Sickle Cell Anaemia Flashcards
What form of inheritance is sickle cell anaemia
Autosoma recessive
What causes sickle cell anaemia
Point mutation in codon 6 of the beta globin gene.
This alters the structure of the resulting Hb–> HbS
HbS polymerisis if exposed to low oxygen levels for a prolonged period–>results in distortion of the red cell and damaging the RBC membrane
what is a vaso-occlusive crisis
Blood vessels are obstructed due to sickled cells resulting n ischemia and severe pain
what is sickle cell trait (HbAS)
one abnormal gene (B/Bs)
it is an asymptomatic carrier state however they may sickle under sever hypoxia eg high altitude or under anaesthetic
What is the blood film appearance of sickle cell trait?
normal or mildly reduced MCV/MCH
Whhen does sickle cell anaemia occur
when the person has two abnormal genes (Bs/Bs)
HbS is more than 80 percent, no HbA, variable HbF
What are the complications of sickle cell anaemia
Vascular occlusion - digits, bone marrow, spleen, CNS, lung, renal, leg ulcers, very painful
Chronic haemolysis
Sequestration sickled RBCs in liver and spleen
WHat can precipitate a sickle crisis
hypoxia dehydration infection cold exposure stress/fatigue
What is the treatment of a painful sickle crisis
Opiates Hydration Rest Oxygen Antibiotics if due to infection red cell exchange transfusion in severe crises eg if chest or neuro symptoms
why does exchange help treat a crisis
it decreases the conc of HbS in blood–> improves tissue perfusion
what are the long term effects of sickle cell anaemia
poor growth
infections due to hyposplenism due to repeated infarcts
organ damage (Po Hypertension, renal disease, AVN, cva, impotence)
Psychosocial problems
What is the long term treatment of sickle cell anaemia
Avoid precipitants
Reduce infection risk - prophylactic penicillin, vaccinations
Folic acid supplementation
what does hydroxycarbamide do?
Can reduce severity of sickle cell anaemia by inducing HbF production
What other sickling disorders exist
HbS/B thalassaemia; mild if reduced B, severe if no B
HbSC disease; milder, increased risk of thrombosis
HbS/Dpunjab; severe
HbS/Oarab; severe
