Let’s start at the beginning. What is Sickle Cell Disease?
You must have heard or read a lot of scientific talk and jargon, but let me break it down and explain everything for you; the what, how and why of this disease and why we should be talking about it.
Sickle cell disease (SCD) is an inherited blood disorder. While all races are affected by the disease, it is most prevalent among the black race and is the most prevalent genetic disorder in Africa. It is estimated that over 300.000 babies are born worldwide each year with SCD with over 75% of these births occurring in Sub-Saharan Africa.
SCD has an autosomal recessive pattern of inheritance from parents. This means that both parents will have to be carriers of the sickle cell trait in order to give birth to a child with SCD. Every child they give birth to has a 25% chance of having SCD, a 25% chance of not carrying the trait at all and a 50% chance of being a carrier.
People with the sickle cell trait usually do not have any of the symptoms of SCD and live a normal life. Thus only carrier testing can determine if a person is a carrier of the trait or not. A haemoglobin genotype test (a blood test) is usually done which is different from a blood group test.
Let’s say you take a haemoglobin genotype test: your result could be one of these three outcomes: AA, AS or SS.
If your result is AA, this means you are not a carrier of the sickle cell trait, nor do you have the disease. If it’s AS, this means you carry the trait and if it’s SS then you have the disease.
It’s therefore important to do a haemoglobin genotype test in order to be aware of your genotype.
SCD results in a structural abnormality in the oxygen-carrying protein called haemoglobin which is found in red blood cells. Under certain conditions, these red blood cells become rigid, shaped like sickles and are not able to pass through small blood vessels. This shape is where the disease gets its name.
Also, these abnormal red blood cells are destroyed quicker. The lifespan of the sickled cell is 10-20 days in contrast to 90-120 days for normal red blood cells. So people with SCD have chronic anaemia and their steady state haemoglobin level is 6-8g/d1.
They are able to participate in the activities of daily life in a normal fashion with this steady state haemoglobin but their tolerance for exercise and exertion tends to be very limited.
Interestingly, the sickle cell trait can reduce the risk of severe malaria by roughly 90%. As a result, sickle cell trait carriers are relatively protected from the danger of dying of malaria.
On the other hand, patients with SCD are highly susceptible to the lethal effects of malaria.
The simplest explanation is that malaria makes the anaemia of SCD severe. In addition, the often not functional spleen in people with SCD reduces the clearance of malaria parasites. As a chronic disease, the natural history of SCD is characterised by quiescent periods interspersed by acute events known as crises, leading to patients seeking health care and frequent hospitalisation. However, some patients remain virtually asymptomatic into or even through adult life.
Painful crises considered the hallmark of SCD, are defined as severe pain lasting for two or more hours that is attributable to SCD. Vasoocclusion, the underlying cause of the painful crises, occurs as a result of formation of aggregates that block blood flow in small blood vessels, depriving downstream tissues of nutrients and oxygen. The end result is tissue ischemia and tissue death resulting in excruciating pain.
Although no precipitating cause can often be identified, triggers such as respiratory infections, dehydration, fever, cold weather, alcohol intoxication, high altitude, pregnancy, emotional and physical stress have been identified. Avoiding these triggers therefore remains crucial to avoiding crises.
Ensuring high fluid intake daily, routine use of prophylactic penicillin and antimalarials, routine vaccination against certain germs and daily folic acid intake are all essential preventive measures.
I hope all of this now makes sense and if you have people around you who have the sickle cell disease, you are now aware what they have to live with.
To you taking care of family members and friends with the disease, continue to support them as much as you can. It makes all the difference.
And to the sickle cell warriors, you’re some of the strongest people at heart! Keep fighting and keep living!
Stay healthy until next time,
Dr. Ngwengi