Case reportClinical, neuropathological and radiological evidence for a rare complication of rituximab therapy

•Anti CD 20 therapy may result in unusual infections.•We report enterovirus myofasciitis with documented pathology for the first time.•Increased susceptibility to rare viruses should be considered in treated patients.•Echovirus related muscle disease manifests as myofasciitis not dermatomyositis.•Successful treatment can be considered as discussed in this report.

We report a rare case of myofasciitis and meningitis with deafness caused by systemic enterovirus infection in the setting of hypogammaglobulinaemia induced by rituximab. Whilst effective and generally safe, anti- CD 20 antibody therapy is increasingly recognised to result in unusual infectious complications to be considered in a treated patient presenting with neurological symptoms. These cases may pose diagnostic difficulties and can have atypical presentations. We present this rare complication of rituximab therapy, with histopathological confirmation of myofasciitis. In the older literature, enterovirus associated myofasciitis may have erroneously been termed dermatomyositis and we review the literature to demonstrate this important nosological point.