Objectives Myopathy as the presenting symptom from an ANCA positive vasculitis is uncommon. Vasculitis secondary to Crohn’s disease is an equally uncommon phenomenon. We report the first case of Crohn’s associated ANCA positive vasculitis causing a subacute proximal myopathy as the initial clinical manifestation. We also highlight the clinical improvement following institution of rituximab as rescue therapy.
Case A 27 years old female with recently diagnosed active Crohn’s disease presented with a 9 months history of progressive proximal upper and lower limb weakness. She had been treated with a course of steroids 6 months prior. She denied any constitutional symptoms. Examination revealed proximal muscle wasting and weakness in both upper and lower limbs. Positive investigations included a positive ANCA with high PR3 titre and a muscle biopsy demonstrating probable vasculitis. She was diagnosed with myopathy secondary to Crohn’s associated ANCA-positive vasculitis. She was treated with adalumimab and then infliximab which was upgraded to rituximab as rescue therapy when there was no response. The rituximab led to significant improvement to her weakness clinically.
Conclusions Vasculitis should be considered as a differential diagnosis for subacute myopathy in patients with an inflammatory or autoimmune phenotype. Muscle biopsy and ANCA immunofluorescence and titres are useful investigations. Whilst there is a lack of established evidence about the ideal agent for treating Crohn’s associated vasculitis, case reports suggest using TNF-alpha inhibitors or rituximab.