This study looks at whether using macrolide antibiotics is helpful and safe in treating acute chest syndrome, a serious complication in people with sickle cell disease. It reviews past cases from three hospitals where patients were treated in intensive care. The goal is to understand if macrolides make a difference, what germs are involved, how useful lab tests are, and how well patients tolerate these antibiotics.

Inclusion Criteria:

• Adult patient (≥18 years old).
• Diagnosis of acute chest syndrome (ACS).
• Hospitalized in an intensive care unit (ICU).
• Microbiological sampling performed (e.g., multiplex PCR, sputum culture [ECBC], and/or Legionella urinary antigen test).
• Received empiric antibiotic therapy including a macrolide.

Exclusion Criteria:

• Minor patient (<18 years old).
• Acute chest syndrome not requiring ICU admission.
• Acute chest syndrome without any attempt at microbiological documentation.

The study population consists of adult patients (aged 18 and older) with sickle cell disease who were diagnosed with acute chest syndrome (ACS) and required hospitalization in an intensive care unit (ICU). All selected patients must have received an empiric antibiotic treatment including a macrolide and undergone microbiological sampling (such as PCR multiplex, sputum culture, or urinary antigen testing for Legionella). Participants will be identified retrospectively from medical records across the three participating hospital centers over the study period.