2025 American Academy of Neurology Abstract Website

Francesca Beretta¹, Ebe Schiavo¹, Melania Guida², Alba Cepele², Carmen Erra³, Pietro Businaro⁴, Paolo Emilio Alboini⁵, Fabio Maria Della Cava⁶, Claudia Vinciguerra⁷, Matteo Gastaldi⁸, Gregorio Spagni¹, Luca Massacesi¹, Francesco Habetswallner³, Michelangelo Maestri Tassoni², Amelia Evoli⁹, Valentina Damato¹
¹NEUROFARBA, University of Florence, ²Department of Clinical and Experimental Medicine, University of Pisa, ³Neurophysiopathology Unit, AORN Cardarelli, ⁴Department of Brain and Behavioral Sciences, University of Pavia, ⁵Neurology Unit, IRCCS Casa Sollievo della Sofferenza Foundation, ⁶Neurology and Stroke Unit, ASL1 Liguria, ⁷Neurology Unit, University Hospital San Giovanni di Dio e Ruggi D’Aragona, ⁸IRCCS Mondino Foundation, ⁹Department of Neuroscience, Catholic University, Neuroscience Dept

Objective:

To assess serologic and clinical characteristics of seronegative myasthenia gravis (SNMG) patients in a multicenter Italian cohort.

Background:

MG is an antibody-mediated autoimmune disorder affecting neuromuscular transmission. About 10-15% of patients are seronegative when tested by standard assays, of whom up to 30% harbour low-binding conformational autoantibodies detected by live cell-based assays (L-CBA).

Design/Methods:

MG patients who tested negative to radioimmunoassay or enzyme-linked immunosorbent assay for autoantibodies to acetylcholine receptor (AChR) or muscle-specific kinase protein (MuSK) were included; neurophysiologic findings of impaired neuromuscular transmission or a positive response to acetylcholinesterase inhibitors were required to support clinical diagnosis.

Sera were tested by L-CBA for autoantibodies to clustered adult-(A)-AChR, fetal-(F)-AChR, MuSK and lipoprotein-receptor-related protein 4 (LRP4).

Results:

A total of 156 patients were recruited from seven Italian Referral Centers: most were females (n=89) and had an early-onset phenotype (n=93). L-CBA was positive in 25/156 patients: 21 AChR, of whom 12 showed reactivity for either A-(5) or F-AChR (7) isoforms, and 4 MuSK. There were no LRP4 positive sera.

We found no differences between SNMG patients and patients seropositive after L-CBA when considering disease severity (maximum MG Foundation of America class; p=0.42, Fisher’s exact test) or outcome (post-intervention status; p=1, Fisher’s exact test). Diagnosis of SNMG was heterogeneous among different Centers, with several not requiring suggestive neurophysiology for diagnosis (n=64 negative test/not performed; n=9 data not available).

Conclusions:

Our study confirms that L-CBA offers a diagnostic gain compared to standard assays and supports its use in the second-line screening of SNMG patients. Nonetheless, we raise the question of the real utility of LRP4 testing.

The high proportion of triple-SNMG patients to L-CBA and the lack of an alternative biomarker underlines the importance of well-defined clinical/electromyographic diagnostic criteria. Further research is warranted to better define the clinical characteristics of SNMG and help designing specific diagnostic and management guidelines.