What is the prevalence of sickle cell crises, specifically Painful Vaso-Occlusive Crisis (PVOC) versus Acute Chest Syndrome (ACS) versus splenic sequestration?

From the Guidelines

Sickle cell disease is characterized by various acute complications, with painful vaso-occlusive crises (PVOC) being the most common, affecting approximately 50-60% of patients with SCD annually, followed by acute chest syndrome (ACS) in about 10-20% of patients, and splenic sequestration in approximately 7-30% of children with SCD under 5 years of age. PVOC results from sickled red blood cells blocking small blood vessels, causing tissue ischemia and severe pain 1. ACS is a leading cause of hospitalization and mortality in SCD patients, characterized by fever, chest pain, respiratory symptoms, and new pulmonary infiltrates on chest imaging 1. Splenic sequestration is less common, affecting primarily children under 5 years of age, as the spleen typically becomes fibrotic and nonfunctional in older patients due to repeated infarctions, and involves rapid enlargement of the spleen due to trapped red blood cells, leading to acute anemia and potentially hypovolemic shock 1.

Key Complications and Their Prevalence

• PVOC: 50-60% of patients with SCD annually
• ACS: 10-20% of patients with SCD annually
• Splenic sequestration: 7-30% of children with SCD under 5 years of age

Management of these complications includes:

• Prompt pain control with opioids for PVOC
• Antibiotics and oxygen therapy for ACS
• Immediate fluid resuscitation and possible transfusion for splenic sequestration Hydroxyurea therapy at doses of 15-35 mg/kg/day can reduce the frequency of all these complications by increasing fetal hemoglobin production, which inhibits sickling of red blood cells 1.

Management Strategies

• Hydroxyurea therapy to reduce complication frequency
• Transfusion support for severe cases, such as ACS, with the choice between simple and exchange transfusion depending on the severity of the case and the patient's condition 1.

From the Research

Prevalence of Sickle Cell Crises

• The prevalence of sickle cell crises, including PVOC (Painful Vaso-occlusive Crisis), ACS (Acute Chest Syndrome), and splenic sequestration, varies among patients with sickle cell disease 2.
• PVOC is the most common reason for presenting to the Emergency Department and hospitalization in patients with sickle cell disease, with a complex pathophysiology involving secondary events 3.
• ACS is a serious complication of sickle cell disease, but its prevalence is not as well-defined as PVOC 2.
• Splenic sequestration is a potentially life-threatening event that is characteristic of sickle cell disease, with a higher risk of recurrence in patients who experience their first episode before 2 years of age 4.

Comparison of PVOC, ACS, and Splenic Sequestration

• PVOC and ACS are both acute complications of sickle cell disease, but they have different pathophysiologies and clinical presentations 3, 2.
• Splenic sequestration is a distinct entity that can occur in patients with sickle cell disease, particularly in those with homozygous sickle cell disease (HbSS) or compound heterozygous disease (HbSbetaThal, HbSC, HbSD) 5, 4.
• The treatment of splenic sequestration often involves blood transfusions or splenectomy, whereas PVOC and ACS may be managed with pain control, oxygen therapy, and other supportive measures 4, 6, 2.

Risk Factors and Treatment

• Age is a significant risk factor for the recurrence of splenic sequestration, with a lower risk of recurrence when the first episode occurs after 2 years of age 4.
• The treatment of splenic sequestration may involve watchful waiting, blood transfusions, or splenectomy, depending on the severity of the episode and the patient's overall condition 4, 6.
• Red cell exchange may be considered in adults with HbSC disease and acute splenic sequestration crisis who do not respond to simple transfusion 6.