Neuromyelitis optica spectrum disorders and their overlap with myasthenia gravis in a single center in Argentina.

BACKGROUND

The incidence of neuromyelitis optica spectrum disorder (NMOSD) in association with other autoimmune diseases is frequent. The coexistence of myasthenia gravis (MG) and NMOSD has been reported, showing a higher-than-expected likelihood of co-occurrence. The aim of this study is to describe the overlap between NMOSD and MG and to analyze these cases within two large real-world cohorts of patients with AQP4 antibody-positive NMOSD and AChR antibody-positive MG in Argentina.

METHODS

A cross-sectional, retrospective study was conducted at a referral center in Buenos Aires, Argentina, including patients with AQP4-Ab-positive NMOSD and AChR-Ab-positive MG.

RESULTS

A total of 389 medical records were reviewed: 108 NMOSD and 281 MG cases. Among them, 77 patients were AQP4-IgG positive, and 207 were AChR-Ab positive. Three out of 77 AQP4-IgG-positive patients had MG with AChR-Ab positivity, accounting for 3.89% of NMOSD cases. Conversely, three out of 207 AChR-Ab-positive MG patients (1.45 %) had AQP4-IgG-positive antibodies. Patients with concurrent MG and NMOSD were female, had a late onset of NMOSD, and experienced MG onset before NMOSD. They also showed a good response to NMOSD treatment with immunosuppressive therapy. Two patients had undergone thymectomy before NMOSD onset. No patient was receiving immunosuppressive treatment at the time of NMOSD onset.

CONCLUSIONS

A total of 3.89 % of AQP4-Ab-positive NMOSD patients had overlapping AChR-Ab-positive MG. This is the first report assessing the association between NMOSD and MG in Argentinian and Latin American (LATAM) patients.