There are two separate conditions: Sickle Cell Disease (SCD), and Sickle Cell Trait. Both are genetic. “Disease” occurs when you inherit two copies of the responsible abnormal gene, one from each parent; “Trait” exists when you only get one copy (from just one parent). SCD is debilitating, but somewhat rare; Trait is common, and practically harmless.
The genetic abnormality in SCD makes our nice, round Red Blood Cells (RBCs) turn sickle-shaped. Then, two things can happen, not always at the same time. For one, RBCs break apart & dissolve, called “hemolysis,” which is just like losing blood Anemia). Also, for reasons that are not completely clear, blood vessels in various organs can go into spasm, which cuts off their circulation.
Sickle Cell is most common among Africans, and next so people of African descent (in the US, UK, Caribbean, etc.). The gene is also present to a much lesser degree in Latino, Mediterranean, and Middle-Eastern ethnicities.
SCD first shows itself in early childhood. There are an enormous variety of possible symptoms and complications, including:
- Serious bacterial infections
- Acute episodes of severe pain (sometimes called a “crisis”), in chest, abdomen, back, arms, or legs (or fingers / toes)
- Stroke / Seizures
- Priapism (a sudden erection that won’t go away, leading to impotence)
- Visual Loss
- Leg Ulcers
- Eventual serious damage to kidneys, lungs, liver, bones, heart, eyes, etc.
- Chronic pain and Depression
Milder forms of SCD exist, when one Sickle Cell gene combines with genes from other inherited diseases of the RBC, like Thalassemia. Years ago, most people with SCD died in childhood. Today, with good care by a specialist, people may live into their 60s or even 70s.
Both SCD and Trait can be easily diagnosed by blood tests for the type of hemoglobin in our RBCs (not the routine test for anemia. It is now standard to perform these on all babies at birth (fewer diagnoses were made earlier, when only African-American babies were tested). Adults can also get tested, such as immigrants from high-prevalence areas who were not tested at birth, or anyone who never found out their results (even though all parents are always told if their baby is positive for SCD, this doesn’t always happen for babies with Trait).
Sickle Cell Trait is not a disease, because people with it almost never become ill. They have a normal life expectancy. In the U.S., 7% to 10% of African-Americans have one sickle cell gene, meaning they have Trait. There are two main concerns:
- If both mother and father have Trait, there is a 25% chance that their baby will have actual Sickle Cell Disease.
- There are rare serious or life-threatening conditions that may occur among persons with Trait who are suddenly exposed to high altitude (without gradual acclimatization), become dehydrated in severe heat, have blood in urine, get hit in the eye, or possibly if they engage in intensive strenuous exercise.
When a man and woman planning to get pregnant both have Trait, it’s essential for them to receive good, professional genetic counseling. There are ways to test if the fetus has SCD. Decisions all involve personal attitudes toward abortion.
It’s controversial whether athletes should have mandatory testing for Trait. The danger is discrimination in sports, insurance, jobs, etc. The NCAA requires it for Division 1 & 2 sports. Military branches have their own different policies. All professional medical societies recommend against it, and instead recommend universal precautions for everyone, such as avoiding dehydration (especially in hot weather), gradual build-up in conditioning, don’t use stimulants, and prompt rest & medical attention for anyone struggling during exercise.