Sickle cell is an inherited disease which affects the Haemoglobin in an autosomal recessive pattern. Males and females are affected equally and both parents must carry the abnormal genes, even if they have no symptoms for the child to be affected.
When both parents carry a single gene mutation HbAS(sickle cell trait) there is a 25% chance a child may get Sickle cell disease(HbSS), a 25% chance that a child will be unaffected(HbAA) and a 50% chance that they will inherit the genetic mutation(HbAS) as an asymptomatic carrier(this probability occurs in every single pregnancy).
The likelihood of parents getting children with Sickle cell disease is 25% if both parents are carriers of HbAS, 50% if one parent has HbAS and the other one is HbSS and 100% if both parents have HbSS i.e. Sickle cell disease.
Haemoglobin plays the role f transporting oxygen in the blood to the bodily tissues where it is required. Sickle haemoglobin has a curved sickle shape rather than the flat-disc-shaped cells of normal haemoglobin. The sickle shape causes red blood cells to become more rigid and less flexible making them hemolyze(shortened lifespan of 10-20 days instead of 90-120 days) and causing blockages in the blood vessels that disrupt the flow of blood.
BURDEN OF SICKLE CELL DISEASE
There is a paucity of data about the exact global burden of SCD, however, about 300,000 babies are born every year with sickle cell anaemia 90% of whom are found in Nigeria, the Democratic Republic of Congo, and India. These 3 countries have 2% of the population having SCD while the carrier prevalence rate is 10-30%.
It is projected that this number will surpass 400,000 by 2050 due to LMIC, MIC and now recording reduced infant mortality because of early diagnosis and treatment. It is estimated that 40% of people in some African countries have sickle cell trait, while in countries with poor resources, more than 90% of children with SCD do not survive to adulthood; about 1,000 children in Africa are born with SCD every day, and more than half will die before 5years of life.
Sickle cell distribution follows the malaria belt and HbAS is thought to protect people against severe malaria. People with HbAS are 90% less likely to develop severe malaria.
In Kenya, it is estimated that 4,000 children are born with SCD annually. A total of 21 out of 100 children in Kisumu are born with Sickle cell trait.