[Systemic juvenile idiopathic arthritis. Pediatric-onset Still's disease]

Area of Science:

• Rheumatology
• Pediatric Rheumatology
• Immunology

Background:

• Systemic juvenile idiopathic arthritis (SJIA), or pediatric-onset Still's disease, typically begins before age 16.
• It shares characteristics with adult-onset Still's disease, presenting as a chronic autoinflammatory condition with potential joint and systemic complications.
• The rarity and evolving treatment guidelines necessitate early consultation with specialists.

Purpose of the Study:

• To highlight the importance of expert diagnosis in managing SJIA.
• To emphasize the need for differentiating SJIA subtypes based on distinct pathophysiologies and treatment responses.
• To address the increasing incidence of a specific SJIA phenotype associated with macrophage activation syndrome and high IL-18 levels.

Main Methods:

• Literature review on SJIA and adult-onset Still's disease.
• Analysis of clinical presentations and diagnostic complexities.
• Review of current and emerging treatment strategies, including biologics.

Main Results:

• SJIA is a complex autoinflammatory disease with potential for chronic articular and extra-articular manifestations.
• A specific SJIA subtype is increasingly observed, characterized by macrophage activation syndrome, elevated Interleukin-18 (IL-18), and poor response to anti-IL-1 or anti-IL-6 therapies.
• Accurate diagnosis and classification are critical for guiding appropriate patient care.

Conclusions:

• Early expert evaluation is essential for accurate diagnosis and management of SJIA.
• Recognizing distinct SJIA phenotypes, particularly the IL-18 driven form, is vital for optimizing therapeutic outcomes.
• Further research into the distinct physiological pathways and tailored treatments for SJIA subtypes is warranted.