A 6-week-old boy is referred to a pediatric hematologist-oncologist for further evaluation following an abnormal newborn hemoglobinopathy screening. The father’s brother died of sickle cell anemia at an early age. Parental studies reveal that both mother and father are carriers of the sickle cell gene. The patient's temperature is 98.6°F (37.0°C), blood pressure is 80/45 mmHg, pulse is 130/min, and respirations are 25/min. The physician decides to repeat testing for the patient and his 3-year-old sister. The results are shown in Figure A. The physician begins counseling the family. Which of the following is the most likely complication that the patient may have in the future?
Stroke
Hematuria
Splenectomy
Infection
Hematuria
Based on the presence of both hemoglobin (Hb) A and S on gel electrophoresis, this patient has sickle cell trait. Episodes of painless hematuria are commonly seen in these patients.

Sickle cell trait is a condition that refers to carrying 1 normal and 1 abnormal beta-globin allele. On electrophoresis, this will present as 3 different bands consisting of about 50-60% HbA, 35-45% HbS, and < 2% HbF (fetal hemoglobin). HbF decreases significantly after the first 6 weeks of life. Individuals with sickle cell trait tend to be asymptomatic and do not have a decreased lifespan compared to the general population. However, they are at higher risk of some conditions. Patients are at increased risk of rhabdomyolysis during strenuous physical activity and may have episodic painless hematuria due to renal papillary necrosis. The hyperosmolar, acidotic, and hypoxic environment of the renal medulla is thought to trigger red cell sickling which results in ischemia and subsequent hematuria. Patients with sickle cell trait are managed similarly to the general population. These patients should receive reproductive counseling and use appropriate preventive measures to prevent dehydration during intensive exercise.

Hulsizer et al. studied the association between sickle cell trait and common medical conditions using insurance claims data. The authors found that sickle cell trait is associated with increased risks of diabetes, hypertension, heart disease, chronic kidney disease, and retinopathy. The authors recommend further evaluation of these associations using prospective studies derived from clinical data.

Figure/Illustration A shows gel electrophoresis with an example of a normal (95-98% HbA and < 2% HbF), sickle cell trait (50-60% HbA, 35-45% HbS, and < 2% HbF), and sickle cell anemia (85-95% HbS and 5-15% HbF) patient from left to right.

Incorrect Answers:
Answer A: Diabetes has not been associated with sickle cell trait in the majority of studies.

Answer C: Infection is a complication of sickle cell anemia. Mechanisms include functional asplenism, reduced tissue perfusion during a sickle crisis, and chronic transfusions with an indwelling catheter. Common infections include bacteremia, meningitis, and pneumonia due to Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitis. Sickle cell trait is not clearly associated with an increased risk of infection and actually confers some protection against malaria.

Answer D: Splenectomy from auto-infarction is often seen in sickle cell anemia, but it is rare with sickle cell trait. In sickle cell anemia, splenic sequestration of sickled red blood cells causes infarction, leading to progressive atrophy and functional hyposplenism. Most individuals with sickle cell disease are functionally asplenic by age 2 to 4. The spleen subsequently cannot phagocytose encapsulated organisms properly, which predisposes sickle cell patients to infection.

Answer E: Stroke is a complication of sickle cell anemia but not sickle cell trait. This is due to the increased viscosity of the blood and reduced deformability of red cells in patients with sickle cell anemia.

Bullet Summary:
Sickle cell trait is associated with episodes of painless hematuria.