Effect of intravenous immunoglobulin therapy on anti-NT5C1A antibody-positive inclusion body myositis after successful treatment of hepatitis C: A case report

Inclusion body myositis (IBM) is the commonest idiopathic inflammatory myopathy of older persons. Pathophysiological mechanism of IBM remains unknown; however, an association of IBM with chronic hepatitis C virus (HCV) infection and serum autoantibodies against skeletal muscle protein 5′-nucleotidase 1A (NT5C1A) has recently been reported. No effective treatment for IBM has yet been developed. We here present a 70-year-old man who was anti-NT5C1A antibody-positive in association with IBM and chronic hepatitis C. The initial treatment of ombitasvir/paritaprevir/ritonavir for his chronic hepatitis C was successful; however, his symptoms of IBM did not improve. On the contrary, his quadriplegic paralysis became more severe and he developed dysphagia. Next, steroid pulse therapy was initiated for IBM and, although his hyper-creatine phosphokinase-emia improved, his symptoms did not; indeed, they worsened. Subsequent intravenous immunoglobulin therapy (IVIg) resulted in obvious improvement in his dysphagia. Thereafter IVIg therapy was repeated at approximately 2-monthly intervals. His dysphagia remained improved for more than 1 year; however, his quadriplegia continued to progress slowly. Although IBM can reportedly be associated with hepatitis C, we inferred that there was no direct relationship between these conditions in our patient because his IBM did not improve after treatment of his hepatitis C. Although his IBM-associated quadriplegia did not improve, IVIg therapy did result in improvement in his dysphagia.