Inclusions criteria are IM (as defined by the 119th European Neuromuscular Centre workshop) or generalised MG (as defined by the Texas Clinical Classification System) associated with specific AAbs (anti-synthetases (JO1, PL7 or PL12), or anti-SRP for primary IM, and anti-AchR for MG) and refractory to conventional treatments defined as an inadequate response to, or intolerable side effects with conventional treatments, such as corticosteroids, azathioprine, methotrexate, cyclophosphamide, cyclosporine, IgIV and/or plasma exchange.