Sickle Cell Considerations in Athletes

Definition, frequency, and variation of sickle cell trait

SCT is not a disease but a condition, resulting from inheritance of one gene for sickle hemoglobin (S) and one gene for normal hemoglobin (A). The sickle gene is common in regions endemic with malaria, because SCT protects against early death from malaria, providing a procreation advantage to SCT carriers. SCT is found in about 8% of African American, 0.5% of Hispanic, and 0.2% of white individuals.² Each red blood cell in SCT typically has about 40% hemoglobin S. The co-inheritance of

Exertional sickling in athletes

The most vital clinical consideration for athletes with SCT is exertional sickling, because this “sudden-collapse” syndrome can be fatal. Despite increasing national focus on this problem, fatal cases continue to occur, as illustrated by the demise of a 20-year-old male student-athlete in August 2010 during a track tryout at a university in North Carolina.⁴ Other sickling collapses and deaths have occurred in various sports or exercises (Box 2), and have included male and female athletes, some

Lumbar paraspinal myonecrosis

Compartment syndrome of the lower extremity can present clinically with exertional sickling collapse syndrome, both in the military and in college football.36, 37 Recently, lumbar paraspinal myonecrosis, a new variant of compartment syndrome, has been associated with exertional sickling in football. Notably, this syndrome is not unique to football or to athletes with SCT. It has been reported in skiers and in a water-skier, yet we believe that it may occur more often in football players with

Splenic infarction

Exertional sickling was a newsmaker in the autumn 2009, when Pittsburgh Steelers safety Ryan Clark, who has SCT, was told by his coach to skip the game against the Broncos in the mile-high altitude of Denver.⁴⁰ After Clark played in Denver in 2005, he was diagnosed with a “splenic contusion.” Subsequently, he played in Denver in 2007, and suffered a sickling splenic infarction, developed an abscess in the necrotic spleen, and had splenectomy and cholecystectomy, which sidelined him for the

Hematuria and hyposthenuria

Gross hematuria is another complication of SCT, as described in a black junior college basketball player after a strenuous drill. Hematuria waxed and waned and resolved in 2 weeks. Past medical history had revealed a similar episode 5 years earlier. Intravenous pyelogram and cystoscopy results were normal and his hematuria was attributed to SCT.⁴⁷ The author has been queried about 2 other SCT athletes with gross hematuria, one a football player and the other a basketball player. In each case,

Venous thromboembolism

In a retrospective study of approximately 65,000 consecutively hospitalized black men, pulmonary embolism was found in 2.2% of those with SCT versus 1.5% of those with normal hemoglobin, a relative risk of about 1.5.⁵³ As the researchers noted, this result must be regarded with caution because the difference was small and surrogate markers were used for the diagnosis of pulmonary embolism.

A new study, however, seems to confirm this risk. In a case-control study that compared 515 hospitalized

Sickling hemoglobinopathies

Few, if any, athletes with sickle cell anemia are able to compete on teams either in high school or beyond. Accordingly, the foremost sickling hemoglobinopathies that concern athletes are hemoglobin SC, S-beta-thalassemia, and hemoglobin SE. All 3 tend to cause a mild or moderate anemia that limits athletic stamina, along with other sickling problems, including occasional painful sickling crises and various splenic syndromes, especially at high altitudes or on plane flights. On first

Summary

The foremost among sickle cell considerations in athletes is SCT, which can pose a range of clinical problems. The vital concern is exertional sickling collapse, which can be fatal, occurs in a variety of sports, and is a leading cause of death in college football. The chronology of sickling pathophysiology parallels the timing of exertional collapse. Recent research sheds light on the microcirculatory problems and adaptations in athletes with SCT. Sickling collapse is an “intensity”-associated