OBJECTIVE: To describe clinical characteristics and the homogeneity of dise
ase expression between involved members in multicase Spanish rheumatoid art
hritis (RA) families.
PATIENTS AND METHODS: 73 families with two or more siblings with RA were fo
und, with a total of 149 patients distributed in 79 pairs (70 sib pairs and
3 sib trios). Demographic, clinical and radiological characteristics were
recorded in a standard questionnaire.
RESULTS: Clinical characteristics were similar to those of sporadic RA with
a high frequency of women (78%), positive rheumatoid factor (RF) (86%), er
osions (89%) and a 25% of the patients having extraarticular disease. The m
ost important variable in disease severity was disease duration. The concor
dance between family members of the same age and calendar year of disease o
nset, and the pattern of disease expression, was not higher than expected,
showing that the disease is heterogenic.
CONCLUSION: Environmental factors seem to be more important in RA susceptib
ility, Clinical characteristics of familiar RA in Spain do not seem to be d
ifferent from sporadic RA, although differences were found in disease expre
ssion within families that may be due to variation of genetic or environmen
tal factors, responsible for the susceptibility and disease duration.