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Haematology- Carol > 1.06 Haemoglobinopathies > Flashcards

1.06 Haemoglobinopathies Flashcards

1
Q

HbA

A

2 alpha

2 beta

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2
Q

HbA2

A

2 alpha

2 delta

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3
Q

HbF

A

2 alpha

2 gamma

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4
Q

What is the distribution of Hb in adults?

A

HbA- 97%
HbA2- 2.5%
HbF 0.5%

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5
Q

alpha genes

  • number
  • chromsome
A

4 per cell - 2 per chromosome

on chromosome 16

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6
Q

beta genes

  • number
  • chromosome
A

2 per cell - 1 per chromosome

on chromosome 11

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7
Q

thalassaemias

A

decreased rate of globin chain production

unbalanced accumulation of globin chains –> ineffective erythropoiesis and haemolysis

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8
Q

structural hb variants

A

normal production of structurally abnormal globin chains

-HbS

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9
Q

alpha thalassaemia

A

alpha chains affected

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10
Q

beta thalassaemia

A

beta chains affected

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11
Q

reduced synthesis of alpha globin

A

a^+

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12
Q

absent synthesis of alpha globin

A

a^o

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13
Q

which mutation is most common in the cause of alpha thalassaemia?

A

deletional mutation

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14
Q

point mutation alpha thalassaemia

A

rare
more profound alpha chain reduction
non-deletional a-thalassaemia

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15
Q

which hb are affected in alpha thalassaemia?

A

HbA
HbA2
HbF

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16
Q

what are the 4 classifications of alpha thalassaemias?

A
  • a/aa= silent a-thal trait
  • a/-a or –/aa = a-thal trait
  • -/-a = HbH disease
  • -/– = Barts hydrops fetalis = no functional a-genes
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17
Q

alpha thal trait
–/aa

clinical and lab findings?

A

clinically asymptomatic
microcytic hypochromic red cells, mild anaemia
normal ferritin
raised red cell count
HbH bodis - red ell inclusions can be seen sometimes = golf ball appearance

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18
Q

HbH disease

lab findings?

A

severe

a-chain production is

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19
Q

HbH clinical findings?

A

asymptomatic to transfusion dependent
splenomegaly- extramedullary haematopoiesis
jaundice- haemolysis, ineffective erythropoiesis
growth retardation
gallstones
iron overload

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20
Q

Inheritance of HbH?

A

autosomal recessive

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21
Q

Mx of HbH?

A

mild- tranfusion at intercurrent illness
severe- transfusion dependent
splenectomy- vaccinate and prophylaxis for encapsulated bacteria
folic acid supplements

22
Q

HbBarts

A

4 gamma globulins

23
Q

clinical features of barts hydrops fetalis syndrome

A 
pallor 
oedema
cardiac failure
growth retardation 
severe hepatosplenomegaly
skeletal and cardiovascular abnormalities

most die in utero, some de shortly after birth

24
Q

preventing barts hydrops fetalis

A

antenatal screening high risk parents

  • family origin questionnaire
  • fbc
  • further testing if either flagged up

counsel couples at risk
prenatal diagnosis with selective termination

25
Q

dx of alpha thalassaemia

A

red cell indices + ethnicity
rule out iron deficiency
blood film- target cells, anisopoikilocytosis

liquid chromatography or electrophoresis to quantify Hb, identify abnormal Hb, and exclude beta-thal trait

26
Q

what alpha-thal mutation is found in all populations?

A

-a^3.7 (a+ mutation)

27
Q

what alpha thal mutation is more common in SE asia?

A

–^SEA (a0 mutation)

28
Q

Which Hb type is affected in beta-thalassaemia?

A

HbA

29
Q

what is the usual mutation and inheritance pattern of beta thal?

