Purpose Urticarial vasculitis (UV) is a rare type of vasculitis in children frequently, idiopathic, however, can be associated childhood onset SLE. The aim of the study is to describe the frequency of UV in cSLE and to compare the epidemiological, clinical and laboratory characteristics of cSLE stratified by the presence of UV in a cohort of patients of Arab ethnicity from Oman.

Methods We conducted a retrospective multicenter study among pediatric rheumatology centers in Oman over a 10year period.

Results A total of 148 cSLE patients, n=44 males (30%) and n=104 (70%) females, with male to female ratio of 1:2.4 were included in the study. The overall mean age at diagnosis was 7.6±3.5 years and median disease duration was 9.5 years. A total of 36% (n=53) of children with SLE were diagnosed with UV. cSLE with UV were more likely to be males (57% vs 15%; p<0.001), with a family history of SLE (53% vs 36%; p=0.044), diagnosed at a younger age (5.9 vs 8.5 years; p<0.001) and originating from the Al-Sharqiya region of Oman (62% vs 29%; p<0.001). Compared to cSLE without UV, the clinical features of UV cohort was more frequently associated with conjunctivitis (32% vs 5.3%; p<0.001). However, the UV cohort was less likely to be associated malar rash (5.7% vs 31%; p<0.001), CNS involvement (20% vs 7.6% p =0.045) and hematological manifestations such as leukopenia (9.4% vs 24%; p=0.028), lymphopenia (28% vs 51%; p=0.009) and thrombocytopenia (5.7% vs 18%; p=0.045). When compared to cSLE without UV, the laboratory features of UV cohort was more likely to be associated with low C3 complement count (94% vs 66%; p<0.001) and cytoplasmic antibody ANCA (11% vs 0%; p=0.022). However, the UV cohort was less likely to be associated with ANA (65% vs 83%; p=0.016), DsDNA (56% vs 72%; p=0.042) and perinuclear anti-neutrophil cytoplasmic antibodies (33% vs 55%; p=0.047).

Conclusion We describe relatively high occurrence of UV (36%) in a cohort of cSLE of Arab ethnicity with unique clinical and laboratory features. Further studies are needed to evaluate the relationship of UV with SLE and to study the role of genetic, ethnic and environmental factors in disease expression.