All patients with MAS (full-blown + possible MAS) receiving TCZ also had significantly lower serum ferritin levels (664 ng/ml vs 9235 ng/ml; p < 0.001) (Table 2 and Fig. 1a), serum TG levels (113 mg/dl vs 214 mg/dl; p < 0.05) (Table 2 and Fig. 1b), and serum CRP levels (0.03 mg/dl vs 7.6 mg/dl; p < 0.0001) than the TCZ-untreated patients (Table 2 and Fig. 1c). The gene discussed is CRP; the disease is macrophage activation syndrome.