Sickle Cell Disease 2 Variant Health Care Discussion Guide
How do I talk to my health care provider about my Mayo Clinic GeneGuide™ results?
This test has indicated that you have two variants in the beta hemoglobin gene (HBB):
- This test only tests for the common variants in HBB – called Hb S and Hb C – which cause sickle cell disease.
- This test cannot be used to make a diagnosis of sickle cell disease.
- If this result is unexpected, you can use this guide as a starting point for your discussion with your health care provider.
Print a report to share with your health care provider.
How can a person inherit two variants for sickle cell disease?
When a person is found to have two variants in a gene, there are two possibilities:
- The two variants are on the same chromosome, or
- The two variants are on different chromosomes.
Two variants on different chromosomes
More commonly, a person has one HBB variant on each chromosome, (called trans, meaning across). Remember, chromosomes come in pairs. In this case, both HBB genes carry a variant. This person might have sickle cell disease, which could range from no symptoms to severe symptoms, depending on which variants are present. When a person has two sickle cell variants (either Hb S or Hb C), the variants will always be in trans.
Two variants on the same chromosome
Less commonly, a person has two HBB variants on the same chromosome (called cis, meaning same side). In this case, the HBB gene on one chromosome has two variants (either Hb S or Hb C along with a variant in another part of the HBB gene). The HBB gene on the other chromosome has no variants. This person is considered a carrier. Learn more about carrier screening
How are two variants passed on to children?
Variants in trans: A person with two variants on separate chromosomes (in trans) will pass on one variant to each of their children. If their partner is not a carrier for a variant in HBB, each child will be a carrier for an Hb S or Hb C variant (depending on what they inherit).
If their partner is a carrier for Hb S or Hb C, each child has a 50 percent (1 in 2) chance of being a carrier and a 50 percent (1 in 2) chance of being affected with sickle cell disease or a milder type of hemoglobinopathy (Hemoglobin C disease), depending on what variants he or she inherits.
Variants in cis: If a person has two variants on the same chromosome (in cis), each child has a 50 percent (1 in 2) chance of inheriting both variants and a 50 percent (1 in 2) chance of inheriting no variants. If their partner is not a carrier, each child has a 50 percent (1 in 2) chance of being a carrier.
If their partner is a carrier, each child has a 25 percent (1 in 4) chance of being affected with a sickle cell disease.
What steps might my health care provider take based on the test results?
For individuals with 2 HBB variants, a health care provider might consider further testing for hemoglobinopathies, such as a hemoglobin electrophoresis and a complete blood count.
Talk to your health care provider or a genetic counselor about next steps.
What other resources exist for information about diagnosis and treatment of hemoglobinopathies?
If you don't have access to a local health care provider or would prefer to discuss this result before scheduling an appointment you can:
- Contact the Mayo Clinic GeneGuide™ product service team using the Contact Form.