Can You Pass Severe Sickle Cell Disease if You Have S-HPFH?

Yes, a person with S-HPFH can pass severe sickle cell disease to their child. However, this only happens if their partner also carries the sickle cell gene or another hemoglobin trait. The risk of your child having severe sickle cell disease depends entirely on your partner’s genetic status ^[1][2].

Understanding the Genetics of S-HPFH

To understand how this works, it helps to look at the genes involved. S-HPFH is what doctors call a compound heterozygous condition ^[1][3]. This simply means you inherited two different hemoglobin genes, one from each of your parents:

• One sickle cell gene (HbS) ^[4]
• One Hereditary Persistence of Fetal Hemoglobin (HPFH) gene ^[3]

When you have a child, you do not pass on your exact condition. Instead, you will pass on only one of these two genes ^[4]. For every pregnancy, you have a 50% chance of passing on the sickle cell gene, and a 50% chance of passing on the HPFH gene.

Why Partner Testing is Crucial

Because you carry one sickle cell gene, your partner’s genetics are the deciding factor in whether your child will have severe sickle cell disease ^[5]. This is why partner testing is an absolutely essential part of family planning.

Depending on your partner’s test results, here is what could happen:

• If your partner has normal hemoglobin (HbAA): Your child cannot have severe sickle cell disease. They will either inherit the sickle cell trait (if you pass your S gene) or the HPFH trait (if you pass your HPFH gene). Neither of these traits causes severe disease, though your child will need to know their status for their own family planning in the future.
• If your partner has the sickle cell trait (HbAS): There is a risk. For each pregnancy, there are four possible outcomes based on which genes are passed down:
  • 25% chance of HbSS (severe sickle cell anemia) - inheriting your S gene and your partner’s S gene ^[5][6].
  • 25% chance of S-HPFH (your mild condition) - inheriting your HPFH gene and your partner’s S gene.
  • 25% chance of sickle cell trait (HbAS) - inheriting your S gene and your partner’s normal A gene.
  • 25% chance of HPFH trait - inheriting your HPFH gene and your partner’s normal A gene.
• If your partner has another hemoglobin trait: If your partner carries a different trait, such as hemoglobin C or beta-thalassemia, your child could also be born with other forms of sickle cell disease if they inherit your sickle cell gene ^[5][7].

Here is a visual breakdown of the genetic outcomes if your partner has the sickle cell trait (HbAS):

Why HbSS is More Severe Than S-HPFH

You might wonder why a child with HbSS would have a severe disease when your own S-HPFH is mild.

Your condition is usually very mild because the HPFH gene tells your body to keep producing high levels of fetal hemoglobin well into adulthood ^[1][8]. This fetal hemoglobin acts as a powerful shield, preventing your red blood cells from sickling and protecting you from severe symptoms ^[9][10].

If your child inherits two sickle cell genes (HbSS), it means they inherited your sickle cell gene rather than your HPFH gene ^[4]. Without that protective HPFH gene ^[11], their body will not produce the high levels of fetal hemoglobin needed to stop the sickling process, leading to the severe symptoms associated with classic sickle cell anemia ^[1].

Next Steps for Family Planning

If you have S-HPFH and are planning to have a child, here are the most important steps you can take:

• Request comprehensive screening for your partner: Your partner should undergo a specialized hemoglobin blood test (such as hemoglobin electrophoresis or high-performance liquid chromatography, often abbreviated as HPLC) before you try to conceive ^[12]. A routine complete blood count (CBC) is not detailed enough to detect all traits.
• Meet with a genetic counselor: A genetic professional can review your specific molecular diagnosis, as there are different types of HPFH mutations ^[7]. They can explain your exact risks and help you navigate your family planning options safely ^[12].
• Explore reproductive options: If your partner is found to be a carrier of a hemoglobin trait, a genetic counselor can also discuss advanced reproductive options ^[7]. For example, in vitro fertilization (IVF) with preimplantation genetic testing (PGT) allows doctors to test embryos for sickle cell disease before pregnancy, offering a way to prevent passing on the severe condition.