Sickling disorders Flashcards
what are sickling disorders?
Group of genetic disorders that affect the structure of haemoglobin, resulting in the production of HbS instead of HbA
cause of sickling disorders?
Point mutation
-Point mutation in codon 6 of the beta globin gene that substitutes glutamine to valine producing beta s
pathophysiology of sickling disorders?
-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
how many normal beta genes does sickle cell trait (HbAS) have?
one normal, one abnormal beta genes
how many normal beta genes does sickle cell (HbSS) have?
two abnormal beta genes
presentation of sickle cell trait (HbAS)?
-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)
investigations sickle cell trait (HbAS)?
blood film- normal
Mainly HbA (Hbs <50%)
what is sickle cell anaemia?
a genetic condition that causes sickle (crescent) shaped red blood cells meaning they are easier to be destroyed leading to a haemolytic anaemia
presentation of sickle cell anaemia?
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
signs of sickle cell?
-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
what causes hyposplenism in sickle cell anaemia?
the repeated infarcts
what is the HbS and HbA in sickle cell anaemia?
HbS >80%
no HbA
precipitants of sickle cell crisis?
-cold
-hypoxia
-dehydration
-stress
-fatigue
-infection
symptoms of sickle cell crisis?
-Deep bone pain
-Digit pain
-Mesenteric ischaemia
-Avascular necrosis
-Priaprism
infants/children- swollen red fingers
treatment of sickle cell crisis?
Opiates for pain
· Hydration, rest, oxygen
If chest/ neuro symptoms- consider exchange transfusion
long term complications of sickle cell anaemia?
-impaired growth
-sepsis
-organ damage (pulmonary hypertension, renal disease, AVN, leg ulcers, stroke)
how does sequestration of RBC in liver/ spleen present?
-spleen/ liver will be enlarged
-could have abdo pain from enlarged spleen/ liver
-may result in anaemia, marked pallor and cardiovascular collapse
how does having sickle cell anaemia affect HbA1C and why?
-sickle cell anaemia gives a falsely low HbA1C due to the short RBC life span (10-12 days instead of 120 days)
what cells are indicators of hyposplenism?
Howell Jolly bodies indicate hyposplenism
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?
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.
what can occur if someone with sickle cell disease gets a parvovirus infection?
could have an Aplastic crisis
signs of Aplastic crises?
-pancytopenia following a recent parvovirus infection
-bone marrow supression causes a reduced reticulocyte count
what may be given if someone has repeated sickle cell crisis attacks?
hydroxyurea (as prophylaxis)
what investigation can be done for definite diagnosis of sickle cell?
haemoglobin electrophoresis
