OVERVIEW

If you have sickle cell disease, it means you have a blood disorder that you acquired from either one or both parents.  As the name implies, the red blood cells in blood form a sickle shape.

This condition for years has been linked to life threatening complications such as anemia and multiple organ dysfunction, which may lead to death. With early diagnosis and suitable preventive measures, sickle cell disease can be managed, if not completely treated.

WHAT IS SICKLE CELL DISEASE (SCD)? 

Sickle Cell Disease is a broad term used for a group of inherited blood disorders. A person with a sickle cell disease has defective hemoglobin inherited from his/her parents. Hemoglobin (Hb) is a protein pigment inside red blood cells that carries oxygen from the lungs to the rest of the body and carbon dioxide from the body to our lungs to be expelled from our body system. 

A regular red blood cell (RBC) is flexible and is biconcave in shape. This allows it to easily move through blood vessels. For a person with SCD, the defective hemoglobin causes the red blood cells to be rigid and assume a sickle shape. As a result, many RBCs are destroyed as they squeeze through the blood vessels, causing a common disease, anemia. Also, there is the tendency of the destroyed RBCs to block tiny vessels; leading to severe health complications. Normal RBCs survive approximately 90-120 days. However, sickled red blood cells last for only 10-20 days.

WHO IS AT RISK?

 

It is estimated that one in every 250,000 babies is born annually with SCD. However, SCD is more common amongst the African population (Sub Saharan Africa) and African-Americans. Others who are at risk include: Hispanics, Southern Europeans and Middle Eastern or Asian Indian backgrounds.

 

About 1 out of every 365 black children is born with SCD. According to Egbochuku, E. O, Imogie, A. O; Nigeria, by virtue of her large population, has the greatest number of people suffering from SCD.

Tanzania records one of the highest annual births of Sickle Cell Diseased individuals in the world. It’s estimated to reach 11000 births each year. Without appropriate intervention, 50–90% of children will not live pass 10 years.

 

Over the years, Ghana has seen a remarkable progress in the control of diseases such as tetanus, poliomyelitis, measles but inherited blood disorders such as sickle cell disease and thalassemia are still on the rise. 30% of the Ghanaian population are carriers of sickle cell disease. According to Dr. Ama Kyerewaa Edwin of the Korle Bu Teaching Hospital, 1 out of 3 Ghanaians has the hemoglobin S and/or C gene. 2% of newborns in Ghana are estimated to have the sickle cell disease.

DEFECTIVE HEMOGLOBIN

A defective hemoglobin that is inherited has the tendency to cause a blood disorder.

7% of the world’s population carry a defective hemoglobin gene. According to the World Health Organization, 300,000-500,000 babies with a defective hemoglobin are born each year.

 A normal hemoglobin exists in 3 forms, hemoglobin A (major after 12 weeks old), hemoglobin A2 (major before 12 weeks old), hemoglobin F (major in fetuses). Each hemoglobin consists of 3 pairs of different globin chains; two alpha chains coupled with either two beta chains (HbA), two delta chains (HbA2) or two gamma chains (HbF).

 In SCD, genes necessary for a normal globulin beta chain (HbA) is replaced with a sickle cell gene (HbS) or an abnormal hemoglobin gene (HbC or HbE). This abnormal exchange of genes, tends to affect the structure of the hemoglobin leading to SCD. Usually, it is assigned letters (S, D, E, O) which stands for where the disease was first discovered. Furthermore, SCD interferes with the functional abilities of the hemoglobin leading to a clinical disorder.

