Co-Occurrence of Facioscapulohumeral Muscular Dystrophy and Myasthenia Gravis: A Systematic Review and Meta-Analysis of Individual Patient Data.

BACKGROUND

Co-occurrence of facioscapulohumeral muscular dystrophy (FSHD) and myasthenia gravis (MG) is rare but clinically critical, as treatable MG symptoms may be misattributed to FSHD progression. This systematic review and meta-analysis aimed to comprehensively characterize patients with both conditions and to quantitatively synthesize the available individual patient data.

METHODS

Following PRISMA 2020 guidelines, we searched four databases until 3 April 2026 for original reports providing individual-patient data on confirmed FSHD and MG co-occurrence. We performed descriptive and quantitative syntheses of clinical, genetic, and therapeutic variables.

RESULTS

Nine studies were systematically reviewed, with 29 patients contributing to on. FSHD onset significantly preceded MG onset, with a pooled mean interval of 24.21 years. The pooled mean age at MG onset was 62.62 years. All tested patients were acetylcholine receptor antibody positive. MG frequently presented with ocular and bulbar manifestations. Crucially, the pooled estimate for clinical improvement following standard MG-directed therapies was 89.7%.

CONCLUSION

MG in FSHD patients typically emerges late in adulthood as an antibody-positive autoimmune synaptopathy. Recognizing new ocular or bulbar weakness as superimposed MG is essential, providing a highly treatable avenue to reverse functional decline in patients with established myopathy.