From the EM Model
8.0 Hematologic Disorders
8.5 Red Blood Cell Disorders

Sickle cell disease (SCD) is a hereditary hemoglobinopathy that is characterized by anemia and a wide array of pathology secondary to intermittent small blood vessel occlusion. It is estimated that 1 in 600 African Americans in the United States has the disease; in addition, SCD can be seen in people of Indian, Mediterranean, and Middle Eastern descent. Children with SCD presenting to the emergency department represent a unique challenge. Even though vaso-occlusive crisis (VOC) is the most common presentation, there is a much higher incidence of potentially life-threatening pulmonary, central nervous system, gastrointestinal, and infectious complications in children because of the unique anatomic and physiologic characteristics of children. This, along with the challenges in obtaining an accurate history and physical examination, makes it important that emergency physicians understand the complexities of SCD in children.

Pediatric Sickle Cell Anemia Acute Vaso-occlusive Crisis

VOC is the hallmark of SCD and is the most common emergency department presentation of the pediatric patient, representing over 90% of all visits.¹ VOC is due to ischemia or infarction of tissue that results from the sludging of sickled and nonsickled RBCs within the microvasculature and results in the mild to severe pain seen in this crisis.

Although a number of biologic (infection, dehydration, menstruation, physical exertion, hypoxia), environmental (change in ambient temperature), and emotional (anxiety, depression) precipitants for VOC exist, most VOC occurs spontaneously, and the cause is often not identified.

Critical Decision

What are the findings associated with clinically significant complications of sickle cell disease in children?

Preverbal children may present with fussiness, inconsolable crying, altered sleep patterns, or diminished feeding. Verbal children typically describe pain in almost any part of the body. It is most commonly seen in the chest, abdomen, low back, and extremities. In typical acute VOC, the pain in the spine, long bones, and chest is thought to occur from bone marrow ischemia as well as bone marrow hyperplasia (secondary to enhanced RBC production). The patient and/or caregiver may note similar patterns of pain in location and severity from crisis to crisis and may thus be able to describe whether the current episode is “typical.” The pattern can mimic other emergent conditions (acute abdomen, pulmonary embolus, renal colic), making diagnosis more challenging. The duration of a painful crisis varies but is typically four to six days. Some patients, however, can experience pain for weeks and could return to the emergency department for multiple visits during this time. Although most patients with SCD are able to manage their pain as outpatients, 10% to 20% have pain severe enough to require emergency department treatment and possible inpatient care.²

Anemia

Anemia can result from increased hemolysis due to the fragility of sickled RBCs. Hyperhemolytic crisis is characterized by increased destruction of RBCs and can be seen in VOC or with associated infection. Decreased hemoglobin, increased reticulocyte count, increased bilirubin, and increased lactic dehydrogenase are typical laboratory findings. Aplastic crisis occurs when RBC production is suppressed. There is variability in the decrease in hemoglobin, and the reticulocyte count is typically less than 2%. Infection is the most common etiology, with parvovirus B-19 as the most common agent. Aplastic crisis can also serve as the trigger for a VOC episode.³

Dactylitis

Dactylitis (or hand-foot syndrome) is the earliest clinical manifestation of SCD. It occurs most commonly in children between the ages of 6 months and 2 years. Dactylitis often presents with acute, symmetric, painful swelling of the dorsal part of the hands and feet and is caused by ischemia and infarction of the bone marrow. The edema is nonpitting and involves the soft tissue over the metacarpals and metatarsals and the proximal phalanges of the hand and feet. It occurs in these areas in this age group because hematopoiesis occurs in these peripheral areas. As children age, hematopoiesis shifts to more central locations such as the arms or legs. Patients can be febrile, and the physical examination will show erythema, warmth, and tenderness. Radiographs typically do not demonstrate bony abnormalities. Interestingly, patients who develop dactylitis before 12 months of age are 2.6 times as likely to develop severe SCD during their lives.⁴

Infection

SCD patients are particularly at risk for infection by organisms such as Pneumococcus, Staphylococcus species, Haemophilus influenzae, and Salmonella. Children can present with signs of pneumonia, urinary tract infection, or meningitis. Children with SCD have a several hundred-fold risk for sepsis. The risk for overwhelming sepsis is highest before age 3.⁵

Stroke

Children with SCD are at increased risk for stroke, with a 400-fold increase in cerebral infarction when compared to patients without the disease.⁶ Stroke incidence peaks between four and six years of age, and it is estimated that 10% of all SCD patients will suffer a stroke by age 20.⁷ Although a variety of neurologic deficits can be found (based on the area of insult), hemiplegia is the most common physical examination finding, followed by focal seizures. Additional findings include any focal neurologic deficit, headache, seizure, and change in mental status.

Splenic Sequestration

The abdomen is the second-most common site of pain in SCD after the musculoskeletal system. The spleen serves as a filter for abnormal RBCs and is one of the first organs to suffer from the effects of intravascular sickling. Children between 5 months and 2 years are the most vulnerable to acute splenic sequestration crisis, a condition in which the spleen acutely sequesters large numbers of RBCs. This results in obstruction of venous outflow from the spleen, leading to pooling of red cells and platelets within the spleen. Diminished flow leads to an acidotic environment, further sickling, increased blood viscosity, and further obstruction.