Sickle cell disease

Red blood cells are normally soft and round, and they bend to squeeze through the smallest vessels. In sickle cell disease an inherited change in haemoglobin, the protein that carries oxygen, makes the cells stiff and curved like a sickle. They catch in small vessels, cutting off the blood supply and causing pain, and they break down after a few weeks instead of a few months, causing anaemia.

The condition is present from birth and lasts for life. In India it is found across several states and is more common in some communities of central India, including parts of Maharashtra, Madhya Pradesh and Chhattisgarh, and particularly among tribal populations. A national programme now offers screening and counselling in these areas.

Symptoms usually begin in the first year of life, once the baby's protective haemoglobin has been replaced.

• Episodes of sudden severe pain, in the bones, back, chest or tummy, lasting hours to days
• Painful swelling of the hands and feet in babies and toddlers
• Tiredness, breathlessness and paleness from long-standing anaemia
• Yellow eyes or skin, because red cells are breaking down
• Frequent or severe infections
• Slower growth and later puberty in children
• Leg ulcers, usually around the ankle, in older children and adults

How severe the disease is varies a great deal, even between brothers and sisters. Some people have frequent crises; others go long stretches feeling well.

Make an appointment in the next few days if pain episodes are becoming more frequent, if tiredness is worsening, if a leg ulcer is not healing, if vaccinations or daily medicines have lapsed, or if you are planning a pregnancy or a marriage where sickle cell runs in either family.

The cause is a change in the gene for haemoglobin, producing haemoglobin S. A child who inherits a sickle gene from both parents has sickle cell disease. A child who inherits one sickle gene and one usual gene has sickle cell trait and is generally healthy.

When both parents carry the trait, every pregnancy carries a one in four chance of a child with the disease, a two in four chance of a child with the trait, and a one in four chance of a child with neither. Related conditions occur when a sickle gene is inherited alongside a different abnormal haemoglobin, such as in sickle beta thalassaemia.

The disease itself is inherited, so the only risk factor for having it is the parents' genes. Separate from that, certain things make a crisis more likely in someone who already has the condition:

• Both parents carrying the sickle gene
• Family origins in a community or region where sickle cell is common
• Dehydration, and hot weather with too little to drink
• Cold, wind, and getting wet or chilled
• Infections, including malaria and chest infections
• Heavy exertion, or exercise without enough fluids
• Travel to high altitude, or unpressurised flights
• Stress, and tobacco or alcohol use

Blocked vessels and constant anaemia can affect almost any organ. The serious complications include acute chest syndrome, where chest pain, fever and breathlessness signal a dangerous problem in the lungs, and stroke, which can happen even in young children.

• Severe infections, because the spleen stops working properly
• Sudden worsening anaemia, including blood pooling in an enlarged spleen in young children
• Gallstones, from the constant breakdown of red cells
• Damage to the kidneys, the eyes, the hips and the lungs over time
• A painful erection lasting hours, which can damage the tissue if not treated quickly
• Leg ulcers, delayed growth and delayed puberty
• Higher risks during pregnancy, for both mother and baby

The disease cannot be prevented in a person who has it, but crises and complications largely can be, and families can find out their risk before a child is conceived.

• A blood test for sickle cell before marriage or pregnancy, especially where the condition is common in the community
• Counselling for couples where both partners carry the trait
• Newborn and childhood screening, so treatment starts before the first crisis
• Daily antibiotics through early childhood, as prescribed, and every recommended vaccination
• Drinking plenty of fluids, and more in hot weather or during exertion
• Keeping warm, avoiding sudden cold and staying dry
• Folic acid as prescribed, and prompt treatment of any fever or infection
• Avoiding tobacco and alcohol

A blood test identifies the type of haemoglobin present and tells the disease, the trait and the normal pattern apart. Simple point of care tests are used in screening camps, with a laboratory test to confirm. A full blood count shows the degree of anaemia.

Testing can be done at any age, and is offered to newborns, to children and adults in areas where sickle cell is common, and to couples before marriage or during pregnancy. Testing during pregnancy can tell whether the baby is affected.

Day to day care aims to prevent crises and to pick up complications early. It includes folic acid, daily antibiotics in childhood, a full set of vaccinations, regular clinic reviews, and eye and other checks as the years go on.

• Pain relief, from simple medicines at home to strong pain relief and fluids given in hospital
• Hydroxycarbamide, a medicine that makes crises and chest problems less frequent in many people
• Blood transfusions, for severe anaemia, acute chest syndrome, or to prevent stroke
• Antibiotics at once for any fever, before the cause is known
• Treatment of complications such as gallstones, leg ulcers and hip problems
• A stem cell or bone marrow transplant, which can cure the disease but is suitable for only a few people

Newer treatments, including gene therapy, exist in some centres. Whether any of them fits a particular person is a discussion for the specialist team.