Rapidly progressive acute chest syndrome in individuals with sickle cell anemia: a distinct acute chest syndrome phenotype.

Current definitions of acute chest syndrome (ACS) in sickle cell anemia (SCA) do not account for rapid progression of respiratory compromise. In this two-center retrospective cohort study, we tested the hypothesis that in children and adults with ACS and respiratory failure (≤24 hours after onset of respiratory symptoms) have a distinct ACS phenotype associated with multiorgan failure when compared to those with ACS that have a more subacute and protracted course. We identified 173 individuals (97 children <20 years and 76 adults ≥20 years) with SCA and at least one episode of ACS. Only one ACS episode was considered per individual. Rapidly progressive ACS occurred in 21% (n = 16) of adults, but only 2.1% (n = 2) of children. Compared to adults without rapidly progressive ACS, adults with rapidly progressive ACS more frequently developed acute kidney injury (68.8% vs. 3.3%, P < 0.001), hepatic dysfunction (75.0% vs. 15.0%, P < 0.001), altered mental status (43.8% vs. 11.7%, P < 0.001), multiorgan failure (93.8% vs. 10%, P < 0.001), and death (6.3% vs. 0%, P = 0.05). Clinical and laboratory covariates that were evaluable on the first day of respiratory symptoms were evaluated to identify predictors of rapidly progressive ACS. On multivariable analysis, decline in platelet count at presentation was the only predictor of rapidly progressive ACS [odds ratio 4.82 (95% CI 1.20-19.39), P = 0.027]. In conclusion, rapidly progressive ACS is a distinct phenotype that occurs more frequently in adults, is preceded by thrombocytopenia, and is associated with multiorgan failure. Am. J. Hematol. 91:1185-1190, 2016.