Sickle Cell Disease: Symptoms, complications and causes of this condition

Sickle Cell Disease: Symptoms, complications and causes of this condition
Sickle cell disease includes disorders such as sickle anaemia and thalassaemia, among others, depending upon which haemoglobin gene is abnormal in the person. @Shutterstock

Sickle cell disease includes disorders such as sickle anaemia and thalassaemia. Today, on the occasion of World Sickle Cell Day, let us see what this condition is all about.

Written by Mita Majumdar |Updated : June 23, 2022 11:27 AM IST

Sickle cell disease (SCD) is a common hereditary blood disorder in which, the otherwise, round, red blood cells look like sickles. Red blood cells have a molecule called haemoglobin that gives the red blood cell its colour, and which carries oxygen throughout the body. In a healthy person, haemoglobin is disc shaped, smooth, and flexible, allowing the red blood cells to flow easily through the blood stream. But in people with sickle cell disease, the haemoglobin proteins clump together and become shaped like rods, causing the red blood cells to become rigid and curved. These cells block the flow of blood, causing problems such as unexplained and sudden pain, swollen limbs, and poor vision among others. On 22nd December 2008, the United Nations General Assembly adopted a resolution that recognises sickle cell disease as a public health problem and "one of the world's foremost genetic diseases." Since then, every year, World Sickle Cell Day is observed around the world to raise awareness of sickle cell on June 19.

Sickle cell disease includes disorders such as sickle anaemia and thalassaemia, among others, depending upon which haemoglobin gene is abnormal in the person. Since the disorder is hereditary, it is present at birth, but most children show the signs and symptoms only after the age of 4-5 months. This is because all children are born with foetal haemoglobin that protects the red blood cells from sickling. When the babies with SCD are 4-5 months old, foetal haemoglobin is replaced by sickle cell haemoglobin (HbS). Today, on the occasion of World Sickle Cell Day, let us see what this condition is all about.


Signs and symptoms of sickle cell anemia, which vary from person to person and change over time, include:

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Red blood cells usually live for about four months and then they are replaced by new red blood cells. But sickle cells die in 10 to 20 days, much before new cells can be formed, leaving a shortage of red blood cells. And without enough red blood cells, your body can't get the oxygen, causing fatigue. You might also have shortness of breath, dizziness, and headaches.

Intense, unexplained pain

Episodes of pain, called pain crises, occur suddenly, out of nowhere, and are sharp, stabbing, and intense. Pain can occur wherever the sickle-shaped red blood cells block blood flow in the bloodstream; it can be your chest, abdomen, joints and even bones. The pain, lasting for a few hours to a few weeks. The frequency of pain varies from a few pain episodes in some people to a dozen or more crises a year in others. Severe pain episodes may require hospitalization.

Chronic pain

Sometimes, adolescents and adults with sickle cell anemia have chronic pain, which can result from bone and joint damage, ulcers and other causes. Chronic pain can be very severe significantly reducing the quality of life. Scientists are yet to understand its cause.

Painful swelling of hands and feet

Also called dactylitis, the swelling is caused by sickle-shaped red blood cells blocking blood flow to the hands and feet. Along with the pain, there may be coldness of hands and feet. This is usually one of the early signs of the disorder occurring in young children.

Frequent infections

Sickle cells can damage the spleen that fights infection, leaving you more vulnerable to infections.

Yellowish colour of the skin

Since a large number of red blood cells breakdown and cause low levels of circulating red blood cells, the skin becomes yellow in colour. Sometimes, the whites of the eyes also become yellowish. This is termed icterus.

Delayed growth

Red blood cells provide the body with the oxygen and nutrients needed for growth. A shortage of healthy red blood cells can slow growth in infants and children and delay puberty in teenagers.

Vision problems

Tiny blood vessels that supply your eyes may become plugged with sickle cells. This can damage the retina the portion of the eye that processes visual images, leading to vision problems.

See your doctor right away if you have or your child has unexplained episodes of severe pain in the abdomen, chest, bones or joints; yellowish skin or whites of the eyes; or, fever, as fever can be the first sign of an infection. Get immediate medical assistance if you notice one-sided paralysis or weakness in the face, arms or legs; confusion; trouble walking or talking; sudden vision problems or unexplained numbness.


In most people who have the genes for SCD, the episodes of pain can be triggered by illness, dehydration, stress, high altitude, and temperature changes.


Sickle cell anemia can lead to a host of complications. According to the Centers for Disease Control and Prevention, complications include

  • Acute chest syndrome, a life-threatening complication that causes chest pain, difficulty breathing, coughing, and fever.
  • Splenic sequestration, in which the sickle cells get trapped in the spleen and cause it to enlarge. Seek help if you suddenly feel weak, your heart beats faster, you have intense belly pain on the left side, and you feel extremely thirsty.
  • Vision loss, including blindness, because the sickle cells block the blood vessels in the eye and damage the retina.
  • Leg ulcers usually on the lower part of the leg, especially in boys/ men aged 10 years through the 50s.
  • Deep vein thrombosis and pulmonary embolism, when the sickle cells cause blood clots in the vein and lungs, respectively.
  • Kidney damage because of chronic deprivation of oxygen-rich blood to the kidneys. Renal involvement is usually more severe in sickle cell anaemia than in compound heterozygous types of SCD such as beta-thalassaemia and is typically mild sickle cell trait. Renal involvement contributes substantially to the diminished life expectancy of patients with SCD, accounting for 16 18% of mortality. [1]
  • Symptomatic stroke can occur in about 10 per cent of children with SCD. It can cause learning problems and lifelong disabilities.


Normally, the haemoglobin molecule picks up oxygen in the lungs and releases it when the red cells in the bloodstream reach the tissues such as muscles. However, it is different in case of sickle haemoglobin. After picking up the oxygen, sickle haemoglobin releases oxygen in the tissues, but, the molecules tend to stick together and form long chains or polymers. This is called polymerization. These rigid polymers distort the cell and cause it to bend out of shape. When the red cells return to the lungs and pick up oxygen again, the haemoglobin molecules become 'normal' again (depolymerization).

Taking into consideration that red cells circulate in the bloodstream four times in one minute, sickle haemoglobin undergoes repeated episodes of polymerization and depolymerization, which ultimately damages the haemoglobin and the red cell itself. This is called haemolysis.

Further, polymerization causes the iron-rich haeme component of haemoglobin to be released from the protein into the red cell membrane, causing the membrane to stiffen. The iron promotes the formation of very dangerous compounds, called reactive oxygen species or ROS, which again damage the red cells.

The bone marrow, where these red cells are produced, increase the production dramatically but is unable to keep pace with the destruction. The result is anaemia. [2]


  1. Nath KA, Hebbel RP. Sickle cell disease: renal manifestations and mechanisms. Nature reviews Nephrology. 2015;11(3):161-171. doi:10.1038/nrneph.2015.8.
  2. Bridges, KR. How Does Sickle Cell Cause Disease? 2002. Sickle.bwh.harvard.edu.