A 
point mutation (opposite of alpha thal) 
autosomal recessive inheritance (like alpha thal)
30
Q

beta thal trait

-general description

A

B+/B or Bo/B
asymptomatic
low MCV/MCH
raised HbA2 is diagnostic (2 alpha 2 delta)

31
Q

beta thal intermedia

-general description

A

B+/B+ or Bo/B+
moderate severity
occasional transfusion

32
Q

beta thal major

-general description

A

severe, lifelong transfusion dependency

33
Q

Anaemia found in beta-thal major?

A

mod-severe anaemia 30-90g/L
very low MCV/MCH
reticulocytosis
film: anisopoikilocytosis, target cells

HPLC(liquid chroma)

  • HbF mainly
  • small amounts HbA
  • HbA2 often elevated
34
Q

clinical features of beta-thal major

A 
presenting 6-24 months with 
failure to thrive
pallow
extrapedullar paematopoiesis- hepatospenomegaly
skeletal change
organ damage
35
Q

management of b-thal major

A

regular transfusion to maintain 95-105g/L

  • suppress erythropoiesis, inhibit overabsorption of iron
  • avoid iron overload (desferro)
  • consider bone marrow transplant before complications
36
Q

Transfusion related complications

A

viral- HIV, HepB, HepC
alloantibodies = hard to cross match
transfusion reactions

Other:
bacterial sepsis

37
Q

consequences of iron overload

A

endo: impaired growth and pubertal development, DM, osteoporosis
cardiac: myopathy, arrhythmias

liver: cirrhosis, hepatocellular cancer

38
Q

how much iron per unit of RBC?

A

250mg

39
Q

iron chelating drug

A

desferrioxamine

binds iron and complexes excreted in urine or stool

40
Q

sickle cell anaemia inheritance and mutation pattern?

A

autosomal recessive

point mutation in codon 6 of beta-globin gene (glutamine to valine)

41
Q

what is the problem with HbS?

A

polymerises at low oxygen levels
distortion of red cell
damages RBC membrane

42
Q

HbAS

What is this disease?
What is the impact?

A

sickle cell trait
only 1 abnormal beta gene
asymptomatic carrier state
may sickle in severe hypoxia- high altitude, or under anaesthesia

43
Q

What are the lab findings of HbAS?

A

blood film- normal or mild decrease in MCV?MCH

mainly HbA, HbS

44
Q

HbSS
what is this disease?
what is the impact?

A

this is sickle cell anaemia- no abnormal b-genes
HbS >80%, no HbA, variable HbF

tisue infarction- digits, bone marrow, spleen, CNS, lung, renal, leg ulcers, pain +++
chronic haemolysis
sequestration of sickle cells in liver and spleen

45
Q

What are the 5 ppts of sickle crisis?

A 
hypoxia
dehydration 
infection 
cold exposure
stress/fatigue
46
Q

How do you treat a painful crisis of sickle cell anaemia?

A

opiates
hydration
rest oxygen
antibiotics if s/s infection

red cell exchange transufusion in extreme crisis- chest crisis or neurological symptoms

47
Q

LT effects of sickle cell anaemia?

A

poor growth
infections- hypospleenism due to infarcts
organ damage- pulmonary hypertension, renal disease, avascular necrosis of bines, CVA, impotence
psychosocial problems

48
Q

long term treatment of sick cell anaemia

A 
education/lifestyle avoid PPTs
reduce infection risk 
-penicillin prophylaxis 
-vaccination- pneumococcus, meningococcus, haemophilus 
-folic acid supplmentation

-hydroxycarbamide, hydroxyurea can reduce severity of this disease by inducing HbF production

49
Q

mild or severe:

HbS/B thalassaemia

A

mild if B+ (reduced)

severe if Bo (absent)

50
Q

mild or severe:

HbSC

A

milder but increased risk of thrombosis

51
Q

mild or severe:

HbS/Dpunjab

A

severe

52
Q

mild or severe:

HbS/Oarab

A

severe

Haematology- Carol (29 decks)

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