Familial aggregation in giant cell arteritis and polymyalgia rheumatica: a comprehensive literature review including 4 new families.

Objective: To review personal and published observations of giant cell (temporal) arteritis (GCA) or polymyal-gia rheumatica (PMR) with familial or conjugal aggregation and emphasise on epidemiological, clinical and genetic features of such cases.

Methods: We pooled data obtained from all cases of GCA or PMR with familial aggregation recruited in the department since 1976 and those from reports of familial or conjugal GCA or PMR published in the French-English literature since 1970.

Results: During the study period, we diagnosed 460 patients (128 with isolated PMR, 227 with isolated GCA, 105 with PMR/CGA). No conjugal couples were observed in the whole series. No familial cases were identified among PMR patients, whereas the prevalence of familial GCA was 1 in 83 (1 in 250 to 500 expected by chance), as we identified 4 patients (brother-brother, sister with history of affected sister, and daughter with priory affected mother). An additional pair of sisters with TA, recruited several months after diagnosis, is also presented. Pooling data from 85 patients (74 with GCA) including our patients, representing 32 families and 8 conjugal pairs, enabled us to draw the following observations: 1) partial or full agreement in the clinical picture (GCA, PMR, or GCA/PMR) was observed in 96% of the siblings pairs, suggesting a common pathogenic mechanism; 2) five kindred were described in whom at least three members were affected; 3) the lag between manifested diseases in familial or conjugal pairs averaged 5.7 years, with synchronous or close disease occurrence in only 26% of the pairs; 4) 18 of 32 assessed patients (56%) carried the DR4 antigen.

Conclusion: Our survey on familial aggregation of GCA and PMR accumulated data pointing to a genetic predisposition. However, environmental contagious factors could have trigger synchronous disease onset in up to one-fourth of the cases.