Diagnostic and prognostic value of anti-cN1A antibodies in inclusion body myositis.

Inclusion body myositis (IBM) is an acquired idiopathic inflammatory myopathy more commonly seen in individuals aged above 50. Unlike other idiopathic inflammatory myopathies, there is no response to immunosuppression/immunomodulation. The lack of response to such therapies led the focus away from considering IBM as a purely immune-mediated condition. However, the discovery of antibodies against cytosolic 5'-nucleotidase 1A (cN1A) in patients with IBM has reinvig-orated interest in autoimmunity as a key role in its pathogenesis. Over the last decade different methods have been developed to detect anti-cN1A antibodies. There has been an interest in whether these assays can be utilised in the diagnosis of IBM. Furthermore, there has been focus on whether anti-cN1A antibodies can be used to prognosticate and predict the clinical phenotype in IBM. Anti-cN1A antibodies appear to have a high specificity and moderate sensitivity for IBM. There have been some exploratory clinicopathological associations described in seropositive IBM patients, but sample sizes in most studies have been small so far. Antibody testing is yet to be standardised; which somewhat limits our ability to draw robust conclusions from current investi-gations. In this article we review the literature on anti-cN1A antibodies and discuss whether they have a role in clinical practice.