Abstract
BackgroundMyasthenia gravis is an autoimmune neuromuscular disorder, which has only rarely been reported to co-manifest with myositis. The diagnosis of concomitant myositis in patients with myasthenia gravis is clinically challenging, and requires targeted investigations for the differential diagnosis, including EMG, autoantibody assays, muscle biopsy and, importantly, imaging of the mediastinum for thymoma screening.Case presentationThis report presents a case-vignette of a 72-year-old woman with progressive proximal muscle weakness and myalgias, diagnosed with thymoma-associated myasthenia and bioptically verified granulomatous myositis, with positive autoantibody status for ryanodine receptor and titin antibodies.ConclusionsThe diagnosis of concurrent myositis and myasthenia gravis, especially in the presence of ryanodine receptor and titin antibodies, should lead neurologists to adopt different treatment strategies compared to those applied in myasthenia or myositis alone. Moreover, further evidence is warranted that titin and, particularly, ryanodine receptor antibodies may co-occur or be pathophysiologically involved in myasthenia-myositis cases.
Highlights
Myasthenia gravis is an autoimmune neuromuscular disorder, which has only rarely been reported to co-manifest with myositis
Further evidence is warranted that titin-Ab and, Ryanodine receptor (RyR)-Ab may be associated with Myasthenia gravis (MG)-myositis cases
This report presents a case of histologically verified granulomatous myositis (GrM) and thymoma - associated MG with positive Anti-acetylcholine receptor (AChR)-Ab, titin-Ab and RyR-Ab
Summary
This report presents a case of histologically verified GrM and thymoma - associated MG with positive AChR-Ab, titin-Ab and RyR-Ab. GrM is a rare, inflammatory neuromuscular disorder, histologically characterized by the development of non-specific, epithelioid granulomas in striated muscle. Titin-Ab and RyR-Ab have a 70 % positive predictive value, and 95 % sensitivity and specificity for a thymoma in MG [4] These striational antibodies have been repeatedly associated with thymoma-MG or severe, late-onset MG cases; their pathogenetic role in disease processes has, yet, not been clearly elucidated [11]. Given that in patients with MG - in contrast to myositis - initiation of therapy with high-dose steroids may exacerbate muscle weakness, in cases with concomitant manifestation of both disorders, a low-dose initiation of steroids with gradual titration, and concurrent administration of anticholinesterase agents, such as pyridostigmine, should be considered [6]
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