Reassessing the prevalence of monophasic, polyphasic and persistent disease courses in still’s disease

Objective: To classify Still’s disease (known as “systemic JIA”) course into monophasic, polyphasic and chronic-persistent disease, using data collected before and after the introduction of biologic IL-1/6 inhibitors, and identify predictors for a non-monophasic disease. Methods: A multi-center, retrospective chart review from 3 hospitals in Israel and 2 in the US, involving patients diagnosed with Still’s disease between 1998–2021, with a minimum follow-up of 1 year. Results: Eighty-two patients met the inclusion criteria, with a median follow up time of 2.8 years (1.1–17). Fifty-two (63.4%) were females; mean age at diagnosis was 6.4 ± 4.4 years. Fifty-nine (72%) were diagnosed in 2012 or later, when IL-1 and IL-6 inhibitors became widely used. The rates of monophasic, polyphasic and persistent disease were 34.1%, 46.3% and 19.5%, respectively, with a higher-than-expected rate of polyphasic disease. The proportion of a non-monophasic (polyphasic or persistent) disease decreased from 78.2% in cases diagnosed before 2012 to 61% in cases diagnosed after 2012 albeit not statistically significant (p = 0.22). In a multivariate logistic regression model, an active disease 3 months from diagnosis was an independent risk factor for a non-monophasic disease course (OR 4.16 [1.33–15.2], p = 0.02). Conclusions: Drug-free remissions in chronic, non-monophasic Still’s disease may be more common than previously demonstrated. In the age of IL-1 and IL-6 inhibitors, a monophasic disease course may be more prevalent. This finding provides further evidence that cytokine blockers may potentially alter the natural history of this disease, and that early aggressive treatment may be warranted.