Sickle Cell Disease (SCD) Program

1. Sickle Cell Trait (SCT):
   -  A person who inherits one sickle cell gene (hemoglobin S) and one normal gene (hemoglobin A) has sickle cell trait.
   -  People with sickle cell trait are usually asymptomatic but can pass the sickle cell gene to their children.
2. Sickle Cell Disease (SCD):
   -  A person with sickle cell disease inherits two sickle cell genes (one from each parent).
   -  This condition can lead to serious health problems like pain crises, anemia, and organ damage.

How Inheritance Works
The inheritance of sickle cell follows the principles of autosomal recessive inheritance, which means both parents must carry the sickle cell gene for a child to inherit the disease. Here are the possible gene combinations:

When Both Parents Have Sickle Cell Trait (SCT):
If both parents have sickle cell trait (each with one sickle cell gene and one normal gene), there are four possible genetic combinations for their child:

• 1 in 4 chance (25%) the child inherits two normal genes (normal).
• 1 in 4 chance (25%) the child inherits two sickle cell genes (sickle cell disease).
• 2 in 4 chance (50%) the child inherits one normal gene and one sickle cell gene (sickle cell trait).

When One Parent Has Sickle Cell Trait (SCT) and the Other Parent Has Normal Genes: If one parent has sickle cell trait and the other is completely normal (not carrying the sickle cell gene), each child has:

• 50% chance of inheriting a normal gene and being normal.
• 50% chance of inheriting one sickle cell gene (sickle cell trait).

In this case, the child can't inherit sickle cell disease because there is no chance of inheriting two sickle cell genes.

Key Points:

• Sickle Cell Trait (SCT) means you carry one sickle cell gene and one normal gene, but usually don't have symptoms.
• Sickle Cell Disease (SCD) means you inherit two sickle cell genes (one from each parent).
• Sickle cell disease or trait is passed from parent to child at conception; it cannot develop later in life.
• Both parents must have the sickle cell gene to pass it on to their child with a chance of having sickle cell disease.

Understanding these inheritance patterns is crucial for individuals with sickle cell trait or disease to make informed decisions about family planning and the potential risks to their children.

In individuals with sickle cell disease, both copies of the HBB gene (one from each parent) are mutated, leading to the exclusive production of hemoglobin S. On the other hand, individuals with sickle cell trait carry one normal HBB gene and one mutated one, so they produce a mix of normal hemoglobin (HbA) and hemoglobin S.

Other variations of sickle cell disease occur when one mutated HBB gene produces hemoglobin S, and the other produces a different abnormal hemoglobin. For example, in sickle cell-hemoglobin C (HbSC) disease, people have both hemoglobin S and hemoglobin C in their red blood cells. When hemoglobin S combines with beta thalassemia mutations, the result is hemoglobin S-beta thalassemia (HbSBetaThal).