Determing an “autoimmune” phenotype in systemic JIA

Background

Data from research, clinics and response to treatment point out to an autoinflammatory pathogenesis in Systemic onset Juvenile Idiopathic Arthritis (SoJIA). However a subgroup of patients present with c hronic a ctive course of disease, destructive p olyarthritis and production of a utoantibodies (CAPA-subtype) not responsive to anti IL-1 treatment.

Aim

Determine phenotypic characteristics of the CAPA-subtype of SoJIA.

Methods

Retrospective analysis in a cohort of 35 SoJIA patients well characterized according clinical course and ANA, Rheumatic factor and ANCA.

Results

Autoantibodies have been found in 25,7% of the patients, with ANA being the most frequent auto-AK (table 1). There was a significant difference according the age of onset. Moreover females and carditis have been observed more frequently in the AK-pos. group.

SoJIA-Patients	35
Observation (month)	mean 69 (range 1-262)
	n	%	n	%
Autoantibodies	pos		neg
	9	25,7	26	74,3
ANA	6	17,1
RF	2	5,7
ANCA	3	8,6
	percentage for each group
male	3	33,3	11	42,3
female	6	66,6	15	57,7
onset age (years)	6,03		3,54
relapses	4		3,6
joints at onset	2,1		3,1
joints when AK pos	7
MAS	1		1
Carditis	6	66,7	13	50
SAA	2 of 4		8 of 12
Amyloidosis	1		1

Conclusion

There is evidence for an autoimmune course of disease in SoJIA in a subset of patients with chronic polyarthritis but without relapses of autoinflammation. These patients probably will need a switch in treatment to prevent further joint destruction.