In contrast, the older sibling with IRAK-4 deficiency demonstrated raised levels of CRP (192 mg/l; normal < 5 mg/l) and IL-6 (1983 pg/ml; normal < 7 pg/ml), potentially indicating a prolonged infection, a disease course which has also been reported in other IRAK-4-deficient patients with severe IPD [31]. Here, CRP is linked to infection.