Sickle cell disease

- Hemoglobinopathy caused by substitution of glutamic acid by valine at position 6 (from N terminal) of beta chain
- autosomal recessive
- 2 forms : heterozygous (HbAS) and homozygous (HbSS)
- low partial pressure of oxygen causes HbS to polymerise and precipitate, resulting sickling of erythrocytes.
- HbSS sickle at PO2 of 6kPa and HbAS/HbSC sickle at 4kPa
- Exchange transfusion is indicated when there is neurological damage or visceral sequestration crisis in sickle cell crisis
- most common cause of aplastic crisis is parvovirus infection
- salmonella osteomyelitis is seen in patient with sickle cell anemia
- Sickledex test involves the addition of reagent to blood, turbidity confirms the presence of HbS