[Primary AL-type amyloidosis disclosed by Horton disease].

Primary systemic amyloidosis rarely affects the walls of small and medium-sized vessels. We report a case of primary AL amyloidosis masquerading as giant cell arteritis at the onset of the disease, revealed by the temporal arteritis biopsy, and successfully treated by corticotherapy for three years. Histology of temporal arteritis confirms the diagnosis of amyloidosis (characteristic birefringence with Congo red). We discuss in this case the diagnosis of primary amyloidosis revealed by Horton disease, or the coincidental association of these two diseases.