Objective: To evaluate the clinical features of patients with Parkinson’s Disease (PD) with versus without comorbid Myasthenia Gravis (MG).

Background: The recognition of the co-occurrence of myasthenia gravis (MG) in Parkinson’s Disease (PD) is challenging, given the symptomatic overlap.

Method: We designed a multi-center case-control study selecting patients with a diagnosis of PD based on UK brain bank criteria and MG based on clinical, electrophysiological and immunological features (PD-MG) as cases and age- and gender-matched PD-only patients as controls. We evaluated demographics, family history, motor and non-motor symptoms, laboratory and electrophysiological data, and medication use. PD severity was assessed by Hoehn and Yahr stage and UPDRS motor scores.

Results: 14 PD-MG cases (79% males, 21% females; mean age 72.5 +/-8.4 years) were compared to 14 PD-only controls. Duration of PD symptoms, time to diagnosis, disease stage, and daily levodopa equivalent dose were similar in cases and controls. Tremor was the predominant presenting phenotype in both groups. Dysphagia was more frequently reported in PD-MG than PD-only patients (p=0.04). PD-MG cases included 8 with generalized MG, 4 ocular, 1 bulbar and 1 combined. PD diagnosis predated MG in 35.7% whereas MG predated PD in 42.9% of cases; with 21.3% being diagnosed concurrently. MG diagnosis was confirmed by positive acetylcholine receptor antibodies (n=8) and electrophysiologic testing (n=8).  MG was under treatment in all PD-MG cases; PD in all but two patients in both groups. Two PD-MG cases required ICU admission and intubation for respiratory failure.

Conclusion: Comorbid MG in PD has rarely been described in the literature. Olfactory dysfunction, sleep disorders, and dysphagia can occur in PD and MG. While there were no differences in initial symptom presentation in PD-MG versus PD alone, dysphagia was more common in the PD-MG group. Dysphagia alone or with ptosis (“apraxia of eyelid opening”) or diplopia may represent clues for suspecting comorbid MG in patients with PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/comorbid-parkinsons-disease-and-myasthenia-gravis-a-case-control-study/