Idiopathic Brachial Neuritis in a Patient with Multiple Myeloma.

Idiopathic Brachial Neuritis (IBN), is a rare brachial plexopathy with an unknown aetiology. Multiple myeloma is a neoplastic plasma cell disease characterised by bone lesions. In this article, we present the case of a 59-year-old male patient with IBN associated with multiple myeloma, who was admitted to our clinic with right shoulder pain and right arm weakness. He experienced muscle weakness and atrophy in his right arm after a sudden onset of pain attack in the shoulder. Plexus and cervical vertebral MRI showed no pathology. Electrodiagnostic studies showed upper and middle trunk plexopathies. Laboratory analysis revealed anaemia, hypercalcaemia, renal dysfunction and monoclonal gammopathy in immunoglobulin electrophoresis. A bone marrow biopsy established the diagnosis of IgG kappa multiple myeloma. This is the first case report that presents the association of multiple myeloma and IBN.