JRA affected sibpairs: extent of clinical phenotype concordance

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Arthritis Rheum. 2004 Jun;50(6):1928-34.

Juvenile rheumatoid arthritis affected sibpairs: extent of clinical

phenotype concordance.

Moroldo MB, Chaudhari M, Shear E, SD, Glass DN, Giannini EH.

Cincinnati Children's Hospital Medical Center, and University of

Cincinnati, Ohio 45229-3039, USA. marta.moroldo@...

OBJECTIVE: To investigate the clinical phenotypes and demographic

characteristics of 183 affected sibling pairs (ASPs) with juvenile

rheumatoid arthritis (JRA) and to determine whether there are

differences between the clinical phenotypes of the ASP cohort compared

with patients with sporadic disease and whether there is greater sharing

of specific clinical features within versus between sibpairs. METHODS:

Details of the JRA Affected Sibpair Registry operations have been

described previously. The frequencies of phenotypes in the 2 cohorts

were tabulated, summary statistics were determined, and comparisons were

made by chi-square test or t-test. Sibling risk, sibling risk ratios

(lambda(s)), and odds ratios were calculated to assess familial

aggregation of several different clinical manifestations. RESULTS: The

most common onset type among the 164 nontwin ASPs was pauciarticular

(65% overall). Fifty-three percent of the ASPs were concordant for

pauciarticular-onset JRA; 19% were concordant for a polyarticular

disease onset. Among subjects with polyarticular-onset disease,

significantly more joints were involved at onset in simplex patients

than in ASPs (P = 0.008). The difference in age at JRA onset within

sibpairs (sibling 1 versus sibling 2) was not significantly different.

ASPs developed disease at a mean real-time difference of 5.1 years

apart. Familial aggregation was found for tenosynovitis (lambda(s)

29.5), leukocytosis (lambda(s) 25), rheumatoid factor (lambda(s) 11.0),

anemia (lambda(s) 1.7), and antinuclear antibodies (lambda(s) 1.3).

CONCLUSION: This study confirms the findings of earlier studies showing

that a high proportion of ASPs overall show concordance of disease-onset

type, except for the subset of patients with systemic disease, and that

nontwin ASPs do not develop disease at the same point in real time. We

conclude that JRA and its clinical manifestations do not differ

substantially between ASPs and the simplex population. The exception is

the number of affected joints at JRA onset among patients with

polyarticular-onset disease. Familial aggregation of clinical features

among ASPs adds strong evidence for a genetic background in this

disease.

PMID: 15188369

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