Amyloid Myopathy as an Inclusion Body Myositis Mimic

Introduction: Amyloid myopathy is a rare presentation of systemic amyloidosis. Amyloid myopathy can be initially misdiagnosed as sporadic inclusion body myositis (IBM). Methods: We report 4 cases of amyloid myopathy clinically mimicking inclusion body myositis and initially thought to be phenotypically IBM by neuromuscular experts. Results: Case 1 is an 81-year-old woman who presented with distal arm and proximal leg asymmetric weakness (myopathy pattern 4). Case 2 is a 76-year-old man with primary systemic amyloidosis who presented with myopathy pattern 4 and progressive dysphagia for four years. Case 3 is an 82-year-old man with progressive myopathy pattern 4 weakness and swallowing difficulty. Case 4 is a 62-year-old man with progressive bilateral finger flexor weakness. Muscle biopsies in all 4 cases showed perivascular amyloid deposits Discussion: Amyloid myopathy may be clinically indistinguishable from IBM. Muscle biopsy is of critical importance in the evaluation of patients suspected to have IBM