It was concluded through analysis that the use of hormones (χ2 = 14.203, P = 0.000), neutropenia or agranulocytosis (χ2 = 17.938, P = 0.000), Hb < 90 g/L (χ2 = 9.947, P = 0.002), and CRP > 15 mg/L (χ2 = 10.493, P = 0.001) were independent influencing factors that may cause severe pneumonia (Table 3). The gene discussed is GSTM1; the disease is Absence of circulating granulocytes.