CTSA and systemic inflammatory response syndrome: Furthermore, azurophilic granule signature genes were elevated in sepsis but not in SIRS, among them the independently validated lysosomal genes CTSA, HEXA, GUSB, and RNASE2. This particular expression pattern is explained in the most straightforward manner by higher blood counts of both promyelocytes and myelocytes in sepsis than in SIRS, as indeed seen in an extension of the validation cohort (Figure 4A).