Sickle cell disease

Question 1

What

Answer 1

AR - homozygous = sickle cell anaemia; heterozygous = SC trait
Production of abnormal beta globin chains
Strange haemoglobin which polymerises when deoxygenated -> deformed sickle RBCs
These are fragile and haemolyse and also block small vessels
Common in those of African descent

Question 2

Presentation

Answer 2

Chronic haemolysis generally well-tolerated (except in crises)
Crises:
1) Vaso-occlusive 'painful' crisis
2) Aplastic crisis
3) Sequestration crisis

Question 3

Vaso-occlusive ‘painful’ crisis

Answer 3

Common
Due to microvascular occlusion
Often affects the marrow -> severe pain
>3 years old: hands and feet -> dactylitis
Mesenteric ischaemia -> acute abdomen
CNS infarction (10% children) -> stroke, seizure, cog deficits
Avascular necrosis eg of femoral head
Leg ulcers
Priapism
Triggered by cold, dehydration, infection, hypoxia

Question 4

Aplastic crisis

Answer 4

Sudden reduction in marrow production, esp RBCs
Due to parvovirus B19
Usually self-limiting <2wks, may need transfusion

Question 5

Sequestration crisis

Answer 5

Mainly affects children as spleen not yet undergone atrophy

Pooling of blood in spleen +/- liver -> organomegaly, severe anaemia and shock. Urgent transfusion needed

Question 6

Complications

Answer 6

Splenic infact occurs before 2 years old (microvascular occlusion) -> increased infection - 40% of childhood sickle cell deaths. Zinc supplements may help
Poor growth
Chronic renal failure
Gallstones
Retinal disease
Iron overload or blood born virus after repeated transfusion
Lung damage (hypoxia -> fibrosis -> pulm HTN)

Question 7

Management of chronic disease

Answer 7

Refer to haematology
Hydroxycarbamide if frequent crises
Prophylactic abx and immunisations as is hyposplenic
Increased risk of sepiticaemia. Can attempt to avoid repeated admission with outpatient IV ceftriaxone, but admission may still be needed. Seek expert advice
Bone marrow transplant can be curative but is controversial

Question 8

Prevention

Answer 8

Genetic counselling
Prenatal tests
Parental education can help prevent 90% of deaths from sequestration crises

Question 9

Managing crises

Answer 9

Prompt, generous analgesia (eg IV opiates)
Bloods: crossmatch, FBC, reticulocytes, cultures
Other inv: MSU +/- CXR if febrile or chest signs
Rehydrate with IVI, keep warm, O2 if sats <95%
Blind abx (cephalosporin) if T >28, unwell or chest signs
Measure packed cell volume, reticulocytes, liver and spleen size 2x/day
Blood transfusion if Hb or retics fall sharply. Match blood well to prevent Ab formation