To analyze cases of polyneuropathy in inclusion body myositis (IBM) and to report three cases with inflammatory polyneuropathy.

Inclusion body myositis (IBM) is a progressive disabling myopathy of unknown etiology affecting proximal and distal muscles. There is a debate about the association of neuropathy in IBM because of its distal distribution of muscle weakness and EMG findings of neuropathic and myopathic features. Moreover, the etiology of IBM remains controversial; it is argued to be either a degenerative disease characterized by abnormal protein accumulation like beta-amyloid or primarily an autoimmune disorder characterized by inflammatory infiltrates.

We reviewed the records of 44 patients diagnosed with IBM in our center. 17 of whom had neuropathy with etiology were identified in the majority. A sural nerve biopsy was performed on three of the remaining individuals, where the cause of neuropathy was not recognized.

A muscle biopsy of 44 patients diagnosed with IBM showed inflammation and rimmed vacuoles. Of these, 17 patients had polyneuropathy. Most of these cases had identifiable causes of neuropathy like diabetes, vitamin deficiency, and others. Sural nerve biopsy in three of those with no identifiable cause of neuropathy was performed and showed demyelination, axonal degeneration, and inflammatory infiltration but no amyloid deposits.

Our study adds to the literature regarding the association of polyneuropathy with IBM. We identified three patients diagnosed with IBM who also exhibited inflammatory polyneuropathy, indicating that autoimmune etiology might be involved. However, the possibility of coincidental findings cannot be ruled out. This emphasizes that nerve biopsy can be a useful tool for patients presenting with IBM and neuropathy without a clear cause. Our findings highlight the need for further studies to explore the association and determine the extent to which the autoimmune mechanism contributes to this disorder.