Acute chest syndrome

Overview

Acute chest syndrome (ACS) is a serious and potentially life-threatening complication of sickle cell disease (SCD). It is defined by the presence of new pulmonary infiltrates on chest imaging accompanied by symptoms such as chest pain, fever, cough, and shortness of breath. ACS is one of the leading causes of hospitalization and death in patients with sickle cell disease, affecting both children and adults. It requires prompt diagnosis and aggressive treatment to reduce morbidity and prevent respiratory failure.

Causes

Acute chest syndrome results from a variety of factors that cause inflammation or obstruction in the lungs of individuals with sickle cell disease. Common causes include:

• Infection: Viral, bacterial, or atypical pathogens (e.g., Mycoplasma pneumoniae)

• Fat embolism: From bone marrow necrosis during vaso-occlusive crisis

• Pulmonary infarction: Due to sickled red blood cells blocking pulmonary vessels

• Atelectasis: Collapsed lung segments due to hypoventilation or pain

• Asthma or reactive airway disease: May trigger or exacerbate ACS

Symptoms

Symptoms of acute chest syndrome often overlap with pneumonia or pulmonary embolism and can vary in severity. Common signs and symptoms include:

• Fever (≥38.5°C or 101.3°F)

• Chest pain: Often pleuritic (worsens with breathing)

• Cough: Can be dry or productive

• Shortness of breath (dyspnea)

• Hypoxia: Low oxygen levels

• Tachypnea: Rapid breathing

• Wheezing or crackles on lung auscultation

• Abdominal pain or limb pain: Especially in children

ACS can develop during or shortly after a vaso-occlusive pain crisis, often within 24–72 hours of hospital admission.

Diagnosis

Prompt diagnosis is essential and relies on clinical assessment supported by imaging and laboratory findings. Key diagnostic steps include:

• Chest X-ray: Reveals new pulmonary infiltrates in one or more lobes

• Pulse oximetry: To assess oxygen saturation

• Blood tests: Including complete blood count (CBC), reticulocyte count, and blood cultures if infection is suspected

• Arterial blood gas (ABG): In severe cases to evaluate gas exchange

• Respiratory pathogen testing: Such as viral panels or sputum cultures

It is critical to distinguish ACS from pneumonia, pulmonary embolism, or other causes of chest pain in sickle cell patients.

Treatment

Management of acute chest syndrome is multifaceted and usually requires hospitalization. Treatment strategies include:

• Oxygen therapy: To correct hypoxia

• Incentive spirometry: To prevent atelectasis and promote lung expansion

• Pain control: Using opioids or other analgesics (avoid oversedation)

• Hydration: Intravenous fluids to reduce sickling (avoid overhydration)

• Antibiotics: Broad-spectrum antibiotics initially, tailored based on culture results

• Bronchodilators: If wheezing or asthma is present

• Blood transfusion: Simple or exchange transfusion in moderate to severe cases to reduce HbS concentration

Severe cases may require admission to the intensive care unit (ICU) and mechanical ventilation.

Prognosis

With timely and appropriate treatment, most patients recover from acute chest syndrome. However, it remains a major cause of morbidity and mortality in sickle cell disease. Recurrent episodes can lead to chronic lung damage and pulmonary hypertension. Long-term strategies to reduce recurrence include:

• Hydroxyurea therapy: To reduce frequency of sickling crises and ACS episodes

• Chronic transfusion therapy: In patients with frequent or severe ACS

• Preventive care: Including vaccinations and regular follow-up with a hematologist

Early recognition and aggressive treatment are key to improving outcomes and reducing the risk of complications or death.