  • Blood transfusions
  • Folic acid supplementation
• Immunotherapy, including:
  • Corticosteroids
  • Rituximab (for AIHA)
• Surgical intervention, including:
  • Splenectomy: surgical removal of the spleen (for hereditary spherocytosis and other forms of hemolytic anemia)