Sickle cell HbSO is a form of sickle cell disease (SCD) that involves two different types of abnormal haemoglobin proteins. Haemoglobin is a protein contained in red blood cells that helps oxygen bind to red blood cells so that it can be carried throughout the body.
SCD refers to a group of genetic disorders that causes sickling of the red blood cells and many health complications as a result. While healthy red blood cells are normally round, sickling causes them to become shaped like a crescent moon and be sticky and hard.
SCD can be caused by a variety of abnormal haemoglobin proteins. Someone with HbSO has one copy of the haemoglobin gene that encodes for the haemoglobin “S” and one copy of the haemoglobin gene that encodes for the haemoglobin “O” protein. People with HbSO typically deal with many of the symptoms of SCD and have a high risk of complications due to the disease. HbSO is a very rare form of the disease.
The main symptoms of sickle cell HbSO include:
Many children are diagnosed with SCD as newborns, before they leave the hospital. If your child was not screened for SCD as a newborn and is showing symptoms, such as a fever, potential infection, or even signs of a stroke, take your child to the doctor right away.
Sickle cell HbSO is caused by a mutation in the gene that produces normal copies of the haemoglobin protein. This mutation causes the gene to tell the body to produce abnormal copies of haemoglobin. In the case of HbSO, one copy of the haemoglobin gene tells the body to produce haemoglobin protein “S” and the other copy of the haemoglobin gene tells the body to produce haemoglobin protein “O”.
Having parents with the haemoglobin “S” trait or the haemoglobin “O” trait is not a cause for HbSO, but it is a risk factor. In cases where one parent has the haemoglobin “O” trait and the other has the haemoglobin “S” trait, there is a 25% chance that a baby born to this couple will have HbSO. Other alternatives involve the child carrying just the haemoglobin “S” trait, just the haemoglobin “O” trait, or having completely normal haemoglobin traits.
Since genetics is such a risk factor for HbSO, people with abnormal haemoglobin traits or some form of SCD, including HbSO, may consider getting genetic screening done when trying to conceive.
Risk factors for HbSO include being of Arab descent.
Sickle cell HbSO may be diagnosed in newborns during a routine blood test. If you’re an older child or adult who was not diagnosed with sickle cell HbSO as a newborn that is now having symptoms, a doctor will use a combination of your medical history, symptoms, and a blood test to confirm your diagnosis.
Complications of sickle cell HbSO include sepsis, meningitis, recurring infection, acute chest syndrome, organ failure, and death.
HbSO prevents very similarly to HbSS, the most prevalent and severe form of SCD. It is treated similarly for this reason. Treatment is aimed at managing symptoms and complications. The main medication people with HbSO take is hydroxyurea, which can manage acute symptoms like pain crises and acute chest syndrome. The only cure is bone marrow transplantation.