Haematology Flashcards
Disseminated intravascular coagulation
Pathophysiology
- Hemostasis goes out of control
- Various blood clots form –> organ ischaemia (kidneys, liver, lungs, brain)
- These clots consume platelets and clotting factors
- Therefore the rest of the blood is low on these factors
- Fibrin degradation products in the circulation (from breakdown of the clots) also interferes with new clot formation
- Therefore resulting in bleeding with even the slightest damage to vessel walls
= Bleeding and clotting
Disseminated intravascular coagulation
Investigations
- Decreased platelets
- Decreased fibrinogen
- Prolonged prothrombin time (PT)
- Prolonged activated partial thromboplastin time (APTT)
PT and PTT reflect low circulating coagulation factors - Elevated D-Dimer (fibrin degradation product)
- Schistocytes due to microangiopathic haemolytic anaemia
Disseminated intravascular coagulation
When might you see chronic DIC
- Solid tumours
- Large aortic aneurysms
Disseminated intravascular coagulation
What would you see on investigations
- Relatively normall findings due to compensation
Disseminated intravascular coagulation
Management
Focus on underlying cause
- Support underlying organs (ventilator, haemodynamic support, tranfusions if needed)
Disseminated intravascular coagulation
Causes
- Sepsis
- Trauma
- Obstetric complications, e.g. HELLP syndrome, amniotic fluid embolism
- Malignancy
Can all initially tip the balance in favour of clotting –> starting the process of DIC
Haemophilia
Pathophysiology
- Deficiency of clotting factors
- Leading to bleeding
Haemophilia
Inheritance
X-linked recessive
- All of the X chromosomes need to have the abnormal gene
- Men only require one abnormal copy as they only have one X chromosome
- Women require two abnormal copies
- If they only have one copy –> carrier
- Almost exclusively affects males as for a female to be affected it would require an affected father and an affected/carrier mother
Haemophilia
Features
- Excessive bleeding in response to minor trauma
- Risk of spontaneous hemorrhage
- Haemoarthroses (bleeding into joints)
- Haematomas
- Prolonged bleeding after trauma/surgery
- Cord bleeding in neonates
- Bleeding of gums, GI tract, UT (haematuria), retroperitoneal space, intracranial
KEY presentation of severe disease = spontaneous bleeding into joints and muscles
Haemophilia
Investigations
- Prolonged APTT
- Bleeding time, thrombin time and prothrombin time all normal
- Genetic testing
Haemophilia
Management
Prophylactically:
- Replace clotting factors via IV
- Complication = formation of antibodies against the clotting factor, making it ineffective Tx
Acutely:
- Infusions of affected factor (VIII or IX)
- Desmopressin to stimulate release of von Willebrand factor
- Antifibrinolytics, e.g. tranexamic acid
Haemophilia
Types
- Type A = deficiency in factor VIII
- Type B = deficiency in factor IX (Christmas disease)
Hyposplenism
Causes
- Splenectomy
- Sickle-cell
- Coeliac disease, dermatitis herpetiformis
- Graves’ disease
- Systemic lupus erythematosus
- Amyloid
Hyposplenism
Features on blood film
- Howell-Jolly bodies
- Siderocytes
Splenectomy
Post-splenectomy risks
- Pneumococcus
- Haemophilus
- Meningococcus
- Capnocytophaga canimorsus (dog bites)
Splenectomy
Vaccination
If elective, should be done 2 weeks prior to operation:
- Haemophilus influenza Type B (HiB)
- Meningitis A&C
Also:
- Annual influenza
- Pneumococcal every 5 years
Splenectomy
Antibiotic prophylaxis
- Penicillin V for at least 2 years or until 16 yrs old
- Can sometimes be for life
Splenectomy
Indications
- Trauma (1/4 = iatrogenic)
- Spontanous rupture (EBV)
- Hypersplenism (hereditaory sphero/elliptocytosis)
- Malignancy (lymphoma, leukaemia)
- Splenic cysts, hydatid cysts, splenic abscesses
Splenectomy
Complications
- Haemorrhage - from SHORT GASTRIC or SPLENIC HILAR vessels
- Pancreatic fistula (from iatrogenic damage to tail)
- Thrombocytosis - prophylactic aspirin
- Encapsulated bacteria infection (strep pneumo, haem influenza, Neisseria meningitidis)
Splenectomy
Post-splenectomy changes
- Platelets will rise first
- Blood film will change after following weeks
- Howell-Jolly bodies will appear on the film
- May also see target cells, pappenheimer bodies
- Increased risk of post-splenectomy sepsis -> prophylactic Abx and pneumococcal vaccine
Splenectomy
Post-splenectomy sepsis
- Typically occur with encapsulated organisms
- Risk is greatest in < 16 yrs and > 50 yrs
- Tx = Penicillin V 500 mg BD and Amoxicillin 250 mg BD
Splenectomy
Travel
- Asplenic individuals travelling to malaria endemic areas are at high risk and should have both pharmacological and mechanical protection
Myeloproliferative disorders
Umbrella term for what?
