Co-occurrence of systemic lupus erythematosus and myasthenia gravis: Insights from a cross-sectional cohort.

OBJECTIVE

Myasthenia gravis (MG) and systemic lupus erythematosus (SLE) share immunopathogenic mechanisms, yet their co-occurrence remains poorly characterized, particularly in non-Western populations. This study investigated SLE prevalence in Egyptian Patients with MG and examined the role of thymectomy in triggering systemic autoimmunity.

METHODS

This cross-sectional observational study enrolled 50 consecutive Patients with MG at Mansoura University Hospital, Egypt (April 2024-January 2025). All patients underwent comprehensive clinical evaluation, serological testing (ANA, anti-dsDNA, anti-AChR), and rheumatologic assessment. SLE diagnosis followed ACR revised criteria. Pre- and post-thymectomy inflammatory markers were compared using paired statistical tests.

RESULTS

SLE was identified in 18% (9/50) of Patients with MG, substantially higher than Western population estimates (0.9-1.4%). SLE-positive patients required significantly higher corticosteroid doses despite shorter treatment duration (p < 0.001). Among 21 thymectomized patients with no pre-operative autoimmune features, 42.9% developed cutaneous manifestations, 33.3% arthritis, and 28.6% became ANA-positive post-operatively. Median ESR increased significantly from 20 to 35 mm/hr following thymectomy (p < 0.001).

CONCLUSION

SLE is highly prevalent among Egyptian Patients with MG and is associated with a more refractory clinical course. Thymectomy appears to precipitate systemic autoimmunity and inflammation, necessitating long-term post-operative rheumatologic surveillance, particularly in genetically susceptible populations.