Haematology Flashcards
Describe the changes in Hb levels from birth
- The Hb concentration is high at birth (>140 g/L)
- Hb levels fall to the lowest level at around 2 months of age (about 100 g/L)
What is the definition of anaemia?
Anaemia is defined as an Hb level below the normal range. The normal range varies with age, so anaemia can be defined as:
- Neonate: Hb < 140 g/L
- 1 month to 1 year: Hb < 100 g/L
- 1 year to 12 years: Hb < 110 g/L
How can the causes of anaemia be categorised?
- Reduced red cell production
- Increased red cell destruction (haemolysis)
- Blood loss (uncommon in children)
Describe the different mechanisms of reduced red cell production
- Ineffective erythropoiesis (e.g. iron deficiency, the most common cause of anaemia)
- Red cell aplasia: complete absence of red cell production
What are the causes of iron deficiency anaemia?
- Inadequate intake of iron (common)
- Malabsorption
Why might an infant/child have inadequate intake of iron?
- Delay in introduction of mixed feeding beyond 6 months of age
- Diet with insufficient iron-rich foods
- Infants should not be fed unmodified cow’s milk as its iron content is low and poorly absorbed
Describe the clinical presentation of iron deficiency anaemia
- Pallor
- Lethargy
- Some children exhibit ‘pica’ - inappropriate eating of non-food materials
Describe the investigation of iron deficiency anaemia
FBC:
- Microcytic anaemia
- Low serum ferritin
Describe the management of iron deficiency anaemia
- Dietary advice
- Supplementation with oral iron
What is haemolytic anaemia?
Reduced red blood cell lifespan/premature destruction of RBCs
How can the causes of haemolytic anaemia be classified?
- Red cell membrane disorders, e.g. hereditary spherocytosis
- Red cell enzyme disorders, e.g. G6PD deficiency
- Haemoglobinopathies, e.g. sickle cell disease, thalassaemia
Describe the epidemiology of sickle cell disease
More common in patients of black African/Caribbean descent
Describe the pathophysiology of sickle cell disease
Sickle cell disease is caused by defective Hb
- In normal physiology, adult Hb is made up of two alpha-globin chains and two beta-globin chains
- In sickle cell disease, there is a mutation in the beta-globin gene, which causes RBCs to become misshapen (sickled) when deoxygenated
- This results in damage to red blood cell membranes and premature destruction (haemolytic anaemia)
Describe the inheritance of sickle cell disease
Autosomal recessive
What evolutionary advantage do sickle cell carriers have?
Decreased severity of Plasmodium falciparum malaria
Describe the clinical presentation of sickle cell disease
- Anaemia (pallor, lethargy)
- Increased susceptibility to infection (due to hyposplenism, secondary to chronic sickling and microinfarction of the spleen)
- Painful, vaso-occlusive crises, e.g. dactylitis, avascular necrosis of bone, acute chest syndrome
Describe the investigation of sickle cell disease
- Newborn screening (heel-prick test)
- FBC: raised reticulocyte count
- Blood film: sickled erythrocytes
- Hb electrophoresis
Describe the conservative, pharmacological and interventional management of sickle cell disease
Conservative:
- Vaso-occlusive crises minimised by avoiding exposure to cold, dehydration, hypoxia, excessive stress/exercise
Pharmacological:
- Immunisation and prophylactic antibiotics
- Folic acid (increased demand)
- Acute, painful crises managed with analgesia, fluids and oxygen
- Disease modifying treatment: hydroxycarbamide
Interventional:
- Bone marrow transplant
Describe the pathophysiology of beta thalassaemia
Beta thalassaemia is caused by defective Hb
- In normal physiology, adult haemoglobin is made up of two alpha-globin chains and two beta-globin chains
- In beta thalassaemia, there is a mutation in the beta-globin gene, which results in reduced or absent beta-globin chain synthesis
- This results in damage to red blood cell membranes and premature destruction (haemolytic anaemia)
Describe the inheritance of beta thalassaemia
Autosomal recessive
Describe the investigation of beta thalassaemia
- FBC: raised reticulocyte count
- Blood film: microcytic, hypochromic RBCs
- Hb electrophoresis
Describe the management of beta thalassaemia minor, intermedia and major
Beta thalassaemia minor does not usually require treatment
Beta thalassaemia major (and sometimes intermedia):
- Regular blood transfusions
What needs to be considered in a patient receiving regular blood transfusions?
- Risk of iron overload and deposit in major/endocrine organs, e.g. liver, heart, pancreas
- Therefore, iron chelation agents are given, e.g. deferoxamine, penicillamine
What are the different types of haemophilia?
- Haemophilia A (factor XIII deficiency) is most common
- Haemophilia B (factor IX deficiency)
Describe the inheritance of haemophilia
X-linked recessive
Describe the management of haemophilia
- Haemophilia A: recombinant factor XIII concentrate
- Haemophilia B: recombinant factor IX concentrate
Describe the pathophysiology of von Willebrand’s disease
Quantitative/qualitative deficiency in vWF, resulting in defective platelet plug formation
Describe the inheritance of von Willebrand’s disease
Autosomal dominant
What is the definition of thrombocytopenia?
Platelet count <150 x 10^9/L
Describe the classification of thrombocytopenia
- Severe: <20 x 10^9/L
- Moderate: 20-50 x 10^9/L
- Mild: 50-150 x 10^9/L
Describe the clinical presentation of thrombocytopenia
- Bruising
- Petechiae
- Purpura
- Excessive, prolonged bleeding (particularly mucosal bleeding, e.g. epistaxis, menorrhagia)
What is the most common cause of thrombocytopenia?
Describe its pathophysiology
- Immune thrombocytopenic purpura (ITP)
- Caused by destruction of platelets by IgG antibodies
- Usually occurs following viral infection
Describe the prognosis and management of ITP
- Self-limiting
- Doesn’t usually require treatment
Which type of leukaemia is most common in childhood?
Acute lymphoblastic leukaemia (ALL)
Describe the clinical presentation of ALL
- Usually present 2-5 years
- In most children, ALL presents insidiously over several weeks, e.g. malaise, anorexia
- Signs of bone marrow infiltration:
Anaemia - pallor, lethargy
Neutropenia - increased susceptibility to infection
Thrombocytopenia - bruising, bleeding (e.g. epistaxis), petechiae
Bone pain - Other signs:
Hepatosplenomegaly
Lymphadenopathy
Describe the investigation of ALL
- FBC - anaemia, neutropenia, thrombocytopenia
- Blood film - blast cells
- Bone marrow biopsy is diagnostic
Describe the management of ALL
- Anaemia - blood transfusion
- Thrombocytopenia - platelet transfusion
- Neutropenia - treat any infection
- Chemotherapy and steroids
