Background and aims To describe the familiality and concordance of manifestations among Filipino patients with systemic lupus erythematosus (SLE) and their affected first degree relatives (FDR).

Methods Filipino mulitplex SLE families with at least 2 first degree relatives (FDRs) diagnosed as SLE were identified from University of Santo Tomas (UST) Lupus Database. Demographic and disease characteristics were described, and types of relationships within families were analysed for concordance of presenting manifestations using McNemar and Fisher’s Exact tests, with significance at p<0.05.

Results The prevalence of familial SLE in the UST Lupus Database (n=2474) was 7.8%. There were 192 patients (173, 90% females) from 95 families (2 families with 3 FDRs), including 25 parent-offspring pairs (23 mother-daughter) and 70 sibling pairs (56 sister-sister). Average age at SLE diagnosis was 31+11.4 SD (range 5–68) years for all affected FDRs. Among parent-offspring pairs, parents’ age averaged 44.8+9.7 SD (range 29–68) years and their offsprings averaged 23.6+10.6 SD (range 5–35) years at SLE diagnosis, p<0.001. Average age at SLE diagnosis among sibling pairs was 28.6+11.4 SD (range 9–55) years, with a positive linear association of age at SLE diagnosis between siblings, p<0.001. Most common presenting manifestations were malar rash (47%), oral ulcers (45%), photosensitivity (40%), hematologic (39.9%) and arthritis (39%). Concordance among related FDRs was significant for oral ulcers and hematologic manifestations, p<0.05.

Conclusions This study underscores the role of genetics in age onset and clinical expression of lupus.