Did you know that:

• 25 % of Nigerians are carriers for sickle cell, that is, one in four Nigerians carry the sickle cell gene.
• Nigeria has the largest number of people suffering from sickle cell disease in the world.
• Every year, around 150,000 (one hundred and fifty thousand) Nigerian babies are born with sickle cell disease.
• About sixty percent of these children die before they reach 5 years of age.

So What is sickle cell disease (SCD)?

Sickle cell disease is an inherited blood disorder that affects red blood cells. People with sickle cell disease have red blood cells that contain mostly ‘hemoglobin S’ or ‘sickle hemoglobin’ (HbS), an abnormal type of hemoglobin. Sickle hemoglobin causes the red blood cells to develop a sickle shape.

Sickle cells are stiff and sticky. They tend to block blood flow in the blood vessels of the limbs (arms and legs) and organs. This blocked blood flow around the body is what causes the characteristic pain associated with the disease (most commonly pain in the arms, legs, chest, back, and abdomen). Blocked blood flow may also result in multiple organ damage and an increased risk for infections (like pneumonia)

So what is Hemoglobin?

Hemoglobin is a protein in our blood that transports oxygen around our body. For short, it is the oxygen-carrying molecule in our blood. Hemoglobin is the main substance of the red blood cell. Hemoglobin transports the oxygen we breathe in from our lungs to the rest of our body. Normal blood cells contain Hemoglobin A (HbA). Sickled blood cells contain Hemoglobin S (HbS). Hemoglobin S causes red blood cells to form a sickle shape.

• Normal red blood cells are round and flexible, which enables them to travel easily through the body’s small blood vessels.
• Normal red blood cells have a lifespan of 120 days.
• Sickle-shaped cells have a lifespan of only 10 to 20 days.
• Sickle-shaped cells are stiff and sticky, they break apart easily thereby causing anemia.
• Anemia is a deficiency of red blood cells or of hemoglobin in the blood often resulting in pale skin, weakness, and shortness of breath.
• Sickled red blood cells clump together and stick to the walls of the blood vessels, thereby blocking blood flow.
• This causes severe pain and permanent damage to bodily tissues and vital organs such as the heart, brain, lungs, kidneys, liver, bones, and spleen.

The resulting severe pain in a sickle cell warrior is an emergency called “acute sickle cell crisis”.
flow

Photo credit: National Heart, Lung, and Blood Institute (A division of the NIH)

Who can get sickle cell disease?

Sickle cell disease is genetic; and therefore any human baby with two parents who carry at least one HbS gene can inherit the disease. However, sickle cell disease is most common amongst those with ancestral roots in Africa, South or Central America, Caribbean islands, India, the Middle East, Saudi Arabia and Mediterranean countries (such as Turkey, Greece and Italy).

How is sickle cell disease inherited?

Sickle cell is a genetic disease; meaning it can only be inherited, it is not contagious.

A person will be born with sickle cell disease only if two HbS genes are inherited- that is, one sickle cell gene from the mother and one from the father.

A person who inherits only one HbS gene is healthy and is said to be a “carrier” of the disease OR as having “sickle cell trait”.

A carrier does not have sickle cell disease and will not under normal circumstances, exhibit any symptoms of the disease.

However, a carrier has a high chance of having a child with sickle cell disease if he or she has a child with someone who also carries a sickle cell gene.

Below are “punnett squares” representing the heritability of sickle cell disease under varying circumstances:

CASE 1: Each carrier parent, AS (mother or father) and AS (mother or father) could give either an A or an S to the next generation. There is an equal chance for giving either to the next generation.

 

Each child’s chances are:25% chance of being a non-carrier (AA)

25 % chance of having the disease (SS)

50% chance of being a carrier (AS)

CASE 2: In the case below, only one parent carries the HbS gene. And so, although it is possible for the children to be carriers for the disease, it is not possible for any of their children to have sickle cell. Again there is an equal chance that the carrier parent will give either A or S to the next generation.

