A newly published study in Acta Neurologica Belgica reveals that the presence of acetylcholine receptor antibodies (AChR Ab) and abnormal single-fiber electromyography (SFEMG) in myasthenia gravis (MG) is interrelated with ongoing clinical findings, necessitating drug treatment.

MG is an antibody-mediated autoimmune disorder defined by variable and fatigable weakness. MG with restricted ocular indications is termed ocular myasthenia gravis (OMG). Studies have shown that 50%–60% of OMG patients progress to generalized myasthenia gravis (GMG) within 2 years of symptom onset.

AChR Ab seropositivity in patients suffering from GMG is reported to be approximately 80%–90%, while antibodies channelized against the protein muscle-specific tyrosine kinase (MuSK Abs) constitute 5%–8%. Meanwhile, seropositivity in patients suffering from OMG is comparatively lower, ranging between 40% and 70% for AChR Ab. 

SFEMG has reported an OMG sensitivity of about 80%. The presence of thymoma is rarely detected in OMG. Acetylcholinesterase inhibitors are accepted as the preferred treatment for OMG. Thymectomy is usually reserved for patients suffering from thymoma in OMG.

“Here, we tried to evaluate if there are clinical and laboratory features at onset of the disease predicting response to treatment in these patients. Demographic features, neuro-ophthalmologic findings at onset, AChR Ab, MuSK Ab seropositivity, thymic status, SFEMG results were the variables taken into consideration,” the authors highlighted.

Read more about myasthenia gravis diagnosis

The research team included patients diagnosed with OMG between 2010 and 2021 in the Neuro-ophthalmology Clinic of Ege University Medical School Department of Neurology, Izmir, Turkey. A total of 108 patients were followed for over 36 months.

Study results reported the average age of disease onset to be 57 years, while the clinical features at onset were reported to be isolated ptosis in 55 patients and isolated diplopia in 33 patients. Additionally, combined ptosis and diplopia were reported to be present in 20 patients.

Furthermore, 66 patients reported AChR Abs, whereas only two had MuSK Abs. SFEMG abnormality was reported in 74 patients, while 16 exhibited thymoma and 6 showed thymic hyperplasia. A total of 41 patients were treated with pyridostigmine alone, while 67 patients were given immunosuppressive drugs. Thymectomy results reported complete stable remission (CSR) in 49 patients, while 59 patients had reached the minimal manifestation (MM) status.

A comparison of patients with CSR and MM status revealed that the presence of AchR Abs and an abnormal SFEMG was linked with the ongoing clinical findings requiring treatment.

“In conclusion, prognosis of our OMG patients was favorable, nearly half reaching CSR and the other half showing minor features under low-dose treatment. AchR Ab seronegativity and normal SFEMG at onset were the factors associated with stable remission in the absence of any medication,” the authors concluded.

Reference

Çelebisoy N, Orujov A, Balayeva F, et al. Prognostic predictors of remission in ocular myasthenia gravis. Acta Neurologica Belgica. Published online December 6, 2022. doi:10.1007/s13760-022-02151-4