Ethnic heterogeneity of juvenile arthritis in the Republic of Sakha (Yakutia) related to a high human leukocyte antigen B27 frequency

Table 3 Clinical, demographic, and laboratory characteristics of children with juvenile idiopathic arthritis in the Republic of Sakha (Yakutia), n (%)

Parameters	n = 225
Gender: Boys [n (%)]/girls [n (%)]	107 (47.6%, 95%CI: 41.1-54.1)/118 (52.4%, 95%CI: 45.9-58.9])
Age at JIA onset, medians (25%, 75%)	9 (5, 12)
Family history of immune-inflammatory diseases	60 (26.7%, 95%CI: 21.3-32.8)
Arthritis in the close relatives	46 (20.4%, 95%CI: 15.7-26.2)
JIA categories, International League of Antirheumatic Associations
Systemic arthritis	8 (3.5%, 95%CI: 1.8-6.9)
Oligoarthritis	76 (33.8%, 95%CI: 27.9-40.2)
Polyarthritis, RF (-)	33 (14.7%, 95%CI: 10.6-19.9)
Polyarthritis, RF (+)	2 (0.9%, 95%CI: 0.2-3.2)
Enthesitis-associated arthritis	99 (44.0%, 95%CI: 37.7-50.5)
Psoriatic arthritis	7 (3.1%, 95%CI: 1.5-6.3)
Active joints, medians (25%, 75%)	4 (2, 10)
Sacroiliitis	43 (19.1%, 95%CI: 14.5-24.8)
Enthesites	34 (15.1%, 95%CI: 11.0-20.4)
Uveitis	23 (10.2%, 95%CI: 6.9-14.9)
Psoriasis	7 (3.1%, 95%CI: 1.5-6.3)
Antinuclear antibodies-positivity	30/45 (66.7%, 95%CI: 52.1-78.6)
Human leukocyte antigen-B27 positivity	87/220 (39.6%, 95%CI: 33.3-46.1)
RF-positivity	1 (0.4%, 95%CI: 0.1-2.5)

JIA: Juvenile idiopathic arthritis; RF: Rheumatoid factor.