 

Each child’s chances are:

50% chance of being a carrier (AS)

50% chance of being a non-carrier (AA)

0% chance of having the disease (since only one parent carries S)

CASE 3: In the case below, one parent is a carrier (AS) while the other parent has sickle cell disease (SS). In this case, it is impossible for any of the children to be non-carriers (AA). In this case, there lies a greater chance of having a child with sickle cell disease. Remember, there is an equal chance that the carrier parent will give either A or S to the next generation.

 

Each child’s chances are:

50% chance of being a carrier (AS)

50% chance of having sickle cell (SS)

0% chance of being a non-carrier (AA)

CASE 4: In the case below, both parents have sickle cell disease (SS) and (SS). Therefore ALL the children they have will have sickle cell disease.

Each child’s chances are:

100% chance of having sickle cell disease (SS)

This is the only possibility.

The case below is the only condition under which there lies NO POSSIBILITY of a child being a carrier of sickle cell or of having sickle cell disease.

Each child’s chances are:

100% chance of being a non-carrier (AA)

This is the only possibility since neither parent carries the HbS gene.

Note that the inheritability of sickle cell disease is random.

If you have sickle cell disease or if you are a carrier, procreating with a non-carrier (AA) is the most efficient way of ensuring that none of your children has the disease.

Symptoms of Sickle Cell Disease

Anemia: a deficiency of red blood cells or of hemoglobin in the blood.

Pain crisis: also referred to as ‘acute sickle cell crisis’ or ‘sickle crisis’. This can be triggered by many conditions including infection, stress, and dehydration. The warrior suffers excruciating and severe pain in the body. Pain crises can last anywhere from a few minutes to a few weeks.

Jaundice: yellowing of the skin, eyes, and mouth. Because sickled cells have a shorter life span than normal cells, therefore they die at a faster pace than the liver is able to break them down and filter them out of the body. Bilirubin is the yellow breakdown product and its excessive presence is what results in jaundice/yellowing.

Acute chest syndrome: this is when sickled cells stick together and block the flow of oxygen in the tiny blood vessels in the lungs. This includes pain, fever and a violent cough. Damage to blood vessels in the lungs can lead to high blood pressure in the lungs (pulmonary hypertension).

Splenic sequestration: this happens when a lot of sickled cells are trapped in the spleen. This causes sudden weakness, pale lips, rapid breathing, excessive thirst, belly pain, and a rapid heartbeat. Sequestration is mostly common in children under 5 and is considered to be the second leading cause of death in sickle cell warriors aged 10 and under. The spleen is an organ that purifies the blood and helps the body to fight infections.

Splenomegaly: this is an enlargement of the spleen caused by repeated sequestration. Splenomegaly is what makes sickle cell warriors appear to have big stomachs. A person is more likely to have serious life-threatening infections when their spleen is not functioning normally.

Priapism: a persistent and painful erection that could last more than four hours and occurs without sexual stimulation or arousal. Priapism occurs when the blood vessels in the penis are obstructed by sickled cells. If not promptly treated, it can result in impotence.

Stroke: this happens when sickled cells block the major blood vessels that supply the brain with oxygen.

Gallstones: these are hardened deposits that form in the gallbladder as a result of excess bilirubin in the sickle cell warrior. (The gallbladder is a small organ located under the liver. It aids in the digestion of fatty foods).

Increased infections: this is the leading cause of death in children with SCD.

Delayed growth and puberty in children: a shortage of normal red blood cells causes a slow growth rate. This is why adults who have sickle cell disease are often slender or smaller in size than other adults.

Hand-Foot Syndrome: this is when sickled cells block the blood vessels in the hands and feet of young children (usually under age 4). It can lead to swelling on the back of the hands and feet and progresses into the fingers and toes. It may also lead to pain and fever.

Vision loss: this occurs when the blood vessels in the eye become blocked with sickle cells and the retina- a part of the eye- becomes damaged. This can result in blindness.

