Background/Purpose: Differences in both presentation and outcome based on age of diagnosis have been described in patients with IgA vasculitis (IgAV) but data are limited due to cohort size and follow-up duration. The aim of this study was to describe the clinical characteristics and outcome of a large single-institution cohort of biopsy-proven IgAV.

Methods: Patients with biopsy-proven IgAV from 1997 to 2016 were retrospectively identified. Clinical characteristics, laboratory parameters and outcomes were abstracted from direct medical chart review. Proteinuria was classified as non-nephrotic (≥0.2 g/d, ≤3.5 g/d) or nephrotic (>3.5 g/d). Microscopic hematuria was defined as ≥5 RBCs/hpf or ≥2+ on dipstick. Disease activity at each follow-up visit was categorized as complete response (normalization of all baseline abnormalities due to IgAV), partial response, non-response (lack of improvement of any abnormalities due to IgAV) or relapse (development of clinical signs of IgAV after a symptom-free period of at least one month).  Prevalence of disease activity was estimated using multi-state models, which account for competing risks.

 Results: A total of 243 IgAV patients were identified (97% Caucasian, 58% male). 174 patients were adults (>21 years) and 69 were <21 years. ACR criteria were met in 98% of adults and 100% of patients <21 years. Compared to patients <21 years, adults at baseline had more frequent ulcerative skin lesions (11% vs. 1%; p=0.02) and nephrotic-range proteinuria (22% vs. 3%; p=0.007) but less commonly had abdominal pain (34% vs. 61%; p<0.001), ischemic gastrointestinal involvement (10% vs. 20%; p=0.04) and arthralgias (38% vs. 61%; p<0.001). Frequency of baseline microscopic hematuria was similar between groups (47%). 8 adults, but no patients <21 years, presented with end-stage renal disease. Oral (80%) and topical (23%) corticosteroids were the most common initial treatments used. Conventional immunosuppressive drugs were used at diagnosis in only 12% of patients.

Dialysis was required in 13 patients (8 adults) and renal transplant was performed in 4 cases (1 adult). Of 137 patients with hematuria during the study, 72% had complete resolution of hematuria by 1 year after onset, compared to 50% of 179 patients with proteinuria. The prevalence of disease activity state at each follow-up time point is shown in figure 1.  During 389 person-years of follow-up, 29 deaths were observed. Five year survival rates (95% CI) for patients aged <21, 21-50, and 51+ years were 100%, 94% (87, 100) and 40% (26, 63), respectively (p<0.001). Standardized mortality ratio for patients aged 21-50 years at diagnosis was 5.62 (0.68, 20.3) and 7.60 (5.0, 11.1) for those 51 or older. 

Conclusion: IgAV in adults is associated with more severe skin and kidney involvement, poorer renal outcome and increased mortality compared to patients diagnosed before 21 years of age.