- Primary myelofibrosis
- Polycythaemia vera
- Essential thrombocythaemia
Myeloproliferative disorders
Pathophysiology
- Uncontrolled proliferation of a single type of stem cell
- Considered a type of bone marrow cancer
Myeloproliferative disorders
Cell lines and diseases
- Primary myelofibrosis = fibroblasts (monocytes, eosinophils, neutrophils, basophils)
- Polycythemia vera = erythrocytes (RBCs)
- Essential thrombocythaemia = megakaryocytes (platelets)
Myeloproliferative disorders
Complications
Have the potential to progress and transform into acute myeloid leukemia (AML)
Myeloproliferative disorders
Associated mutations
- JAK2
- MPL
- CALR
Myelofibrosis
Pathophysiology
- Can be the result of primary myelofibrosis, polycythemia vera or essential thrombocytopenia
- Proliferation of haematopoietic stem cell
- Resultant release of platelet-derived growth factors –> stimulates fibroblast growth factor
- Leads to fibrosis of the bone marrow, replaced by scar tissue
- Can lead to low production of blood cells –> anaemia and leukopenia
- Haematopoiesis starts occurring in liver and spleen (extramedullary haematopoiesis)
- Can lead to hepatosplenomegaly and portal hypertension
- If this occurs around the spine it can result in spinal cord compression
Myelofibrosis
Features
- Symptoms of anaemia
- Massive splenomegaly
- Hypermetabolic symptoms - weight loss, night sweats
Myelofibrosis
Investigations
- Anaemia
- High WBC and platelet count in early disease
- May be low in later disease
- High urate and LDH (increased cell turnover)
Blood film:
- TEARDROP POIKILOCYTES
- Poikilocytosis (varying sizes)
- Immature red and white cells (blasts)
Bone marrow biopsy:
- Usually ‘dry’ as it has turned to scar tissue
- Therefore, need trephine biopsy
- Genetic testing: JAK2, MPL and CALR
Myelofibrosis
Management
- Allogenic stem cell transplantation (potentially curative but carries risks)
- Chemotherapy (improves symptoms and slow progression but not curative)
- Supportive management of anaemia, splenomegaly, portal HTN
Polycythaemia vera
Pathophysiology
- Clonal proliferation of a marrow stem cell, erythroid cells
- Leads to an increased in red cell volume
- Often accompanied by overproduction of neutrophils and platelets
- INcidence peaks in 6th decade
Polycythaemia vera
Features
- Hyperviscosity
- Pruritus, typically after a hot bath
- Splenomegaly
- Haemorrhage (secondary to abnormal platelet function)
- Plethoric appearance
- Conjunctival plethora
- Hypertension in a third of patients
- Low ESR
- Ruddy complexion
Polycythaemia vera
Investigations
- FBC: raised haematocrit, neutrophils, basophils, platelets (in 1/2), raised red cell mass
- JAK2 mutation (92%)
- Serum ferritin
- Renal and liver function test
- Low ESR
- Raised leukocyte alkaline phosphate
Polycythaemia vera
Management
- Venesection to keep Hb in normal range = 1st line
- Aspirin to reduce risk of blood clots
- Chemo to control disease (hydroxyurea or phosphorus-32)
Polycythaemia vera
JAK-2 positive diagnostic criteria
Requires both
- High haematrocrit (> 0.52 in men, > 0.48 in women) OR raised red cell mass (> 25% above predicted)
- Mutation in JAK2
