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Sickle Cell Disease

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Other Names

  • Sickle Cell Trait
  • Sickle Cell Crisis
  • Exertional Sickling
  • Sickling Collapse
  • Lumbar Paraspinal Myonecrosis
  • Splenic Syndrome
  • Splenic Infarction


  • This page refers to athletes with both sickle cell disease (SCD) and sickle cell trait (SCT)


  • SCT prevalence[1]
    • 8% of African Americans
    • 0.5% Hispanic
    • 0.2% White


  • Sickle cell trait (SCT)
    • Inheritance of one gene for sickle hemoglobin (S) and one for normal hemoglobin (A)
    • SCT protects against malaria, giving a reproductive advantage to carriers in sub-saharan africa
    • Each red blood cell (RBC) is about 40% hemoglobin S
    • Co-inheritance of alpha thalassemia trait can lower the amount of hemoglobin S (occurs in about 1/3 of african americans)

Exertional Sickling


  • Most vital clinical consideration in athletes with SCT because it can be fatal
  • Athletes have died in football, basketball, cross-country, track and field, boxing and recreational swimming
  • It is the most common cause of death in NCAA Division-1 football (need citation)
    • From 2000-2010, all of these deaths occurred during training and conditioning (none during games)
  • Part of the reason for NCCAA mandated SCT screening in college athletes[2]
  • This phenomenon is also documented among military recruits first noted in 1970[3]
    • 4 recruits died, one apparently of coronary heart disease
    • The other 3 fit a pattern: collapse during running, hypotension, metabolic acidosis, hyperkalemia, disseminated intravascular coagulation (DIC), oliguria, and “sudden” death 8 to 25 hours after the collapse.
  • The US Armed Forces performed a study of all recruits from 1977-1981[4]
    • The risk of unexplained sudden death in black recruits with SCT was 40 times higher than in all other recruits
    • They also found that exercise-related death in black recruits with SCT was 30 times more common than in black recruits without SCT
    • Exertional heat illness was often cited as initiating hemostatic dysfunction
  • 6 deaths occurred between 1992 and 2001[5]
  • One army study looked at 30 exercise collapses of recruits with SCT (need citation)
    • The researchers concluded that exertional heat illness was the cause in 22
    • However, most had core temperature below 102 or no temperature recorded at all
  • Another army study reviewed cases of exertional rhabdomyolysis[6]
    • The authors concluded that the main cause of death is "explosive" rhabdomyolysis including hyperkalemia, lactic acidosis, hypocalcemia
    • The risk of rhabdomylosis in recruits with SCT was increased nearly 200-fold
    • They cited more often than not sustained maximal exertion rather than exertional heat illness as the cause

Exercise Intensity

  • Sickling collapse can occur year round
  • Typical exercise stimulus is maximal exertion sustained for at least a few minutes[7]
    • Can occur from as little sprint distance of only 600 - 1200 m (need citation)
    • Can also be due to an abrupt increase in training intensity, training at unfamiliar altitude or return to sport with suboptimal physical conditioning
  • Of the 10 Division-1 football players who died between 2000 and 2010
    • 5 had been performing serial sprints for 5 to 30 minutes
    • 4 had been performing fast-tempo, multi-station drills, with little or no rest between stations for 12-60 minutes


  • Degree and duration of exertion appear to predict sickling collapse
  • Research in non-SCT patients has shown that 1-5 minutes of cycling can induce severe hypoxemia, lactic acidosis[8]
  • Dehydration can increase exertional sickling[9]
  • 4 factors are currently thought to contribute: profound hypoxemia, lactic acidosis, hyperosmolarity, and red cell dehydration

Clinical Features

  • Difficult to distinguish from other more common causes of exertional collapse
  • History
    • Leg or low back pain, weakness
    • Body cramps
    • "jello legs" or "my legs wont go"
    • Athletes will slump to the ground or sudden fall or hobble
  • Physical exam
    • Weakness exceeds degree of pain
    • No evidence of muscle cramping clinically
    • Initially lucid and communicative but may have a decline in cognition
    • Tachypnea but with clear lungs (from metabolic acidosis)
    • Core temperature typically less than 103

Screening for SCT

  • Controversial
  • Army does not currently screen
  • All 50 states screen newborns
  • NCAA screens all division 1 athletes


  • This a medical emergency and should be treated as such
  • Check vital signs including core temperature
  • Provide supplemental O2 (if even not hypoxic)
  • Cool patient if hyperthermic
  • Begin IV hydration
  • If not immediate improvement, transfer to hospital via EMS
  • Anticipate clinical decline and know where AED is
  • Communicate with emergency department about sickle cell rhabdomyolysis


  • Allow athletes to set their "own pace"[10]
  • Gradual build up in training rather than aggressive increase
  • No extreme performance tests
  • Adjust for heat, altitude
  • Control chronic illnesses including asthma
  • Maintain adequate hydration
  • Disqualify athletes from training if ill

