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DTMH Block 4 > Tropical haematology > Flashcards

Tropical haematology Flashcards

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1
Q

What is haemolytic anaemia?

A

Anemia due to shortened RBC survival

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2
Q

How is haemolytic anemia classified?

A

Intra vs extravascular
Inherited vs acquired

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3
Q

What is the clinical presentation of haemolytic anemia?

A

Pallor
Jaundice
Gallstones
Splenomegaly

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4
Q

How can haemolysis be confirmed with laboratory markers?

A

Elevated
- indirect bili
- LDH
- reticulocyte count
Decreased
- haptoglobin
Urine haemosiderin *intravascular

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5
Q

What are the differences in the mechanism of intravascular vs extravascular haemolysis?

A

Intravascular = mechanical or complement mediated
Extravascular = immune mediated

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6
Q

What are the differences in the causes of intravascular vs extravascular haemolysis?

A

Intravascular = microangiopathies (DIC, TTP, HUS) vs macroangiopathies (mechanical heart valve)
Extravascular = autoimmune disorders

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7
Q

What are the differences in the hemolysis of intravascular vs extravascular haemolysis?

A

Intravascular = hemolysis in plasma
Extravascular = RBCs removed by RES

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8
Q

What are the differences in the haptoglobin level of intravascular vs extravascular haemolysis?

A

Intravascular = low haptoglobin
Extravascular = normal haptoglobin

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9
Q

What are the differences in the RBC shape of intravascular vs extravascular haemolysis?

A

Intravascular = non-spherocytic
Extravascular = spherocytes

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10
Q

What are the differences in the iron loss of intravascular vs extravascular haemolysis?

A

Intravascular = iron loss via haemosiderin excretion via kidneys
Extravascular = no iron loss

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11
Q

Name examples of genetic haematological disorders

A

Thalassemias
Sickle cell
G6PD
Haemoglobinopathies

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12
Q

Explain what haemoglobin is

A

Iron-containing oxygen transporting metalloprotein in RBC
Heme - iron at centre with hydrophobic pocket
Globin - 4 chains (2 alpha 2 non-alpha) stabilised by hydrogen bonds

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13
Q

How many alpha genes are on chromosome 16?

A

4 alpha genes (2 per chromosome)

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14
Q

How many beta globin genes are on chromosome 11?

A

5 functional genes
2 pseudogenes

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15
Q

What is the globin chain composition of haemoglobin A?

A

Alpha
Beta

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16
Q

What is the globin chain composition of haemoglobin A2?

A

Alpha
Delta

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17
Q

What is the globin chain composition of haemoglobin F?

A

Alpha
Gamma

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18
Q

What is the normal ratio of haemoglobin in an adult?

A

HbA >95%
HbA2 2-3%
HbF <1%

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19
Q

What is the difference in a thalassemia vs a haemoglobinopathy?

A

Thalassemia = decreased production of normal globin chain
Haemoglobinopathy = production of abnormal globin chain

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20
Q

Which thalassemia is rare in Africa?

A

Beta thalassemia (except Liberia and parts of North Africa)

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21
Q

Discuss the clinical features of a thalassemia

A

Hypochromic microcytic anemia
Tissue hypoxia
Skull deformities (frequent ear and sinus infections)
Pathological fractures
Stunted growth
HSM (causes secondary thrombocytopenia and leucopenia)

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22
Q

What is the difference in point mutations in beta thalassemia?

A

Beta - = absence of beta chain production from locus
Beta positive = partial deficiency of beta chain production from locus

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23
Q

What will the difference be in homozygous vs heterozygous beta thalassemia?

A

Homo - severe anemia
Hetero - mild anemia, elevated HbA2 on electrophoresis

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24
Q

Which ratio is highly suggestive of a thalassemia trait?

