I have seen more children with sickle cell disease during this stay in Zambia than my other two tours. It is a miserable, dreadful disease.
It is a genetic disorder of haemoglobin which alters the biconcave disc shape of red blood cells into a crescent or sickle. Being an autosomal recessive condition, a sufferer needs to inherit a sickle gene from both parents to be severely affected (HbSS). Only having one gene (sickle cell trait, or HbS) causes no problems (unless the oxygen level of the blood is reduced) and confers some protection against malaria. (This may be why evolutionary pressure has not eliminated the disease.) Paradoxically, patients with sickle cell disease (HbSS) are more susceptible to the dangerous form of falciparum malaria which can be fatal.
Fetal haemoglobin (HbF) helps to protect babies for the first six months of life, but as HbF disappears, the affected child starts to become symptomatic. The abnormally-shaped red cells clog up the micro blood supply to bone marrow, causing acute and long-standing pain in the bones. The deformed red cells cannot revert to normal and they burst or haemolyse. The child becomes anaemic with less than 50% of the amount of haemoglobin as a child without sickle cell disease.
The sickling blood cells are filtered out by the spleen, which grows in size and then becomes destroyed as its capillaries clog up. The spleen is the location of immunological memory cells, which are lost when the spleen infarcts. This makes the child more susceptible to bacterial infections, especially streptococcal, meningococcal and salmonella (typhoid) infections.
Sickling cells also damage the lungs, causing chest pains and difficulty breathing. A stroke can result from sludging of red blood cells in the brain.
The child’s growth falters and the child is often stunted. Leg ulcers are a common complication which are very slow to heal.
Sickling crises can occur spontaneously but may be precipitated by lack of oxygen, dehydration or altered body temperature.
At the health centre, on Fridays, the laboratory runs a batch of tests for sickle cell disease. A drop of blood is mixed with a reducing agent to take away oxygen, which causes the cells to change into their classic sickle shape, seen under the microscope. Unfortunately, we have run out of reagent to do this test, so we have to send suspected children to the nearest district hospital, an hour away by bush taxi.
There is no cure for sickle cell disease apart from a stem cell transplant – but this is not an option in Zambia. We can correct the anaemia by blood transfusion, but this may only last a few weeks. We avoid giving iron tablets because of the risk of iron overload from frequent transfusions. Sadly we don’t have any stocks of folic acid, which helps red cell production. At the time of writing, we don’t even have paracetamol to treat painful crises. We do have polyvalent pneumococcal vaccine.
This is another condition where we can make the diagnosis but offer only limited symptomatic treatment with no hope of a cure. Most of our patients will not reach adulthood. It makes me feel depressed and impotent.