Monoclonal gammopathy with both nemaline myopathy and amyloid myopathy

•We report a monoclonal gammopathy patient with nemaline and amyloid myopathy.•Muscle biopsy revealed interstitial amyloid deposition and clusters of rods.•Immunohistochemistry revealed sarcolemmal immunoreaction for the kappa light chain.•The patient responded well to intravenous immunoglobulin (IVIG) and prednisone.

Monoclonal gammopathies due to plasma cell dyscrasias can induce diverse rare neuromuscular disorders. Deposition of monoclonal antibody light chains in skeletal muscle causes amyloid myopathy. Monoclonal gammopathy is occasionally associated with sporadic late-onset nemaline myopathy. Here we report a monoclonal gammopathy patient with both sporadic late-onset nemaline myopathy and amyloid myopathy. The diagnoses were based on immunofixation electrophoresis of urine, and serum for free light chain assay, Congo red staining and Thioflavin S staining of muscle biopsies, as well as immunohistochemical staining and electron-microscopic observation. Nemaline myopathy and amyloid myopathy can present in the same patient with monoclonal gammopathy.