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Sickle cell anemia (SCA) is found primarily in children of African, Arab, or Mediterranean descent. It is caused by a single amino acid substitution in the sixth position of the β-globulin chain of hemoglobin A (HbA). Children homozygous for this genetic abnormality have classic hemoglobin SS (HbSS) disease, whereas heterozygotes for HbS with a second β-globulin chain that is normal are considered to have sickle cell trait. Other patients may be heterozygous for HbS coupled with a heterozygous abnormality causing HbC or β-thalassemia. In general, patients with HbSC and the 90% of S/β-thalassemia patients with some normal β chains have fewer infectious and ischemic complications than patients with HbSS.

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The abnormal chain found in patients with SCA creates a hydrophobic region of the hemoglobin tetramer when it is deoxygenated.1 In this state, noncovalent polymerization of the hemoglobin molecules creates chains that distort the shape of the membrane, causing the characteristic sickle appearance. The altered red blood cell shape and its associated decreased deformability cause sickle cells to impede blood flow. This is responsible for most of the clinical manifestations of SCA. Interruption of blood flow created by the abnormal cells leads to poor tissue perfusion, acidosis, and hypoxia, which cause further sickling. The need to reverse these conditions is central to the management of SCA-related complications.

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Because fetal hemoglobin (HbF) is unaffected by these genetic mutations, symptoms of SCA don’t appear until HbF is replaced by the abnormal HbA. HbF predominates until 4 months of age, after which it rapidly declines, reaching baseline low levels just before 1 year of age. One of the first organs affected by the emerging sickle cells is the spleen. Recurrent splenic infarcts lead to a gradual decline in splenic function between 4 and 12 months of age, resulting in susceptibility to serious infections with encapsulated bacteria.

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In the U.S., all neonates are screened for SCA using highly sensitive and specific tests, so the diagnosis is rarely made in the ED. The clinical manifestations and potential complications of SCA, however, include symptoms that overlap considerably with diseases not related to SCA. Therefore, the diagnostic portion of this chapter is organized in a symptom-based fashion, and the treatment portion is grouped by disease physiology.

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Vaso-occlusive crises causing severe extremity pain are the most common manifestation of SCA, accounting for 79% to 91% of ED visits.2 Common triggers include stress, cold, dehydration, altitude, hypoxia, or illness. Pain preferentially affects the long bones and lower back. Individual patients tend to manifest their pain crises in characteristic locations, but the frequency of vaso-occlusive pain crisis is variable, even among SS homozygotes. Five percent of children with SCA account for 33% of total episodes, averaging between 3 and 10 pain crises per year.3 Children display variable degrees of tenderness over affected sites and may have slight temperature elevations without true fever. Because anemia can precipitate a crisis, patients should be assessed ...

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