A nurse is caring for an adolescent who has sickle-cell anemia. Which of the following manifestations indicates acute chest syndrome and should be immediately reported to the provider?

A. Sneezing is a mild symptom unrelated to acute chest syndrome. B. Substernal retractions indicate respiratory distress, a hallmark of acute chest syndrome, which is a life-threatening complication of sickle-cell disease caused by sickling in the pulmonary vasculature. This leads to hypoxia, chest pain, fever, and respiratory failure if untreated. C. Hematuria may occur with sickling in renal capillaries but is not an emergency. D. A low-grade fever is common in infection or inflammation but does not indicate acute chest syndrome by itself.