Severe proximal muscle weakness with normal CK as a presenting feature of ANCA-associated vasculitis.

Antineutrophil cytoplasmic antibodies associated vasculitis (AAV) presenting with muscle weakness is rarely reported. We report a case of myeloperoxidase positive vasculitis presenting with severe proximal muscle weakness with normal creatine kinase and no positron-emission tomography uptake. There was a significant delay in the diagnosis of AAV due to atypical presentation. We propose AAV be considered in the differential diagnosis of proximal muscle weakness after excluding the common causes.