Flashcards in Haematology Deck (187)
What is aplastic anaemia?
Characterised by diminished haematopoietic precursors in the bone marrow and deficiency of all blood cell elements (pancytopaenia)
What is the aetiology of idiopathic aplastic anaemia?
May be due to destruction or suppression of the stem cell by autoimmune mechanisms
What is the aetiology of acquired anaplastic anaemia?
- Drugs (chloramphenicol, gold, alkylating agents, antiepileptics, sulphonamids, methotrexate, nifedipine)
- Chemicals (DDT, benzene)
- Viral infection (B19 parvovirus, HIV, EBV)
- Paroxysmal nocturnal haemoglobinuria
What is the aetiology of inherited aplastic anaemia?
- Fanconi's anaemia
- Dyskeratosis congenita (associated with reitculated hyperpigmented rash, nail dystrophy and mucosa leukoplakia)
What is the epdemiology of aplastic anaemia?
- Can occur at any age
- Slightly more common in males
What are the presenting symptoms of aplastic anaemia?
Slow (months) or rapid (days) onset
- Anaemia: Tiredness, lethargy, dyspnoea
- Thrombocytopaenia: Easy bruising, bleeding gums, epistaxis
- Leukopenia: Increased frequency and severity of infections
What are the signs of aplastic anaemia on examination?
- Anaemia: Pale
- Thrombocytopaenia: Petechiae, bruises
- Leukopenia: Multiple bacterial or fungal infections. No hepatomegaly, splenomegaly or lymphadenopathy
What are the investigations for aplastic anaemia?
- Blood: FBC (reduced Hb, platelets, WCC, normal MCV, low or absent reticulocytes)
- Blood film: Exclude leukaemia
- Bone marrow trephine biopsy:
- Criteria for severe aplastic anaemia (AA)
What is a blood transfusion?
Process of receiving blood or blood products into one's circulation intravenously
What are the indications for a blood transfusion?
- Major surgical operation
- Accidents resulting in considerable blood loss
- Cancer pts requiring therapy
- Severe burn victims
- Pts of hereditary disorders like Haemophilia and Thalassaemia
What are the possible complications of blood transfusions?
- Acute haemolytic reactions
- Delayed haemolytic reactions
- Febrile nonhaemolytic reactions
- Tranfusion-associated acute lung injury
What is disseminated intravascular coagulation (DIC)?
Disorder of the clotting cascade that can complicate a serious illness. May occur in 2 forms:
1) Acute overt form where there is bleeding and depletion of platelets and clotting factors
2) Chronic non-overt form where thromboembolism is accompanies by generalised activation of the coagulation system
What is the aetiology of DIC?
- Infection: Particularly Gram-negative sepsis
- Obstetric complications: Missed miscarriage, severe pre-eclampsia, placental abruption, amniotic emboli
- Malignancy: Acute promyelocytic leukaemia (acute DIC), lung, breast, GI, malignancy (chronic DIC
- Also haemolytic transfusion reaction, burns, severe liver disease , aortic aneurysms, haemangiomas
What is the aetiology of acute DIC?
- Activation of coagulation is a consequence of endothelial damage and increased release of granulocyte/macrophage procoagulant substances e.g. tissue factor
- Explosive thrombin generation depletes clotting factors and platelets while simultaneously activating the fibrinolytic system
- Leads to bleeding in subcutaneous tissues, skin and mucous membranes
- Occlusion of blood vessels by fibrin results in microangiopathic haemolytic anaemia and ischaemic organ dammage
What is the epidemiology of DIC?
Seen in any severely ill patient
What are the presenting symptoms of DIC?
If pt is severely unwell with symptoms of the underlying disease, confusion, dyspnoea and evidence of bleeding
What are the signs of DIC on examination?
Signs of underlying aetiology, fever, evidence of shock (hypotension, tachycardia)
- Acute DIC: Petechiae, purpura, echhymoses, epistaxis, mucosal bleeding, over haemorrhage. Signs of end organ damage (e.g. local infarction or gangrene), respiratory distress, oliguria caused by renal failure
- Chronic DIC: Signs of deep venous or arterial thrombosis or embolism, superficial venous thrombosis, especially without varicose veins
What are the investigations for DIC?
- Blood: FBC (reduced platelets, Hb. Clotting: Increased APTT/PT/TT, fibrin degradation products and d-dimers, reduced fibrinogen)
- Peripheral blood film: Red blood cell fragments (schistocytes). Other investigations according to aetiology
What is haemochromatosis?
Body iron overload resulting from excessive intestinal iron absorption which may lead to organ damage (particular liver, joints, pancreas, pituitary and heart)
What is the aetiology of haemochromatosis?
- Mutation in the HFE gene on chromsome 6p
- Most common mutation is C282Y, less common is H63D
What is the epidemiology of haemochromatosis?
- Carrier frequency is up to 1/10, not all express disease
- Age of presentation = 40-60 yrs typically
- Females have later onset and less severe presentation as a result of iron loss through menstruation
What are the presenting symptoms of haemochromatosis?
- May be asymptomatic
- Non specific symptoms: weakness, fatigue, lethargy and abdo pain
- Later features: small/large joint pains (most commonly 2nd/3rd MCP joints), symptoms of liver disease, DM, hypogonadism, cardiac failure
- Exclude causes of secondary iron overload (e.g. multiple transfusions)
What are the signs of haemochromatosis on examination?
May be normal, but with severe iron overload:
- Skin: Pigmentation ('slate-grey) resulting from increased melanin deposits
- Liver: Hepatosplenomegaly
- Heart: Signs of heart failure, arrhythmias
- Hypogonadism: Testicular atrophy, loss of hair, gynaecomastia
What are the investigations for haemochromatosis?
- Blood: Increased iron, ferritin and transferrin sats, reduced TIBC
- Gene typing of HFE
- Test for complications in various organs, LFTs, fasting or random blood glucose, pituitary function test, ECG, Joint X-ray
What is haemolytic anaemia?
Premature erythrocyte breakdown causing shortened erythrocyte life span (less than 120 days) and anaemia
What is the aetiology of hereditary haemolytic anaemia?
- Membrane defects: Hereditary spherocytosis, elliptocytosis
- Metabolic defects: G6PD deficiency. Pyruvate kinase deficiencies (autosomal recessive)
- Haemoglobinopathies: Sickle cell disease, thalassaemia
What is the aetiology of acquired haemolytic anaemia?
- Autoimmune: Warm or cold antibodies attach to erythrocytes causing intravascular haemolysis and extravascular haemolysis
- Isoimmune: Transfusion reaction, haemolytic disease of the newborn
- Drugs: Penicillin, quinine
- Trauma: Microangiopathic haemolytic anaemia caused by red cell fragmentation in abnormal microcirculation (haemolytic uraemic syndrome, DIC, pre-eclampsia), artificial heart valves
- Infection: Malaria, sepsis
- Paroxysmal nocturnal haemoglobinuria
What is the epidemiology of haemolytic anaemia?
- Genetic causes prevalent in African, Mediterranean, Middle Eastern populations
- Hereditary spherocytosis is most common inherited haemolytic anaemia in Northern Europe
What are the presenting symptoms of haemolytic anaemia?
- Ask about systemic illness, family, drug and travel history