The “Ammann” rule describes patients at low risk of significant bacterial infection as from weighted factors including: bone marrow involvement, clinical signs of viral infection, serum C-reactive protein (CRP) level, leukocyte count, presence of a central venous catheter, high haemoglobin level, and diagnosis of pre-B-cell leukaemia (see Table 1 for details). The gene discussed is CRP; the disease is bacterial infectious disease.