The diagnostic criteria for “double peaks of IL-6” included: (1) serum IL-6 level in the first peak declined steadily due to relief of CRS; (2) IL-6 in the second peak increased abruptly to more than 1000 pg/ml; (3) the fluctuation of IL-6 level induced by pharmacologic management such as corticosteroid and/or tocilizumab was excluded; (4) ferritin increase was less than 50%. The gene discussed is IL6; the disease is congenital rubella syndrome.