PRIMARY LOCALIZED AMYLOIDOSIS OF THE ORBIT

Aims/background - Primary localised amyloidosis is rarely encountered in the orbit. The typical clinical and radiological appearances have n ot been clearly established, in particular the single site deposition of amyloid has never been proved. Methods - Six cases were reviewed in detail and their clinical and radiological characteristics are descri bed here. Four patients had scintigraphy with I-123 serum amyloid P co mponent and one patient had typing of the amyloid fibrils.Results - Al l the patients had a firm mass in the upper orbit with a predilection for the region of the lacrimal gland. Computed tomography showed a hom ogeneous mass with thickening and irregularity of the adjacent bone an d/or calcification within the mass. None was associated with systemic disease. Scintigraphy with I-123 serum amyloid P component demonstrate d that the amyloid was confined to the orbit. In one patient the amylo id fibrils were derived from an IgG4 heavy chain constant domain. The lesions were partially excised with subsequent clinical stability over 6 months to 18 years in all but one patient who had continued enlarge ment of the lesion. Conclusion - There is a characteristic clinical an d radiological pattern for primary localised amyloidosis of the orbit. The disease process is truly local and not part of a systemic process . A majority respond to simple debulking with subsequent observation.