Key features:
(1) orbital pseudotumor
(3) variable presence of IgG4-related inflammation at other body sites
(4) increased numbers of IgG4 positive plasma cells
(5) elevated concentrations of IgG4 in the blood
(6) dense fibrosis which may be sclerosing and/or storiform
(7) exclusion of other autoimmune disorders (granulomatosis with polyangiitis, etc) and malignant lymphoma
Findings that distinguish IgG4-related disease from IOI (Monbaerts et al):
(1) IgG4-positive plasma cells > 30 cells per high power field
(2) serum IgG4 to total IgG ratio > 40%
In the series of Wu and Sun the patients with IgG4-related disease all had serum IgG4 concentrations greater than 0.4 g/dL (with one up to 4.3 g/dL).
Additional variable findings:
(1) enlargement of the infraorbital nerve
(2) bilateral lacrimal gland enlargement
(3) vision loss from compression of the optic nerve
(4) extraocular myositis with limited eye movement
(5) eyelid swelling
(6) eosinophilia with recurrent sinusitis