Polycythaemia vera
JAK-2 negative diagnostic criteria
Requires A1 + A2 + A3 + either another A or two B criteria
A1: Raised red cell mass (>25% above predicted) OR haematocrit >0.60 in men, >0.56 in women
A2: Absence of JAK2 mutation
A3: No cause of secondary erythrocytosis
A4: Palpable splenomegaly
A5: Presence of aquired genetic abnormality (excluding BRC-ABL) in haemopoietic cell
B1: Thrombocytosis (platelets > 450)
B2: Neutrophils > 10 in non-smokers, >12.5 in smokers
B3: Radiological evidence of splenomegaly
B4: Endogenous erythroid colonies or low serum erythropoietin
Essential thrombocytosis
Pathophysiology
- Essential thrombocytosis is one of the myeloproliferative disorders which overlaps with chronic myeloid leukaemia, polycythaemia rubra vera and myelofibrosis.
- Megakaryocyte proliferation results in an overproduction of platelets.
Essential Thrombocytosis
Features
- Platelet count > 600
- Both thrombosis and haemorrhage
- Burning sensation in the hands
- JAK2 mutation in 50%
Essential Thrombocytosis
Investigations
Raised platelet count (more than 600 x 10^9/l)
Essential Thrombocytosis
Management
- Aspirin to reduce risk of thrombus formation
- Chemo to control disease
- Hydroxyurea to reduce platelet count
- Interferon-alpha in younger patients
Thrombocytosis
Define
Thrombocytosis is an abnormally high platelet count, usually > 400 * 10^9/l
Thrombocytosis
Causes
- Reactive: platelets are an acute phase reactant - platelet count can increase in response to stress such as a severe infection, surgery. Iron deficiency anaemia can also cause a reactive thrombocytosis
- Malignancy
- Essential thrombocytosis, or as part of another myeloproliferative disorder such as chronic myeloid leukaemia or polycythaemia rubra vera
- Hyposplenism
Myelodysplastic syndrome
Pathophysiology
- Myeloid bone marrow cells do not mature properly
- Therefore do not produce healthy blood cells
- Pre-leukaemia –> may progress to AML
Myelodysplastic syndrome
Features
Bone marrow failure:
- Anaemia - pallor, fatigue, SOB
- Neutropenia (low neutrophils) - frequent/severe infections
- Thrombocytopenia (low platelets) - purpura or bleeding
Myelodysplastic syndrome
Investigations
- FBC: anaemia, neutropenia, thrombocytopenia
- Blood film: Blasts
- Bone marrow aspiration and biopsy
Myelodysplastic syndrome
Management
- Watchful waiting
- Supportive treatment with blood transfusions if severely anaemic
- Chemotherapy
- Stem cell transplantation
Myelodysplastic syndrome
Epidemiology
- More common with age (> 60 yrs)
- More common in those who have previously had chemo or radio therapy
Polycythaemia
Types
- Relative
- Primary (polycythaemia vera)
- Secondary
Causes of relative polycythaemia
- Dehydration
- Stress - Gasibock syndrome
Causes of primary polycythaemia
- Polycythaemia vera (proliferation of a marrow stem cell, erythroid cells)
Causes of secondary polycythaemia
- COPD
- Altitude
- Obstructive sleep apnoea
- Excessive erythropoietin:
- Cerebellar hemangioma
- Hypernephroma
- Hepatoma
- Uterine fibroids –> menorrhagia –> blood loss
How to differentiate between true (primary and secondary) and relative polycythaemia?
