Background/Purpose: Since first described by McDuffie et al. in 1973, hypocomplementemic urticarial vasculitis (HUV) syndrome has been recognized as a specific autoimmune disorder involving at least 6 months of urticaria with hypocomplementemia in the presence of systemic manifestations, such as arthritis/arthralgia, glomerulonephritis, uveitis and recurrent abdominal pain. Skin biopsy is essential in the diagnosis of HUV and the presence of antibodies against complement protein 1q (anti-C1q) has been judged ‘a rule without exception’. The objective of this study was to describe the clinical characteristics and epidemiology of HUV in two geographically areas of Sweden during a 16-year period.

Methods:   In the health care districts surrounding the Skåne University Hospital in Lund [mean population years (2000-2015), 950 560] and the Linköping University Hospital in Östergötland [mean population years (2000-2015), 428 503] all patients diagnosed with HUV during the period 2000-2015 were included in the study if they (i) were residing within the study areas at the time of onset of HUV-related symptoms, (ii) had received a diagnosis of HUV during the study period. The diagnosis of HUV was confirmed by medical records review. Only patients meeting the suggested diagnostic criteria for HUV [1] and/or the 2012 Chapel Hill consensus definitions [2] were included.

Results: Sixteen patients (Skåne 7 + Östergötland 9) with a clear female predominance were identified during the study period. Clinical characteristics of the patients are given in Table 1. The pooled annual incidence rate per million inhabitants was estimated to 0.7 (95% CI 0.4-1.1), with a significant higher incidence in Östergötland compared to Skåne [0.5 (95% CI 0.1-0.8) and 1.3 (0.5-2.2), P=0.02]. The prevalence did not differ significantly between the regions, Table 2). Two patients died during the follow-up period. One patient underwent lung transplantation and two patients proceeded to end-stage renal disease.

Conclusion:   To our knowledge, this is the first epidemiological study of HUV. The high coverage of patients, which was enabled by the public and tax-funded Swedish healthcare system, constitutes a major strength of this study. The estimation of incidence and prevalence indicate that this condition is rare but not benign. Renal and lung manifestations were severe in some cases which highlights the need for careful screening and monitoring of this potentially serious condition. References:  1) Davis MD, Brewer JD. Immunol Allergy Clin North Am 2004;24:183-213 2) Jennette JC, et al. Arthritis Rheum 2013;65:1-11

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/hypocomplementemic-urticarial-vasculitis-huv-syndrome-in-two-geographically-defined-populations-of-sweden/