Considerations in the athlete with Sickle cell Trait.
Sickle cell anemia (SCD) is a hereditary disease of the red blood cells affecting in the USA, African-Americans, Hispanic of Caribbean ancestry. A normal red blood cell is round but in people suffering from this disease the red blood cell becomes defective and change its shape. A faulty hemoglobin is responsible of the changes. This hemoglobin is called Hemoglobin “S”, (HgbS) which replaces the normal Hemoglobin “A”, (HgbA). During their short lifetime, the red blood cells become rigid and deformed like crescent moons or sickles.
Up to recently, this condition has shown no cure, but treatments have existed to help pain and avoid premature death and infections. Recently blood transfusion and bone marrow transplantation have already claimed victory in the treatment of this disease. More, Gene therapy to correct the genetic abnormalities is being studied. We will today discuss the athletes involved in competitive sports suffering of this disease while only caring the “sickle cell trait”. I remember well during my residency training, discussions held by our teachers at Howard University Hospital, on a 32-year-old patient, asymptomatic who presented to the ER with a massive hematuria. It was a puzzle, because this was never described in any known textbook, on a patient with the “Trait”.
We have learned with time that a proper hydration is necessary to avoid any painful crisis when the sickle shaped red blood cells clog the blood vessels, cutting off the blood supply to vital tissues and organs. The spleen is known as the first organ of defense responsible for trapping the deformed cells but it finally auto-scleroses and become inefficient in preforming its duty. Unfortunately, the body can’t replace those trapped and deformed cells enough to allow an effective transport of the Oxygen. As a result, the body lack in red blood cells and develop an Anemia.
In the United States 1/every 400 African-American birth and 1/1300 Hispanic of Caribbean descent will carry the disease. Children and young adults can die from the disease. Sickle cell disease is found around the world as well alone or in association with Thalassemia and infectious disease like Malaria among people of African. Italian, Turkish, Arabian, Greek, Southern Asian ancestry.
Often one will develop a mixture of normal and faulty hemoglobin in their red blood cells without the sickling phenomenon. This condition is called: The sickle cell Trait. It is estimated that 1/12 African-American carry the trait. They do not have sickle cell disease except in rare circumstances. The trait can be passed genetically from generation to generation. If two people have the trait, ¼ of the children (25%) may suffer from the disease (SCD). If only one parent carries the trait, 50% of the children will heritage from the trait but if one parent has the trait and the other one has the disease, it may not be recommended to have kids because 50% of them will have the disease.
The disease is passed on as part of the genetic makeup and I will not extend much on the complications related to painful sickle cells crisis, hand and foot syndrome in the infants. life-threatening infections, anemia, joint destruction and chondrolysis.
We will expand on the athlete with sickle cell trait, meaning the athlete who has received in his heritage one gene of normal hemoglobin and one gene of abnormal hemoglobin. The sickle cell trait differs from the sickle cell disease in the fact that there is a much lower concentration of sickled hemoglobin and when the intensity of activities increases, the local pH decreases while body temperature increases.
These conditions are encountered at higher concentration of hemoglobin lacking in Oxygen. The sickle cell trait patient usually remains asymptomatic because of his high ratio of normal hemoglobin. In extreme physical exertion, multiple case report in highly trained athletes or military personnel bought to light disastrous complications.
Rhabdomyolysis and sudden death caused by red blood cells sickling during athletic activities have been reported. There is a 10 to 30 times exercise-related death rate in the sickle cell trait athlete compared to non-carriers. A recent study on exertional sickling in NCAA Division I players has reported 16 deaths in which 10 of them were found related to exertional sickling. The other causes were due to cardiac (4), asthma (1) heat stroke (1). So, the majority (63%) of the athletes died from exertional sickling (10). Overall. The incidence remains underestimated because of lack of recognition of the sickle cell trait. Autopsies results have shown also patients with cardiomyopathy.
If we are living in a society where one African-American on 12 and one Caucasian on 2000, will have the sickle trait, you would believe that a more systematic search for this entity should be implemented by our healthcare specialists. More, this condition is prevalent in athletes whose ancestors come from Africa, the Caribbean regions as well as central and south America, the Mediterranean.
Exertional sickling is dangerous for those athletes because of the potential progression to rhabdomyolysis. In the athlete with a sickle cell trait, the sickling phenomenon occurs at the level of the muscle itself within the lumen of the supplying vessels. It creates a muscle necrosis and subsequently the release of breakdown products in the systemic circulation. Then a fatal cascade of events will follow with myoglobinuria and electrolyte imbalance quickly without any warning signs. Occasionally, muscle pain and weakness in the thighs, buttocks and back will be present. If such diagnosis is suspected during a game, these athletes need to be given close medical attention with immediate removal from play and fluid resuscitation to expand the intravascular volume and to increase the renal flow.
The myoglobin is responsible for the kidney damages but the intratubular obstruction with the epithelium toxicity contribute to the acute renal failure and electrolytes imbalance (High K and low Ca). This may require renal dialysis. The mortality rate can reach (20 %). Serious cardiac arrythmias and/or metabolic acidosis may complicate the picture.
Exertional sickling collapse is often confused with heat cramping and heat stroke, but we need to remember that exertional sickling is an ischemic process not solely a product of hyperthermia or/and lactic acidosis. These athlete core body temperatures are less than 105°F and often appear to be in less pain. Exertional sickling occurs quickly without any warning signs.
Rhabdomyolysis will be responsible for most of the sudden-death fatalities among the sickle cell trait population. There is enough evidence to suggest that asymptomatic and repeated exertional sickling may have long term effect on the renal function. With time, chronic renal damage may explain the higher death rate.
Nowadays, many professional organizations have already elected to screen their athletes for the sickle cell trait while it is mandatory to check your sickle cell status if you wish to highly compete in NCAA Division I. Many have also questioned the validity of such test instilling more harm than benefits. The Sickle cell Advisory Committee of the National Heart, Lung and Blood has urged to halt routine test on military recruits because of potential discrimination again the carriers.
In conclusion, Sickle cell Trait has become a well-recognized cause of sudden death among athletes and we wanted to discuss the signs which can help you recognize exertional sickling during physical exertion to avoid rhabdomyolysis and its complications.
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Maxime Coles MD