Inflammatory myopathy associated with myasthenia gravis with and without thymic pathology: Report of four cases and literature review

•It is important to recognize the association of myositis and MG and the different pattern of involvement of different components of the muscle and neuromuscular transmission, not only for a better understanding of both disorders, but also to comprehend and predict difficulties in the treatment.•This association should raise the suspicion of a thymoma.

IntroductionThe association of myasthenia gravis (MG) and inflammatory myopathy is rare and often only one of the diseases is diagnosed. Thymus pathology may be in the origin of such disease association.MethodsWe described four patients with both MG and inflammatory myopathy.ResultsThese cases correspond to 2.3% of our MG cohort. Case 1: MG, polymyositis and thymolipoma; case 2: MG and necrotizing myopathy without thymic pathology on a background of scleroderma, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, telangiectasia (CREST); case 3: MG and dermatomyositis without thymic pathology; case 4: MG and dermatomyositis with type C thymoma.DiscussionThe recognition of these neuromuscular co-morbidities contributes to (i) understanding their pathogenic mechanisms, (ii) developing better management approaches and (iii) further improving disease outcomes.