Studies on the Epidemiology and Outcome of Primary Systemic Vasculitis

Sammanfattning: Primary Systemic Vasculitides [PSV: Wegener's granulomatosis (WG), microscopic polyangiitis (MPA), Churg-Strauss syndrome (CSS) and polyarteritis nodosa (PAN)] are rare systemic diseases of unknown etiology; if untreated, they are associated with high morbidity and mortality rates. Changes in the classification and diagnostic improvements during the last decades have increased reported prevalence and incidence rates of PSV. However, many uncertainties remain regarding the epidemiology of PSV. This thesis contains a comprehensive description of the epidemiology and outcome of PSV from a stable population in southern Sweden. (I) Using multiple retrieval sources, all prevalent cases with PSV within a defined population were identified to determine the point prevalence (p.p.) per January 1, 2003. Eighty-six patients fulfilled the study criteria for PSV, which equals a prevalence of 299 cases per million inhabitants (160 for WG, 94 for MPA, 14 for CSS and 31 for PAN). This is the highest prevalence figure ever reported for PSV. By capture-recapture analysis the case completeness was estimated to be 97%. (II) The extent of irreversible organ damage, on the date of p.p., was measured using the Vasculitis Damage Index (VDI), for all the 86 patients from Paper I. Organ damage was very common in our patients, the medium VDI score was 3 and only 9% had not been assigned any item of damage. The most common type of damage was cardiovascular, followed by renal, neuropsychiatric and ear-nose-throat (ENT). ENT damage was more prevalent in younger while renal damage was more common in older patients. (III) The annual incidence rate for the PSV was estimated during a10-year period in two healthcare districts in southern Sweden with a total population of 640 000. A total of 140 patients fulfilled the study criteria. The incidence rate for the whole PSV group was 21/million (9.8 for WG, 10.1 for MPA and 0.9 for CSS and PAN each). For all patients, absolute survival rates were 87.8% at 1 year, 71.6 % at 5 years and 55 % at 10 years. Survival was better for WG then MPA. High age and renal disease at onset were the strongest predictors for mortality. (IV) The possible influence of cigarette smoking on the development of permanent organ damage was studied using cases from Paper I. Data were analyzed from 77 patients for whom data on smoking habits were available. Patients smoking at onset tended to develop more renal and cardiovascular damage. However, none of those who smoked at the time of diagnosis subsequently developed ENT damage.