Sickle-cell anaemia (also known as sickle-cell disorder or disease) is a common genetic condition due to a haemoglobin disorder, which is inherited from generally healthy parents with mutant haemoglobin genes (WHO 2006).
Sickle cell anaemia is prevalent in Africa, the Middle East, and parts of India and is common in geographical areas where malaria is widespread (Moavia et al, 2018). In sub Saharan Africa, it constitutes a real public health issue with 1–4% of babies born affected (Rees et al 2010).
In Cameroon, around 20% of the population carries the sickle cell trait (Ama et al 2012), and the disease prevalence is estimated at 0.6% in the general population (Yanda et al 2017).
In most parts of Africa, the disease is exacerbated by inadequate health infrastructure, poor nutrition and infectious conditions like malaria, tuberculosis and HIV (Mburu et al 2019).
SCD encompasses a group of disorders characterized by the presence of at least one hemoglobin ‘S’ allele and a second pathogenic variant resulting in abnormal hemoglobin polymerization (Bender, 2017). Sickle cell anemia is a severe form of SCD and is the homozygous state for HbS.
In a study in Yaounde involving 703 babies, 0.75% were Hb S/S (homozygous) and 16.8% heterozygous Hb A/S (heterozygous).
Human erythrocytes sickle because their abnormal sickle hemoglobin (HbS) polymerizes following deoxygenation in vivo and in vitro (Steinberg 2019). Hypoxia‐induced polymerization of the abnormal HbS is the single indispensable event that drives the pathophysiology of sickle cell disease. The intracellular polymerization leads to distorted cell morphology (sickling), hemolysis, altered blood viscosity, circulatory sludging with occlusion of blood flow from adherent sickle erythrocytes and white cells at the level of capillaries and postcapillary venules.
In addition, endothelial activation and injury results from chronic anemia and systemic inflammatory state with characteristic features of elevated leukocyte counts, activation of granulocytes and monocytes, elevation of inflammatory mediators, acute‐phase reactants, and soluble adhesion molecules, activation of hemostatic systems, and excess oxidant generation. This ultimately causes tissue and end‐organ damage resulting in symptoms of the disease (Mburu et al 2019) .
Clinical consequences of SCD include:
Hemolysis
Anaemia
Choleliathiasis
Aplastic anaemia
Vasooclusion
Pain
Acute splenic sequestration
Leg ulcers
Priapism
Organ dysfunction
Neurologic events
Stroke
Cognitive/silent
Retinopathy
Chest
Acute chest syndrome
Pulmonary hypertension
Avascular necrosis of the femoral head
Renal disease
Infections
Malaria
Bacterial infection.
(Makani et al 2013)