Orbital inflammatory pseudotumor due to hypersensitivity vasculitis and mononeuritis multiplex in a patient with atypical, cANCA-positive Wegener's granulomatosis

We report on a 60-year-old woman with a retro-orbital pseudotumor and polyneuropathy. The retro-orbital inflammation was histologically diagnosed as hypersensitivity vasculitis (HV). As cytoplasmatic antineutrophilic cytoplasmatic antibody (cANCA) and anti-proteinase-3 antibody were detected, the differential diagnosis also included atypical Wegener's granulomatosis. Hypersensitivity vasculitis is defined as small-vessel vasculitis mediated by the deposition of immune complexes (Arthus reaction) after exposure to various agents such as drugs, toxins, and infections. Since an inflammatory retro-orbital pseudotumor due to HV has not previously been reported, the following case is presented.

Magnetic resonance imaging (MRI) revealed retro-orbital infiltrate without granuloma. Histology from an orbital biopsy confirmed HV. Electromyography was used for the diagnosis of polyneuropathy. Serum investigation indicated erythrocyte sedimentation rate (ESR) >100 mm/h, C-reactive protein (CRP) 223 mg/l, antinuclear antibodies 1:80, and cANCA 100 U/ml.

The bilateral orbital pseudotumor, polyneuropathy, and serum levels of inflammation reactants (ESR and CRP) improved from therapy with corticosteroids (1 g of methylprednisolone initially) and azathioprine (150 mg/day).

Because of cANCA and anti-proteinase-3 antibody positivity, this case can be viewed more as an atypical Wegener's granulomatosis than a systemic HV. The causal variety of inflammatory orbital pseudotumor, including HV and different therapeutic consequences, requires histological differentiation from usual orbital pseudotumors.