25
Discuss the genetics of alpha thalassemia
Normal genotype = aa/aa 1. 1 gene deletion (aa/-a) silent carrier 2. 2 gene deletion (a-/a- OR --/aa) mild anemia 3. 3 gene deletion (--/a-) Hb H disease 4. 4 gene deletion (--/--) Hb Barts hydrops fetalis = lethal
26
Why is 3 gene deletion called Hb H disease?
RBCs contain unstable beta 4 chains Beta 4 = Hb H
27
What is the difference in time of presentation for beta thalassemia vs alpha thalassemia?
Alpha - neonate Beta - 3 to 6m
28
Discuss the management of alpha thalassemia HbH disease
Folic acid supplement Avoid oxidant drugs Low iron diet +/- iron chelation therapy Splenectomy if severe Monitor closely in pregnancy
29
What is the mechanism of sickle cell disease?
Change of glutamine to valine (B chain, 6th aa) -> in deoxygenated form, Hb starts to polymerise and precipitate -> becomes rigid -> removed by spleen -> can clump in spleen, fingers, bone
30
How high is the heterozygote frequency of sickle cell in Africa?
40% (protective from falciparum malaria)
31
Which sickle cell patients are susceptible to falciparum malaria?
Homozygous
32
Discuss the clinical presentation of sickle cell disease
Children - pain, infection Adults - chronic organ damage 3 types of crisis - vaso-occlusive crisis - aplastic crisis - sequestration crisis Acute chest syndrome Recurrent strokes Leg ulcers Bone infarctions, OM Haematuria Priapism Cholestasis HSM Delayed puberty Retinal neovascularisation
33
What is vast-occlusive crisis?
Hypoxia Infection anywhere in body Painful
34
What is aplastic crisis?
Dramatic fall in Hb Parvovirus B19 Folate deficiency (pregnancy)
35
What is sequestration crisis?
Sudden, massive blood pooling in enlarged spleen -> hypotension Occurs in children
36
How is sickle cell disease diagnosed?
Hb 5-11 Normochromic normocytic anemia Sickle and target cell morphology Increased WCC Increased plt Electrophoresis (HbS present , HbF increased, HbA2 increased)
37
To which organisms are you predisposed to infection in sickle cell disease?
Encapsulated (s.pneumo, h.influenza, n. meningitidis) Salmonella (OM) If iron overloaded -> yersinia
38
Name precipitating factors for sickle cell disease symptoms
High altitudes Hypoxia (infarction) Low temperature (vasoconstriction) Low pH (acidosis) Infections (dehydration, acidosis, hypoxia)
39
What is sickle cell trait?
Less than half the Hb in each RBC is HbS - asymptomatic and only sickle if severe hypoxia or hyperosmolarity
40
Discuss management of sickle cell disease
Keep extremities warm Folate Hydroxyurea in patients with >3 crises per year Vaccinations Penicillin prophylaxis <6yo Stem cell transplant
41
Which biomarker must be monitored with hydroxyurea use?
White cell count
42
Discuss the management of acute vase-occlusive crisis
Hydration Analgesia (avoid pethidine) Oxygen Consider transfusion if severe sx anemia
43
Discuss the management of acute chest syndrome
Antibiotics Incentive spirometry Maintenance hydration only
44
Discuss the management of strokes
Exchange transfusion
45
What is HbC?
2 normal alpha chains and 2 variant beta chains Lysine replaces glutamic acid -> unstable Hb -> precipitates in RBCs and forms crystals -> decreased deformability and increased blood viscosity
46
What is HbE?
Point mutation in beta chain Change of glutamic acid to lysine Mild haemolytic with microcytosis and target cells
47
How is G6PD diagnosed?
Fluorescent spot test Spectrometry
48
Discuss classic TTP
Deficiency of von Willebrand factor cleaving protease -> circulating von Willebrand multimers and platelet microthrombi -> red cells fragment on micro thrombi -> microangiopathic hemolytic anemia
49
What is the pentad of TTP?
Fever Fragments Low plt Renal dysfunction Neurological symptoms
50
Discuss management of TTP
Exchange transfusion/plasmaphoresis Avoid giving plt Treat until LDH normalises
51
Which malignancies are associated with EBV?
Burkitt lymphoma Hodgkin lymphoma Primary CNS Primary effusion
52
Which diseases are associated with HTLV-1?
Adult T cell leukemia/lymphoma HTLV1 associated myelopathy Uveitis Myositis Dermatitis
53
What are the features of babesios?
Fever Mild HSM Haemolytic anemia
54
Discuss babesios
Disease of animals Confused with malaria (no pigment production or RBC changes) Thrombocytopenia Normal to low WCC
55
Discuss trypansosomiasis
African sleeping sickness Tsetse fly
56
Discuss the haematological abnormalities seen in trypanosomiasis
Dilutional anemia Leucocytosis Thrombocytopenia
57
Discuss leishmaniasis
Transmitted by phlebotamine sandfly
58
Discuss the haematological abnormalities seen in leishmaniasis
Normocytic normochromic anemia Pancytopenia (hypersplenism) Thrombocytopenia
59

DTMH Block 4 (14 decks)

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