Teaching NeuroImages: Neuromyopathy in a patient with hereditary transthyretin Thr60Ala amyloidosis

A 69-year-old man with hereditary transthyretin (hATTR) Thr60Ala amyloid cardiomyopathy presented with a 2-year history of proximal greater than distal weakness and pan-modality sensation loss in the lower extremities. Nerve conduction studies/EMG revealed a proximal myopathy and length-dependent axonal polyneuropathy. Muscle biopsy was diagnostic of amyloid myopathy (figure) and skin biopsy showed large amyloid deposits but normal intraepidermal nerve fiber density (figure). Myopathy is rare in hATTR amyloidosis and concomitant polyneuropathy is always present.¹ Skin biopsy is less invasive than nerve biopsy and has good sensitivity for amyloid diagnosis.² hATTR amyloidosis is treatable and should be included in the differential diagnosis of a neuromyopathy.