RED CELL MASS
In true polycythaemia the total red cell mass in males > 35 ml/kg and in women > 32 ml/kg
Thrombocytopenia
Pathophysiology
- Low platelet count
- Can either be due to low production or excess destruction
Thrombocytopenia
Problems with production
- Sepsis
- B12 or folic acid deficiency
- Liver failure –> reduced thrombopoietin production
- Leukaemia
- Myelodysplastic syndrome
Thrombocytopenia
Problems with destruction
- Alcohol
- ITP
- TTP
- Heparin-induced thrombocytopenia
- Haemolytic-uraemic syndrome
- DIC (using them up rather than destruction)
- Medications:
- Sodium valproate
- Clozapine
- Methotrexate
- Isotretinoin
- Antihistamines
- PPIs
Thrombocytopenia
Features
Platelets < 50 x 109/L
- Easy or spontaneous bruising and prolonged bleeding times
- Nosebleeds, bleeding gums, heavy periods, easy bruising or blood in the urine or stools
Platelet counts < 10 x 109/L
- High risk for spontaneous bleeding
- Spontaneous intracranial haemorrhage or GI bleeds are particularly concerning
Differentials of abnormal or prolonged bleeding
- Thrombocytopenia (low platelets)
- Haemophilia A and haemophilia B
- Von Willebrand Disease
- Disseminated intravascular coagulation (usually secondary to sepsis)
Causes of severe thrombocytopenia
- ITP
- DIC
- TTP
- Haematological malignancy
Causes of moderate thrombocytopenia
- HIT
- Drug-induced
- Alcohol
- Liver disease
- Hypersplenism
- Viral infection (EBV, HIV, hepatitis)
- Pregnancy
- SLE
- Antiphospholipid syndrome
- Vit B12 deficiency
Immune thrombocytopenia
Pathophysiology
- Antibodies are created against platelets
- Antibodies are directed against the glycoprotein IIb/IIIa or Ib-V-IX complex
Immune thrombocytopenia
Epidemiology
- More common in older females
Immune thrombocytopenia
Features
- May be detected incidentally
- Petichae, purpura
- Bleeding (e.g. epistaxis)
- Catastrophic bleeding (e.g. intracranial) = rare
Immune thrombocytopenia
Investigations
Platelets
Immune thrombocytopenia
Management
- Prednisolone = 1st line
- IV normal human immunoglobulin (IVIG): raises platelet count quicker than Pred so may be used if active bleeding or urgent invasive procedure is required
- Rituximab (monoclonal antibody against B cells)
- Splenectomy (now less common)
Immune thrombocytopenia
Other names for it
Autoimmune thrombocytopenic purpura
Idiopathic thrombocytopenic purpura
Primary thrombocytopenic purpura
Thrombotic Thrombocytopenic Purpura
Pathophysiology
- Abnormaly large or ‘sticky’ multimers of von Willebrand’s factor
- Causes platelets to clump in the vessels
- Deficiency of ADAMTS13 (normally present to break down multimers of von Willebrand’s factor)
- Platelets are used up here and therefore can not form clots –> bleeding
- The blood clots also break up RBCs leading to haemolytic anaemia
Thrombotic Thrombocytopenic Purpura
Features
- Fever
- Fluctuating neuro signs (microemboli)
- Microangiopathic hemolytic anaema
- Thrombocytopenia
- Renal failure
Thrombotic Thrombocytopenic Purpura
Causes
Deficiency in the ADAMTS13 can be autoimmune disease or inherited genetic mutation
- Post-infection, e.g. urinary, GI
- Pregnancy
- Tumours
- SLE
- HIV
- Drugs:
- Ciclosporin
- Oral contraceptive pill
- Penicillin
- Clopidogrel
- Aciclovir
Thrombotic Thrombocytopenic Purpura
Investigations
Platelets
Hb (low)
Renal function
Thrombotic Thrombocytopenic Purpura
Management
- Plasma exchange
- Steroids
- Rituximab (monoclonal antibody against B cells)