The top 5 causes of index admissions were hemoglobin SS (Hb-SS) disease with crisis, unspecified (51.3%); Hb-SS disease with acute chest syndrome (4.3%); hemoglobin SC disease with crisis, unspecified (3.9%); sepsis, unspecified organism (3.3%); and sickle cell thalassemia, unspecified, with crisis (2.0%). This evidence concerns the gene GSTM1 and acute chest syndrome.