IgG4-related disease manifesting as sclerosing orbital inflammation and cutaneous pseudolymphoma with crystal-storing histiocytosis

A 69-year-old man presented with swelling of the left lower eyelid, proptosis and a history of erythematous scalp nodules. A CT scan revealed a mass involving the left inferior orbit and both lacrimal glands. Laboratory tests revealed peripheral blood eosinophilia and an elevated concentration of serum IgG. Orbital biopsy showed a fibro-inflammatory lesion with plasma cells and eosinophils. The largest scalp nodule was a fibro-inflammatory mass containing lymphoid follicles, plasma cells and eosinophils, as well as CD68-positive cells with eosinophilic, granular cytoplasm. In both lesions plasma cells were polyclonal and expressed IgG and IgG4. Treatment with prednisone and azathioprine resulted in a dramatic reduction in orbital swelling and resolution of the scalp nodules. After 8 months treatment was changed to tamoxifen with no recurrence of orbital disease but intermittent small scalp lesions. Sclerosing orbital inflammation and cutaneous pseudolymphoma have been recognized as IgG4-related diseases. Crystal-storing histiocytosis has been described in inflammatory and neoplastic proliferations of plasmacytoid cells but not in the setting of IgG4-RD. Tamoxifen has been used to treat idiopathic retroperitoneal fibrosis and may be useful for other lesions of IgG4-RD.