Orbital amyloid tumor associated with myasthenia gravis.

We present a case of a 53-year-old female with an 11 year history of myasthenia gravis (MG) with palpebral ptosis in the left eye which had become more marked over the previous year. Examination revealed a painless left orbital mass causing ptosis. The tumor was surgically removed and histopathology revealed deposits of a hyaline substance which when stained with Congo Red had an apple-green birefringence with polarized light, typical of amyloid. In the absence of amyloid deposits elsewhere in the body, amyloid tumor (AT) was diagnosed. No myelo- or lymphoproliferative syndromes, systemic involvement by amyloidosis or any autoimmune disease were found. The evolution and aesthetic results where satisfactory. Only two cases of orbital AT associated with MG have been described previously; however, in one of the cases, the symptoms of the AT had led to a false diagnosis of MG.