“I carry pain like you carry blood in your veins.” ~ Waseem Khan

In the past, structured laboratory tests that could detect genetic diseases were non-existent, and as a result, these diseases were not known. People lived average, unpredictable lives – they grew up, made friends, got married, gave birth, aged, did whatever else they wished, and hoped only for the best. The lack of scientific explanations for diseases, and for the painful deaths they often resulted in exonerated humans from the need to take responsibility. With the predominant traditional background that preceded civilisation in Africa, several misconceptions possibly existed for most of these diseases with unknown origins. For instance, it was common to hear of myths which attributed unusual mishaps to the gods: the order of revered beings, ancestors who could kill, or give life, and who had the power to make people suffer for their misdeeds.

Today, however, we know better. Scientific and technological advances have brought us solutions. Although there are still so many questions we do not yet have answers to, they are no longer shrouded in thick, uncertain, dark clouds like they were in the past

Sickle Cell Disease (SCD)

Introduction

Blood is a means of communication between cells of different parts of the body. The blood is made up of three types of cells: the red blood cells (RBC) or erythrocytes, the white blood cells (WBC) or leucocytes, and the platelets or thrombocytes.

Sickle Cell Disease (SCD) affects the red blood cells, the principal component of the blood. The disease is the most prevalent of the two known hemoglobin disorders, the other being Thalassemia.

The main function of red blood cells is to carry oxygen from the lungs to other organs and tissues, and carbon dioxide from these sites back to the lungs. Present in red blood cells is hemoglobin, a molecule that contains iron and aids in the transport of oxygen across the body. Anemia results when the body's hemoglobin or red blood cell level is below normal. SCD is the most common inherited anemia caused by abnormal hemoglobin. In SCD, the red blood cells lose their capacity to carry oxygen throughout the body adequately as a result of their abnormal hemoglobin.

Red blood cells have a concave shape that enables them to fold up as they move through narrow blood vessels. However, in the presence of the abnormal hemoglobin, RBCs lose this shape and become sickled (shaped like a new moon), sticky, and rigid when de-oxygenated. They form long polymers that get trapped easily in thin blood vessels, where they slow down or block blood flow and oxygen distribution. This series of events leads to tiredness, swelling of the area involved especially joints, and accounts for the severe pain SCD patients go through.

History

Prior to its rediscovery in the United States at the beginning of the 20th Century, SCD had been in existence in Africa for at least 5,000 years.

With its prevalence in malaria-endemic regions, it is widely believed that the disease is an environmental adaptation for survival. This is due to the fact that the error which leads to the disease confers malaria resistance in individuals who carry the trait for the disease. Nonetheless, sickle cell patients do not enjoy this immunity. They suffer severe malaria, as well as high malaria mortality rates.

Genetics

Like other genetic diseases, sickle cell disease is passed down from parents to their children. It results from a mutation to the gene that codes for the oxygen-carrying molecule in blood, hemoglobin (Hb). Mutations are modifications to the nucleotide sequence of our genes. These changes sometimes lead to abnormal conditions and diseases (SCD, Thalassemia, Huntington's disease, Down's syndrome, cancers, amongst others). Other times, they may be harmless or beneficial.

The single point mutation that gives rise to the disease involves the substitution of the hydrophobic amino acid, Valine for hydrophilic Glutamate in hemoglobin chains. Normal hemoglobin chains (HbA) have Glutamate, while mutated forms of the molecule (HbS) have Valine. The sticky patch that promotes the polymerisation of sickled red blood cells when they lose oxygen is created by this Glutamate to Valine substitution.

Individuals with SCD differ from those who carry the trait by the number of mutated genes they inherited from their parents. The symptomatic sickle cell patients inherited two dysfunctional Hb genes, one from each of their parents, and are said to be homozygous (SS). Carriers inherited only one copy of the sickle gene from either of their parents, are heterozygous (AS) for the disease, and thus, show no symptoms.

Statistics

Although there is limited information on the prevalence of SCD in Africa, available data show that the continent takes the lead on the global scene. Around 75% of all newborns living with SCD come from sub-Saharan Africa, a majority of whom live in Nigeria and the Democratic Republic of Congo (DRC). Over 300,000 babies are born every year with SCD, and this figure is expected to rise 33% to 400,000 by 2050. It is estimated that up to 2% of Nigeria's population live with SCD, whereas around 10 to 30% are reported to be carriers for the disease.

The lack of adequate infant screening tests and robust public health funding for SCD are major problems promoting the prevalence of the disease in Nigeria, and Africa at large.

Symptoms

The most common symptoms of sickle cell disease are anemia and episodes of severe pains, including acute chest syndrome (ACS). Others include fatigue, malaise, dizziness, and increased susceptibility to other diseases due to lowered immunity.