Patients presenting with MAS were significantly (p = 0.026) more likely to receive bDMARD at diagnosis (n = 15/27, 56%; anti-IL-1 n = 14, anti-IL-6 n = 1) compared to those that developed MAS later in their disease course (n = 1/8, 1%; anti-IL-1 n = 1, anti-IL-6 n = 0). Here, IL1B is linked to macrophage activation syndrome.