Compartment Syndrome

  • Can occur in lower extremities as seen in non-SCT athletes
  • Lumbar Paraspinal Myonecrosis[11]
    • Atypical form of acute compartment syndrome in SCT athletes
    • Patients complain of acute low back pain with prolonged symptoms for 1-2 weeks
    • CK is elevated
    • CT and/or MRI is abnormal, shows muscle damage, myonecrosis
    • Athletes often able to return to play with modification

Splenic Infarction

  • Sometimes referred to as splenic syndrome
  • Often associated with exercise at altitude
    • Risk thought to begin at 5000 ft, increases at higher altitudes[12]
  • Famous case of Ryan Clark, former safety for the Pittsburg Steelers[13]
    • Played at elevation (Denver, CO) in 2005 and diagnosed with "splenic contusion"
    • Played again in 2007 and suffered a splenic infarction, including an abscess requiring splenectomy and cholecystectomy


  • Overall, rare and occurs in fewer than 5% of patients with SCT (need citation)
  • Case reports of hematuria attributed to SCT[14]
    • Somewhat a diagnosis of exclusion after normal IV pyelogram and cystoscopy
  • Results from sickling deep within the renal medulla[15]
    • Ocassionally associated with papillary necrosis
    • 80% from left kidney
  • Treatment is generally conservative and includes
    • Relative rest
    • Hydration
    • Iron supplementation as needed
  • For progressive or persistent hematuria, can consider
    • Vasopressin
    • Amino caproic acid
    • Efficacy of these agents is unknown
  • Hyposthenuria is the inability to concentrate urine
    • Occurs in SCT due to altered blood flow to the renal medulla
    • Clinical Significance is unknown

Venous Thromboembolism (VTE)

  • See: Pulmonary Embolism
  • SCT increases the relative risk of pulmonary embolism by 1.5 - 2.0[16][17]
    • For reasons that are less clear, the risk of DVT may not be as great

Risk Factors

Differential Diagnosis

Clinical Features






Rehab and Return to Play


Return to Play


See Also


  1. Bonham VL, Dover GJ, Brody LC. Screening student athletes for sickle cell trait—a social and clinical experiment. N Engl J Med 2010;363:997–9.
  2. Bonham VL, Dover GJ, Brody LC. Screening student athletes for sickle cell trait—a social and clinical experiment. N Engl J Med 2010;363:997–9.
  3. Jones SR, Binder RA. Sudden death in sickle-cell trait. N Engl J Med 1970;282: 323–5.
  4. Kark JA, Posey DM, Schumacher HR. Sickle-cell trait as a risk factor for sudden death in physical training. N Engl J Med 1987;317:781–7.
  5. Scoville SL. Recruit mortality. In: DeKoning BL, editor. Recruit medicine. Washington, DC: Defense Department, Army, Borden Institute. Walter Reed Army Medical Center; 2006. p. 519–53.
  6. Gardner JW, Kark JA. Fatal rhabdomyolysis presenting as mild heat illness in military training. Mil Med 1994;159:160–3.
  7. Eichner ER. Sickle cell trait in sports. Curr Sports Med Rep 2010;9:347–51.
  8. Osnes J-B, Hermansen L. Acid-base balance after maximal exercise of short duration. J Appl Physiol 1972;32:59–62.
  9. Bergeron MF, Cannon JG, Hall EL, et al. Erythrocyte sickling during exercise and thermal stress. Clin J Sport Med 2004;14:354–6.
  10. Eichner ER. Sickle cell considerations in athletes. Clin Sports Med. 2011 Jul;30(3):537-49.
  11. Schnebel B, Eichner ER, Anderson S, et al. Sickle cell trait and lumbar myonecrosis as a cause of low back pain in athletes. Med Sci Sports Exerc 2008; 40(Suppl 5):537a.
  12. Lane PA, Githens JH. Splenic syndrome at mountain altitudes in sickle cell trait. Its occurrence in nonblack persons. JAMA 1985;253:2251–4.
  13. Eichner ER. Exertional sickling. Curr Sports Med Rep 2010;9:3–4.
  14. Eichner ER. Hematuria—a diagnostic challenge. Phys Sportsmed 1990;18(11): 53–63.
  15. Ataga KI, Orringer EP. Renal abnormalities in sickle cell disease. Am J Hematol 2000;63:205–21.
  16. Heller P, Best WR, Nelson RB, et al. Clinical implications of sickle-cell trait and glucose-6-phosphate dehydrogenase deficiency in hospitalized black male patients. N Engl J Med 1979;300:1001–5.
  17. Austin H, Key NS, Benson JM, et al. Sickle cell trait and the risk of venous thromboembolism among blacks. Blood 2007;110:908–12.
Created by:
John Kiel on 13 June 2019 10:20:21
Last edited:
1 February 2020 15:07:31