Haematology Flashcards
Deep vein thrombosis (DVT) and venous thromboembolism (VTE)
VTE = common, potentially fatal condition where a thrombus develops in the circulation
DVT = thrombus in deep vein, if embolises and travel to right heart to lungs = pulmonary embolism (PE)
If spetal defect, thrombus can enter left heart, systemic circulation and brain = large stroke
Risk factors for DVT/VTE
Virchow’s triad:
- Hypercoagulability: smoking, pregnancy, maliganancy, systemic lupus erythematosus, polycythaemia, thrombophilia, HRT (oestrogen)
- Vessel injury: recent surgery
- Venous stasis: immobility, long haul travel
Reccurent VTE = antiphospholipid syndrome, recurrent miscarriage. Dx = antiphospholipid antibodies
Clinical features of DVT
- Unilateral
- Calf/leg swelling
- Dilated superficial veins
- Tenderness over deep vein site
- Oedema
- Colour changes
Measure calf circumference 10cm under tibial tuberosity, > 3cm difference = significant
Ix DVT
Wells score to consider the likihood of DVT and informs next steps
- Likely = leg vein USS
- Unlikely: D-dimer, if positive leg vein USS
If USS, but Wells score high = repeat USS after 6 - 8 days
D-dimer levels = senesitive not specific and can be raised in pneumonia, malignancy, pregnancy, surgery etc.
Management of DVT
Initial:
- Immediate Tx dose apixaban/rivoxaban, alterative is LMWH
- Iliofemoral DVT = catheter-directed thrombolysis
Long-term:
- DOAC except severe renal impairment (creatinine clearance < 15ml/min), antiphospholipid syndrome(APLS) and pregnancy
- Warfarin - INR target 2 -3, 1st line in APLS)
- LMWH - 1st line in pregnancy
- Review after 3m in reversible cause, 3-6m active cancer, long-term if unprovoked, ercurrect or irreversible (e.g. thrombophilia)
Ix for unprovoked DVT
1st unprovoked DVT = PMH, bloods and examination for cancer
Start on anticoagulation
Consider testing for antiphospholipid syndrome (APLS antibodies) or hereditary thrombophilia (if 1st degree relative also has DVT/PE)
Sickle cell disease
Autosomal recessive condition affecting gene for beta-globin on chromosome 11, causes sickle shaped red blood cells > more fragile > haemolytic anaemia > sickle cell crises.
One abnormal copy = sickle-cell trait
Normal = HbA
Sickle cell disease = HbS
Newborn blood spot around 5 days old and high-risk pregnant women are offered testing
Complications of sickle cell disease
- Anaemia
- Increased risk of infection
- Chronic kidney disease
- Sickle cell crises - Acute Chest Syndrome
- Stroke
- Avascular necrosis in large joints such as the hip
- Pulmonary hypertension
- Gallstones
- Priapism (painful and persistent penile erections)
Sickle cell crisis
A number of acute exacerbations caused by sickle cell disease.
- Vaso-occlusive crisis
- Splenic sequestration crisis
- Aplastic crisis
- Acute chest syndrome
Triggers: dehydration, infection, stress or cold weather
Sickle cell disease: vaso-occlusive crisis (VOC)
AKA painful crisis, caused by sickle cells blocking cappillaries.
Pain and swelling in hands or feet most commonly, but can affect chest, back or other areas +/- fever.
Can cause priapsm, emergency treated by aspiring blood from penis
Sickle cell disease: splenic sequestration crisis
Sickle cells blocking + trapping blood flow within spleen > enlarged and painful spleen > severe anaemia and hypovolaemic shock.
Emergency, treat with blood transfusion and fluid resus for anaemia and shock
SSC > splenic infarction > hyposplenism > increased susceptibility to infections due to trapped bacteria. Splenectomy in recurrent cases
Sickle cell anaemia: aplastic crisis
Temporary absence of creation of new RBCs, triggered by infection with parovirus B19 > significant anaemia (aplastic anaemia)
Supportive tx with blood transfusions, usually resolves within a week.
Sickle cell anaemia: Acute Chest Syndrome
RBCs clog up vessels supplying lungs (triggered by e.g. VOC or infection)
Fever, SOB, chest pain and hypoxia
CXR - pulmonary infiltrates
Emergency, supportive tx + underlying cause:
- Analgesia
- Hydration (IV/oral),
- Abx or antivirals
- Blood transfusion (anaemia)
- Respiratory support (O2/non-invasive or mechanical ventilation)
Management of sickle cell disease
- Specialist MDT
- Avoid triggers
- Up-to-date vax
- Prophylatic abx e.g. penicilin V (phenoxymethylpenicilin)
- Hydrocarbamide (stimulates HbF)
- Crizanlizumab+
- Blood transfusion (severe anaemia)
- BM transplant (curative)
+ mAb targeting P-selection on endothelial cells of blood vessels and platelets, reduces RBC sticking to blood vessel walls = less VOC
Thalassaemia
Normal Hb = 2 alpha-globin and 2 beta-globin chains
Alpha Thalassaemia = defect in alpha-globin chains
Beta-Thalassaemia = defect in beta-globin chain
RBC more fragile > haemolytic anaemia > spleen filters, collects and removes destroyed RBC > splenomegaly
Alpha-thalassaemia
Genes for alpha-globin on chromosome 16.
Severity depends on type and number of genetic defects:
- Asymptomatic carrier
- Moderate anaemia (haemoglobin H disease) - Intrauterine death due to severe fetal anemia (alpha thalassaemia major)
Mx: monitoring, blood transfusion, splenectomy, bone marrow transplant (curative)
Beta-thalassaemia
Genes for beta-globin protein on chromosome 11.
Abnormal copies with some function or deletion genes with no function in the beta-globin:
- Thalassaemia minor
- Thalassaemia intermedia
- Thalassaemia major
Beta-thalassaemia: Thalassaemia Minor
- Thalassaemia Minor (thalassaemia trait): carrier of one copy of abnormal beta-globin gene.
- Microcytic anaemia > monitoring
Beta-thalassaemia: Thalassaemia Intermedia
- Thalassaemia Intermedia: two abnormal copies of the beta-globin gene; either two defective genes or one defective and one deletion gene.
- Microcytic anaemia, monitoring + occasional blood transfusions + iron chelation
Beta-thalassaemia: Thalassaemia Major
- ## Homozygous for the deletion gene, no function beta-globin genes.
- Severe anaemia and failure to thrive in early childhood
- Bone marrow expands to produce extra RBC to compensate for chronic anaemia > fractures + changes in apperance
- Mx: tregular transfusions, iron chelation and splenectomy, bone marrow transplant curative
Clinical features of thalassaemia
Depends on type, but generally:
- Fatigue
- Pallor
- Jaundice
- Gallstones
- Splenomegaly
- Poor growth and development
Investigations for thalassaemia
FBC = microcytic anaemia (low mean cell volume), raised ferritin = iron overload
Haemoglobin electrophoresis to confirm globin abnormalities + DNA testing
All pregnant women offered screening at booking
Thalassaemia: iron overload
Caused by:
- Increased iron absoprtion in GI tract
- Blood transfusions
Complications: liver cirrhosis, hypothyroidism, heart failure, diabetes, osteoporosis
Monitor serum ferritin, limit transfusion and iron clelation therapy
Pernicious anaemia
Causes vitamin B12 deficiency > macrocytic anaemia
Autoimmune condition where autoantibodies attack parietal cells or intrinsic factor > intrinsic factor deficiency + B12 not absorbed.
Other causes of low B12
- Insufficient dietary B12 (vegan)
- Meds that reduce B12 absorption (PPI and metformin)
