Background/Purpose: Systemic-onset juvenile idiopathic arthritis (sJIA) is a pediatric autoinflammatory condition, known for significant variability between patients in its severity and long-term outcomes. The classification of disease course into monophasic, polyphasic (intermittent) and persistent disease has been commonly used, with polyphasic disease usually recognized in a small portion of patients^1,2 . However, this proportion was established according to data mostly collected before the biologic IL-1 and IL-6 inhibitors were available. It has been recently suggested ^3,4 that these medications, now the mainstay of treatment in sJIA, can potentially alter the long-term course of the disease, especially with earlier use.

Methods: A multi-center, retrospective chart review was conducted from 3 hospitals in Israel and 2 in the US, involving patients diagnosed with sJIA between 1998-2019, with a minimum follow-up of 1 year. Disease course classification was done according to previously released definitions.¹ Remission was defined as inactive disease (no active signs or symptoms and no elevation of inflammatory markers) while not receiving any medications for a period of at least 3 months. Polyphasic disease was defined as at least one disease relapse after a period of drug-free remission. Persistent disease was defined as at least 2 years of disease (either active or in remission on immunosuppressive medication) with no drug-free remissions. Monophasic disease was defined as a single episode lasting less than 2 years.

Results: : 85 patients met the inclusion criteria (mean follow up 3.6 years, SD ± 2.8). 54 of the patients (63.5%) were female; median age at diagnosis was 5.8 years (IQR = 5.9). 67 (78.9%) were diagnosed in 2012 or later, when IL-1 and IL-6 inhibitors became widely used. 56 (65.9%) were treated with a biologic drug during their disease course. The rates of monophasic, polyphasic and persistent disease were 43.5%, 43.5% and 12.9%, respectively, with a higher-than-expected rate of polyphasic disease and a lower rate of persistent disease than previously published. ^1,2,5

Conclusion: In the age of IL-1 and IL-6 inhibitors, polyphasic sJIA disease course may be more common than previously described, suggesting that cytokine blockers may potentially alter the natural history of this disease.

¹ Singh-Grewal et al, Arthritis Rheum. 2006² Barut et al, Int J Rheum Dis. 2019
³ Henderson LA et al, JCI Insight. 2020 ⁴Kessel C et al. (2020) Arthritis Rheumatol
⁵ Lomater et al, J Rheumatol. 2000

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/proportion-of-patients-with-a-polyphasic-disease-course-in-systemic-onset-juvenile-idiopathic-arthritis-may-be-higher-in-the-age-of-cytokine-inhibitors/