Background/Purpose: Cyroglobulinemic vasculitis (CV) and IgA vasculitis are forms of small-vessel vasculitis characterized by immune complex deposition. The purpose of this study was to a) describe the characteristics of an international internet-based cohort of patients with a self-reported diagnosis of CV or IgA vasculitis and b) determine the extent to which these diagnoses agreed with established definitions of disease or classification criteria.

Methods: Participants with self-reported diagnoses of CV or IgA vasculitis were included in a prospective, internet-based, longitudinal registry from November 2014 to May 2020. All information was self-reported including diagnosis, symptoms at onset, and diagnostic testing.

Results: CV: 117 participants reported a diagnosis of CV (79% female). The racial/ethnic distribution was: 86% Caucasian/White, 3% Asian, 3% Hispanic/Latino and 2% African American/Black. Mean age at diagnosis was 48.7 ± 2.6 years. 22% had a history of hepatitis C and 13% of hematologic malignancy. 96% reported positive serum cryoglobulins. Common clinical manifestations included: purpura (94%), peripheral nerve involvement (93%), joint involvement (91%), and kidney involvement (27%). The establishment of the diagnosis was by laboratory testing (84%), symptoms (60%), and biopsy (37%). 108 participants (92%) met the Chapel Hill Consensus Conference (CHCC) definition.

IgA vasculitis: 103 participants reported a diagnosis of IgA vasculitis (75% female). The racial/ethnic distribution was: 88% Caucasian/White, 5% Asian, 5% Hispanic/Latino, 2% American Indian/Alaska Native, and 1% African American/Black. Mean age at diagnosis was 42.7 ± 3.2 years, with 77 (75%) developing symptoms in adulthood (≥18 years); there were few differences in clinical manifestations based on age of presentation (Table 1). 52% reported onset after an upper respiratory infection. Common clinical manifestations included: purpura (99%), joint involvement (93%), gastrointestinal pain/bleeding (70%), and kidney involvement (66%). Patients reported their diagnosis was established by biopsy results (68%), symptoms (62%), and serum laboratory testing (52%). 96 participants (93%) met the 1990 American College of Rheumatology criteria while 70 (68%) met the CHCC definition.

Conclusion: Self-reported clinical manifestations of CV and IgA vasculitis are similar to cohorts utilizing the traditional center-based approach. In addition, most patients with these diseases met established criteria or definitions for their disease. The diagnosis of CV appears to be more commonly reliant on laboratory testing as opposed to IgA vasculitis in which the diagnosis is more heavily based on biopsy results. Patients with adult-onset IgA vasculitis were more likely to develop peripheral neuropathy and thrombocytopenia. Patient-derived data from online registries is a feasible option for the conduct of future clinical trials in these rare and understudied diseases.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/clinical-characteristics-of-an-internet-based-cohort-of-participants-with-a-self-reported-diagnosis-of-cryoglobulinemic-vasculitis-or-iga-vasculitis/