Should vasculitis be relabelled as an infection?
Len Calabrese presented the infection hypothesis behind vasculitis. He described the intriguing link between Herpes virus and stroke, and stated that all the primary CNS vasculitis cases at the Cleveland Clinic are having multiple infection testing performed on tissue (SP0131).
Several viruses are known to be associated with vasculitis (e.g. Hepatitis B and C to name a couple). There are 1031 different viruses, many of which have not yet been sequenced/identified.
Viral infections can be self-limited (e.g. URIs, rhinovirus), chronic persistent and replicative (e.g. HIV, Hep B and C), or chronic infection with latency and reactivation (e.g. Herpes viruses). Viruses that are cleared (e.g. Hep C with cryoglobulinemic vasculitis) can result in vasculitis that persists for a long time (one could think of inciting and perpetuating disease, and perhaps other factors become important). We also know that GCA (temporal arteritis) can cluster seasonally and even in certain years, which makes one wonder about a pathogen that could be inducing vasculitis.
A rose by any other name may not be a flower with thorns
Raashid Luqmani spoke about the different pathogenicities of ANCAs (SP0132). For instance, there is worse prognosis if a patient has proven SLE and is ANCA-positive. Remember the CCP/ACPA story (different serotypes and different citrullination may affect manifestations of RA)? It looks like ANCA may also be like that. Of course, MPO and PR3 are different and have different specificities for GPA (formerly known as Wegener’s granulomatosis). Other points of interest were that galactosylation or sialyation of ANCA antibodies can alter time to relapse in GPA, and regulatory cells and neutrophil cell nets can affect how ANCAs behave.
So the take home messages…
The cause of vasculitis in most patients will not be known, but in some circumstances should be looked for – i.e. find treatable causes.
All ANCAs are not created equally.
Dr. Janet Pope is Professor of Medicine at Western University and Division Head of Rheumatology. Dr. Pope's research interests include epidemiologic studies in scleroderma, classification criteria in systemic sclerosis, systemic lupus erythematosus and rheumatoid arthritis.View Full Bio