Sickling disorders

Question 1

what are sickling disorders?

Answer 1

Group of genetic disorders that affect the structure of haemoglobin, resulting in the production of HbS instead of HbA

Question 2

cause of sickling disorders?

Answer 2

Point mutation

-Point mutation in codon 6 of the beta globin gene that substitutes glutamine to valine producing beta s

Question 3

pathophysiology of sickling disorders?

Answer 3

-point mutation on codon 6 of the beta globin gene that substitutes glutamine to valine producing beta s

-HbS polymirises when exposed to low oxygen levels for prolonged period

-this distorts the red cell, damaging the RBC membrane

Question 4

how many normal beta genes does sickle cell trait (HbAS) have?

Answer 4

one normal, one abnormal beta genes

Question 5

how many normal beta genes does sickle cell (HbSS) have?

Answer 5

two abnormal beta genes

Question 6

presentation of sickle cell trait (HbAS)?

Answer 6

-asymptomatic carrier state
-very few clinical features as HbS is too low to polymerase
-may sickle in severe hypoxia (e.g. under anaesthesia or high altitude)

Question 7

investigations sickle cell trait (HbAS)?

Answer 7

blood film- normal
Mainly HbA (Hbs <50%)

Question 8

what is sickle cell anaemia?

Answer 8

a genetic condition that causes sickle (crescent) shaped red blood cells meaning they are easier to be destroyed leading to a haemolytic anaemia

Question 9

presentation of sickle cell anaemia?

Answer 9

Presentation depends on severity and site.

Vaso-occlusive crises - acute pain in the hands and feet due to vaso-occlusion of the small vessels

Hyposplenism due to repeated infarcts= increased risk of infection

Question 10

signs of sickle cell?

Answer 10

-Reticulocytes
-Anaemia
-Normal MCV
-Chronic haemolysis (RBC live 10-12 days usually live 120 days)
-Hyposplenism due to repeated infarcts= increased risk of infection
-Sequestration on RBC in liver/spleen
-HbS>80% and no HbA

Question 11

what causes hyposplenism in sickle cell anaemia?

Answer 11

the repeated infarcts

Question 12

what is the HbS and HbA in sickle cell anaemia?

Answer 12

HbS >80%
no HbA

Question 13

precipitants of sickle cell crisis?

Answer 13

-cold
-hypoxia
-dehydration
-stress
-fatigue
-infection

Question 14

symptoms of sickle cell crisis?

Answer 14

-Deep bone pain
-Digit pain
-Mesenteric ischaemia
-Avascular necrosis
-Priaprism

infants/children- swollen red fingers

Question 15

treatment of sickle cell crisis?

Answer 15

Opiates for pain
· Hydration, rest, oxygen

If chest/ neuro symptoms- consider exchange transfusion

Question 16

long term complications of sickle cell anaemia?

Answer 16

-impaired growth
-sepsis
-organ damage (pulmonary hypertension, renal disease, AVN, leg ulcers, stroke)

Question 17

how does sequestration of RBC in liver/ spleen present?

Answer 17

-spleen/ liver will be enlarged
-could have abdo pain from enlarged spleen/ liver
-may result in anaemia, marked pallor and cardiovascular collapse

Question 18

how does having sickle cell anaemia affect HbA1C and why?

Answer 18

-sickle cell anaemia gives a falsely low HbA1C due to the short RBC life span (10-12 days instead of 120 days)

Question 19

what cells are indicators of hyposplenism?

Answer 19

Howell Jolly bodies indicate hyposplenism

Question 20

A 9-month-old baby is brought to the emergency department with a swollen finger. He appears to be in a lot of pain and is crying and writhing around. His past medical history is significant for a diagnosis of sickle cell disease.

On examination, his left ring finger is hot, tender and swollen. His vital signs are stable.

What is needed to confirm the likely diagnosis in this patient?

Answer 20

In sickle-cell, acute painful vaso-occlusive crises should be diagnosed clinically

This boy has presented with a vaso-occlusive crisis of sickle cell disease. He is known to be affected and has a swollen digit (dactylitis), which is suggestive of vascular occlusion. Whilst other tests may be indicated to rule out infection or look at his haemoglobin levels, the diagnosis itself should be clinical only. Therefore the correct answer is that no extra tests are needed.

Question 21

what can occur if someone with sickle cell disease gets a parvovirus infection?

Answer 21

could have an Aplastic crisis

Question 22

signs of Aplastic crises?

Answer 22

-pancytopenia following a recent parvovirus infection
-bone marrow supression causes a reduced reticulocyte count

Question 23

what may be given if someone has repeated sickle cell crisis attacks?

Answer 23

hydroxyurea (as prophylaxis)

Question 24

what investigation can be done for definite diagnosis of sickle cell?

Answer 24

haemoglobin electrophoresis

Question 25

reticulocytes in aplastic crisis and when there is sequestration of RBC in liver/spleen?

Answer 25

aplastic crisis- reduced reticulocyte count

sequestration of RBC in liver/spleen- increased reticulocyte count

Question 26

what cells can be seen on blood film- sickle cell anaemia

Answer 26

target cells

Howell jolly bodies- due to hyposplenism

Question 27

what would be seen on chest Xray of someone having an acute sickle cell chest crisis?

Answer 27

bilateral patchy opacification