Small-vessel vasculitis with prominent IgG4 positive plasma cell infiltrates as potential part of the spectrum of IgG4-related disease: a case report.

IgG4-related disease (IgG4-RD) is a systemic entity characterised by multiorgan inflammatory lesions with abundant IgG4+ plasma cells, obliterative phlebitis, and storiform fibrosis. Involvement of several organs such as the pancreas, gastrointestinal tract, salivary glands, periorbital tissue and lymph nodes has been described. Up to now, vascular involvement by IgG4-RD has been thought to be essentially confined to large vessels. We present a patient with small-vessel systemic vasculitis involving muscle, peripheral nerve and kidney (glomerulonephritis) in the context of IgG4-RD diagnosed on the basis of elevated serum IgG4+ concentrations and histologically consistent signs in all biopsied tissues. Thoracic and abdominal aortic aneurysms in addition to aortitis, suggestive of large-vessel involvement, were also present. This observation expands the spectrum of vascular involvement in the context of IgG4-RD and supports the inclusion of IgG4-RD in the category of vasculitis associated with systemic disorder.