Familial rheumatoid arthritis in patients referred to rheumatology clinics of Tabriz, Iran.
BACKGROUND
The familial clustering of rheumatoid arthritis (RA) in first and second degree relatives of patients supports the role of genetic factors. The proportion of heredity in its development is roughly 60%; however, most individuals closely related to someone with RA do not get the disease. Considering the lack of sufficient data on the familial aggregation of RA in Iran, we designed this study for clarifying the familial prevalence of RA.


OBJECTIVE
To determine the prevalence of RA among relatives of patients with RA and to evaluate the mean disease onset age in relatives.


METHODS
In a longitudinal study from July 2008 to July 2010, we followed 210 unrelated patients with RA and their first and second degree relatives (FDR+ and SDR+), by interviewing and physical examination of those with symptoms, to ascertain prevalence. Familial RA was defined by presence of at least two siblings fulfilling the 1987 ACR criteria for RA.


RESULTS
We demonstrated that 17.6% of patients have at least one affected relative. The prevalence of RA in the family of studied patients was 0.83% (42 people). Thirty-two in FDR+ and 10 people in SDR+ (2.53% and 0.26% of all family), also 1.12% in female relatives and 0.39% in male relatives had RA. The odds ratio for FDR/SDR was 2.52. The mean age at disease onset in relatives was 42.30 ± 1.51 years in FDR+ and 34.40 ± 2.10 years in the SDR+ group (0.03).


CONCLUSIONS
The risk of RA is greatest in FDR+ and is likely to be due to a combination of inherited and environmental factors.
Tabriz University of Medical Sciences, Tabriz University of Medical Sciences, Tabriz, Iran.
Mehrzad
M
Hajalilou
Hamid
H
Noshad
Ali R
AR
Khabbazi
Susan
S
Kolahi
Maryam H
MH
Azari
Mohsen
M
Abbasneghad
D000328:Adult; D017668:Age of Onset; D001172:Arthritis, Rheumatoid / Q000175:diagnosis / Q000453:epidemiology* / Q000235:genetics*; D016009:Chi-Square Distribution; D005260:Female; D020022:Genetic Predisposition to Disease; D040941:Heredity; D006801:Humans; D007492:Iran / Q000453:epidemiology; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D010044:Outpatient Clinics, Hospital / Q000706:statistics & numerical data*; D010375:Pedigree; D015995:Prevalence; D012017:Referral and Consultation / Q000706:statistics & numerical data*; D012219:Rheumatology / Q000706:statistics & numerical data*; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors