Light-chain amyloidosis mimicking giant cell arteritis in a bilateral anterior ischemic optic neuropathy case

Background: Herein we report a case of bilateral anterior ischemic optic neuropathy (AION) showing histopathologic evidence of AL-amyloidosis of the temporal arteries. It is known that light-chain (AL) amyloidosis may rarely affect the temporal arteries, mimicking giant cell arteritis, while, to our knowledge, the association between AL-amyloidosis and AION was not previously described. Case presentation: A 64 year-old woman with AL-amyloidosis secondary to a monoclonal gammopathy of undetermined significance (MGUS) referred to our hospital for acute painless drop of vision due to bilateral AION. Age greater than 50 years, high erythrocyte sedimentation rate (ESR), and bilateral AION were suggestive of giant cell arteritis (GCA). However, a temporal artery biopsy excluded GCA, showing segmental stenosis of the lumen caused by amyloidosis of the artery wall. Conclusions: The present case shows that AL-amyloidosis may present with AION, high ESR, and temporal artery involvement, mimicking GCA. In patients with monoclonal gammopathies, C-reactive protein may be a more specific index of GCA compared with the ESR. Patient medical history and pathology are crucial for a correct diagnosis.