Kidney damage and loss of body water in the urine

Leg ulcers

Bone damage

Multiple organ failure

Bossed skull (a square shaped skull)

Oral and dental abnormalities

Any and all major organs of the body are affected by sickle cell disease as a result of the abnormal functioning of the sickled cells and their inability to flow through the small blood vessels correctly. This causes excruciating pain and gradual degeneration (deterioration and loss of function in tissues, cells, and organs).

Sickle cell warriors are also prone to many other complications due to the stickiness of the sickled red blood cells, which coagulate (i.e. clump together) forming blood clots in a deep vein (Deep Vein Thrombosis- DVT) or in the lung (Pulmonary Embolism- PE). DVT and PE can cause serious illness, disability, and in some cases, death. Other possible occurrences include miscarriage, complications during pregnancy and childbirth; and low sperm count or infertility in males.

A sickle cell warrior may only experience some of the above symptoms. However all warriors suffer anemia, pain crises and jaundice/yellowing.

Diagnosis of Sickle Cell Disease

In addition to a doctor taking a person’s complete medical history and carrying out a physical examination, the following blood tests are also used in diagnosing SCD:

Chorionic villus sampling– a blood test that can be performed from 9 weeks of pregnancy to test the unborn baby for the disease

Electrophoresis– a blood test that is used to determine if a person is a sickle cell carrier or if they have the disease

Treatment of Sickle Cell Disease

Drinking 8 to 10 glasses of water a day – to prevent dehydration
Pain medications
Folic acid – to help prevent severe anemia
Hydroxyurea– a recently found medication that has been very successfully used to reduce the frequency of pain crises and reduce the need for frequent blood transfusions in warriors
Vaccinations and Antibiotics – to prevent and treat infections
Blood transfusions – to treat anemia, prevent stroke, and dilute sickled blood cells with normal blood cells in order to treat pain and other complications
Regular eye exams– to screen for retinopathy (eye damage)
Hepatitis C screening– to test for Hepatitis C in warriors who receive blood transfusions
Transcranial doppler ultrasound (TCD scanning) – to screen for stroke risk by examining blood circulation within the brain
Stem cell transplant – this is the only cure for symptoms. However, it is expensive, risky and may result in many complications including death. It can cure the sickle cell warrior of symptoms however he or she will still be able to pass on the sickle cell gene to their offspring.
Prevention

If you have sickle cell disease or if you are a carrier, procreating with a non-carrier (AA) is the most efficient way of ensuring that none of your children has the disease.

If you plan on having a child with a potential partner, it is advisable that you both go for genetic counseling and blood testing so as to determine your sickle cell statuses.

If you or a loved one suffers from sickle cell disease, there are resources available to you on the internet; you can also visit your local hospital, find a hematologist (blood doctor), join a sickle cell support group, or attend family therapy and/or genetic counseling.

Resources available

An online global support group:
http://www.sicklecellsupportgroup.org

Sickle Cell Foundation Nigeria
National Sicklecell Centre,

Opposite LUTH on Ishaga Road, Idi Araba,

Lagos, Nigeria

(+234) 0803 584 6666

(+234) 1- 7253987

info@sicklecellfoundation.com

scf.nig@gmail.com

www.sicklecellfoundation.com

The National Sicklecell Centre provides services such as: genetic counseling, a sickle cell clinic with free drugs and equipment, prenatal diagnosis, newborn screening, TCD scanning of children to determine risk of stroke, and a wealth of educational materials including an e-library on SCD.

Please visit their website for more information.

Did you know that there are different types of sickle cell disease?

Sickle cell SS is the most common type of sickle cell disease accounting for 65% of cases in black people.

There are however other types of sickle cell disease including Sickle cell SCwhich accounts for 25% of cases; Sickle beta thalassemia; Sickle cell SE; Sickle cell SD and Sickle Cell SO

You can learn more about each of these in a future post. Until then, stay healthy and God bless!

Written by Towoju Paul-Lawal

B.A. (Psych)

[Concentration in P.Medicine]

Sources:

http://www.ncbi.ndlm.nih.gov

http://www.childrenshospital.vanderbilt.org

http://www.gov.uk

http://www.who.int