FAMILIAL AGGREGATION OF JUVENILE IDIOPATHIC ARTHRITIS

Pediatric Rheumatology Online Journal → June 2003 → Epidemiology, Classification, Immunology and Immunogenetics → Abstract #4

S. Prahalad,¹ E. O'Brien,² A. Fraser,² R. Kerber,^2,3 G. Mineau,^2,3 J. Bohnsack.¹

¹Pediatrics, U of Utah SOM, Salt Lake City, UT; ²Huntsman Cancer Institute, U of Utah, Salt Lake City, UT; ³Dept of Oncological Sciences, U of Utah, Salt Lake City, UT

Objectives: To determine if there is familial aggregation of juvenile idiopathic arthritis (JIA), by linking a clinical database and a computerized genealogical database.
Methods: Patients with JIA or possible JIA in a clinical database were linked with records in the Utah Population Database (UPDB), a computerized genealogy database of over 6 million records. For each linked case, 10 controls matched on sex and birth year were selected. Next all 1^st, 2^nd, 3^rd, 4^th and 5^th-degree relatives of both the cases and controls were identified. For all relative pairs (or a random sample of 100,000 if the number is 100,000) we tested the hypothesis that being a relative of a case is a risk factor compared to being a relative of a control.
Results: A total of 443 (63.6%) patients linked to the UPDB. Of these 384(86.7%) had definite or probable JIA. Four patients had iritis, 11 had onset after 16 years, and 44 had possible JIA. Of those with JIA, the subtypes n(%) were: Systemic 41(10.7), poly RF+ 23(6.0), poly RF ve 65(16.9), oligo 177(46.1), enthesitis related arthritis 58(15.1), psoriatic arthritis 5(1.3), and other 15(3.9). The cases had 1,563 1^st-degree relatives, and a total of 15,157 relatives. The controls had 15,773 1^st-degree and a total of 176,992 relatives. The recurrence risk of JIA was greater among the relatives of cases compared to relatives of controls. [8/15157 vs. 50/176992, RR(95%CI) = 1.87(0.9-3.88)]. This was due predominantly to the excess prevalence of JIA among 1^st-degree relatives of cases compared to 1^st-degree relatives of controls. [6/1563 vs. 2/15773, RR = 30.38(7.01-inf)]. The overall prevalence of JIA was 28/100,000.
Conclusions: These results suggest that JIA is more common among family members of patients with JIA. However the results are predominantly due to the large excess among the 1^st-degree relatives, which could possibly reflect referral bias. The overall prevalence of JIA in this study is lower than several estimates. This could be due to incomplete ascertainment.