TYPES OF SICKLE CELL DISEASE

The types of SCD depend on the kind of genes that a person inherits. Defective genes exit in 2 different forms;

  • Beta hemoglobin variants (HbS, HbC, HbE)
  • Beta Thalassemia (Absent or Deficient Beta globulin synthesis)

People with sickle cell disease usually inherit:

  1. A sickle cell gene, (S), inherited from each parent, results in a type of SCD known as Hemoglobin SS sickle cell disease. This is the most severe and most common type of SCD. But, when one out of the two genes received from each parent is normal, its results in an SCD known as Hemoglobin AS or a sickle cell trait.
  • Hemoglobin SS (HbSS)
  • Hemoglobin AS (HbAS)
  1. A sickle cell gene, (S), from one parent and an abnormal hemoglobin gene (C, D, E, O) from the other parent. This results in the following types of SCD:
  • Hemoglobin SC (HbSC)
  • Hemoglobin SD (HbSD)
  • Hemoglobin SE (HbSE)
  • Hemoglobin SO (HbSO)
  1. A sickle cell gene, (S) from one parent and one Beta thalassemia gene [(“o”-absent gene), (“+”-diminished gene)], from the other parent, leads to the following types of SCD.
  • Hemoglobin S beta O thalassemia (HbS B’O’ thalassemia)
  • Hemoglobin S beta + thalassemia (HbS B’+’ thalassemia)

A person may also inherit a sickle cell gene from one parent and a normal gene from the other. Such a person is known to have a sickle cell trait.  This person may not show symptoms but is capable of transferring the trait and disease to future children.   

CAUSES OF SICKLE CELL EPISODES

SCD is caused by a defect in hemoglobin that works to carry oxygen into and out of tissues. Therefore, factors that seem to stress Hemoglobin activity results in Sickle Cell episodes. Some of these include:

  • Low oxygen pressure in the blood e.g. at high altitudes
  • Strenuous activities e.g. running
  • Decrease in blood plasma volume e.g. hemorrhage
  • Decrease in blood PH e.g. Kidney problems

SYMPTOMS OF SICKLE CELL DISEASE

The symptoms of SCD vary widely from person to person. This results from underlying complications of the disease itself. Symptoms usually show around 5 months of age . Some symptoms include:

  •  Signs of infection (fever, breathing difficulties, changes in appetite)
  • Signs of anemia (fatigue, pale skin, yellowish skin and eyes)
  • Vomiting and diarrhea
  • Severe pain crisis when blood vessels are blocked by sickle shaped hemoglobin in hands, feet, back and joints.
  • Swollen abdomen and feet

DIAGNOSIS OF SICKLE CELL DISEASE

  • Blood test: to check the level of hemoglobin, as well as abnormal structure of the RBCs.
  • Screening test such as prenatal screening and new born screening to check for abnormal hemoglobin traits.
  • DNA test: to confirm the diagnosis and the exact sickle cell type.

COMPLICATIONS

Individuals with SCD experience a lifetime of illness, as well as decreased life span.  SCD is a disorder that later leads to a number of severe complications; some of these include:

  • Kidney disease
  • Acute chest syndrome- the leading cause of death in SCD
  • Liver complications
  • Increased risk of infection due to non-functional spleen
  • Retarded growth
  • Eye problems
  • Jaundice and gallstones
  • Painful erection
  • Pulmonary hypertension
  • Stroke
  • Joint problems

 TREATMENT

An acquired defective gene cannot be cured. However, certain measures can be used to prevent some of the symptoms and complications of SCD.

  • Bone marrow transplantation
  • Blood transfusion
  • Pain management
  • Psychotherapy
  • Surgery
  • Hydroxyurea – a drug that increase the production of fetal hemoglobin.
  • Antibiotics
  • Childhood immunization

Research indicates that, one-third of children with SCD, present with neuropsychological complications. In addition, these complications manifest as deficits in their thinking abilities as well as academic difficulties. Many parents are ignorant about the disease. As a result, there is often poor management, leading to a low-quality of life. Couples who carry the SCD traits must understand the future impact of the disease before deciding on having children.

Finally, premarital genotypic counselling is recommended in order to reduce the chances of having a child with SCD. There is a 25% chance the baby will inherit two sickle cells genes and have sickle cell anemia, when both parents have a sickle cell trait that’s not evident.