Anaemia - Haemolytic Anaemia Flashcards
Outline the epidemiology of haemolytic anaemia (3).
- Most common form of autoimmune haemolytic anaemia
- Affects more women than men
- It may arise spontaneously or in association with diseases or drugs
- Diseases such as: Systemic lupus erythematosus / lymphoma / chronic lymphocytic leukaemia
- Drugs are a rare but well-described cause of haemolytic anaemia, estimated to occur in 1 in 1 million of the population
What are the risk factors of haemolytic anaemia (Hx 4 / Fx 1 / 2)?
Hx of:
* Autoimmune disorders
* Lymphoproliferative disorders
* Prosthetic heart valve
* Recent exposure to cephalosporins, penicillins, quinine derivatives, or non-steroidal anti-inflammatory drugs
* Recent exposure to naphthalene or fava beans
* Thermal injury
Fx of:
* Haemoglobinopathy or red blood cell membrane defects
Family origin in Mediterranean, Middle East, Africa or Southeast Asia
Paroxysmal nocturnal haemoglobinuria
Outline the pathogenesis of haemolytic anaemia (Hereditary 3 / Acquired 6).
Hereditary causes fall into three broad categories:
* Inherited red blood cell (RBC) defects (membrane defects) - hereditary spherocytosis, elliptocytosis, pyropoikilocytosis
* Enzyme deficiencies - glucose-6-phosphate dehydrogenase deficiency, pyruvate kinase deficiency
* Abnormal Hb production - sickle cell anaemia, thalassaemia
Acquired haemolytic anaemia can be subdivided into immune and non-immune aetiologies:
* Autoantibodies - the cause of immune-mediated haemolytic anaemias, most often as part of other autoimmune conditions (e.g., systemic lupus erythematosus, rheumatoid arthritis, scleroderma) or related to a lymphoproliferative disorder (non-Hodgkin’s lymphoma, chronic lymphocytic leukaemia)
* Immune haemolytic anaemias - divided into warm- or cold-reacting antibodies, depending on the temperature at which the antibody binds most avidly to the RBCs
* Alloimmune haemolytic anaemias - include haemolytic disease of the newborn or transfusion reaction
* Drugs - some through immune-mediated mechanisms and others through non-immune-mediated mechanisms
* Other non-immune-mediated causes - include infection, trauma in various forms (microangiopathic haemolysis such as disseminated intravascular coagulation, thrombotic thrombocytopenic purpura, haemolytic uraemic syndrome, malignant hypertension, eclampsia, HELLP syndrome [haemolysis, elevated liver enzymes, low platelet count] in pregnancy, mechanical prosthetic heart valves, march haemolysis, thermal injury, osmotic lysis), hypersplenism, and liver disease
* Paroxysmal nocturnal haemoglobinuria - a rare disorder resulting in an acquired RBC membrane defect and subsequent haemolysis
Outline the pathophysiology of haemolytic anaemia (3).
- Sections of the RBC membrane are removed by the reticuloendothelial cells, RBCs with a smaller surface area appear as spherocytes on the peripheral smear
- This also results in the release of RBC lactate dehydrogenase and haemoglobin (Hb) into the circulation, which can result in haemoglobinuria
- Free Hb is bound by haptoglobin, resulting in the decrease in haptoglobin that is observed in many cases of haemolytic anaemia
How would a patient with haemolytic anaemia present (7)?
Common:
* Presence of risk factors (Fx)
* Pallor
* Jaundice
* Splenomegaly
* Fatigue
* Shortness of breath
* Dizziness
Uncommon:
* Active infections
* Episodic dark urine (haemoglobinuria)
* Triggered by exposure to cold
What investigations are recommended in suspected haemolytic anaemia (7)?
- FBC
- Reticulocyte count
- Peripheral smear
- Serum bilirubin
- LDH
- Haptoglobin
- Urinalysis
What would is the diagnostic result of FBC in haemolytic anaemia?
- Hb
- MCHC
- MCV
- Platelet
- WBC count
- Hb: reduced
- MCHC: elevated
- MCV: normal
- Platelet and WBC count: usually normal (with concurrent viral infection may be reduced)
What would is the diagnostic result of reticulocyte count in haemolytic anaemia (3)?
- Increased reticulocyte percentage (>1.5%)
- Increased absolute reticulocyte count
- Increased reticulocyte index
What would is the diagnostic result of peripheral smear in haemolytic anaemia?
- Abnormal forms such as schistocytes, spherocytes, elliptocytes, spur cells, blister cells, bite cells, tear drops
What would is the diagnostic result of unconjugated (indirect) bilirubin in haemolytic anaemia?
- Elevated, but not >70 to 85 micromol/L (5 mg/dL) unless liver function is impaired
What would is the diagnostic result of LDH in haemolytic anaemia?
High
What would is the diagnostic result of haptoglobin in haemolytic anaemia?
Low
What would is the diagnostic result of urinalysis in haemolytic anaemia?
- Dipstick positive for blood, no red blood cells
What is the management of a patient with acquired haemolytic anaemia with direct antiglobulin test (Coombs’) positive (1 + 3)?
Removal of insult or treatment of underlying condition
Adjuvant:
* Supportive care
* Corticosteroid
* Rituximab
What is the management of a patient with acquired haemolytic anaemia with direct antiglobulin test (Coombs’) negative (1 + 1)?
Treatment of underlying condition
Adjuvant:
* Supportive care
