Positivity according to the ILAR criteria correlated with the systemic score (r = 0.763, p <  0.0001) and C-reactive protein levels (r = 0.183, p = 0.0356) and was associated with a relapse (odds ratio: 1.589, 95% CI: 1.043–2.421), macrophage activation syndrome (MAS; odds ratio: 1.993, 95% CI: 1.218–3.263) and care in the intensive care unit (ICU; odds ratio: 2.087, 95% CI: 1.086–4.011). The gene discussed is CRP; the disease is macrophage activation syndrome.