Amyloid myoneuropathy mimicking inclusion body myositis.

myopathy affecting proximal and distal musculature with typical onset of symptoms after age 50 years. Inclusion body myositis more often affects males and results in a classical pattern of early asymmetric weakness and wasting of forearm flexors (wrist and long finger flexors), quadriceps and ankle dorsiflexors. Inclusion body myositis is more frequently associated with a monoclonal gammopathy than is seen in the general population but the implications of this association remain unclear1. Importantly, there is no available therapy to slow disease progression in IBM. Primary systemic amyloidosis (AL) typically results in light chain deposition in the tongue, kidneys, heart, liver, spleen and peripheral nerves with accompanying respective clinical sequelae. Rarely, light chain deposition can focally involve components of the nervous system. Peripheral nerve complications include carpal tunnel syndrome, dysautonomia and polyneuropathy2,3. Amyloid myopathy is rare and typically demonstrates proximal muscle involvement and electrophysiological findings indistinguishable from the inflammatory myopathies4. Prompt differentiation of amyloid myopathy from the inflammatory myopathies is essential as AL may respond to chemotherapy resulting in improved progression free survival5. We report a case of AL presenting with predominant myopathy clinically suggestive of IBM and with similar findings on initial muscle biopsy, an important distinction in light of recent treatment advances in AL.