Objective: To introduce three new cases of Parkinson’s disease (PD) patients who developed Myasthenia gravis (MG) and to review clinical features and diagnostic approaches of previously reported cases, highlighting the importance of a rationalized use of laboratory and neurophysiological tests in PD patients with MG symptoms.

Background: MG is an autoimmune disease caused by the presence of antibodies against components of neuromuscular junction, presenting with muscular fatigue and ocular symptoms. PD is a neurodegenerative disorder featured by resting tremor, rigidity and bradykinesia. Such association is a rare condition and to our knowledge, only few cases describing the co-existence of PD and MG have been reported in literature. We highlight the usefulness of single-fiber electromyography (SFEMG) in PD patients complaining of isolated ocular or neck extensor symptoms.

Methods: We report 3 new cases of PD patients who developed MG, comparing the different diagnostic approaches to MG in PD patients. A systematic review of the literature was performed. The MEDLINE database, available through PubMed web-site, has been queried using “Parkinson” and “Myasthenia” as key words. The search was limited considering only papers describing an association between the two disease.

Results: We found 8 case reports and 2 case series: globally 14 patients have been described. Diagnosis of MG is based on classic finding, as RNS, SFEMG, neostigmine and edrophonium test. The presence of a-AChR is diagnostic of the disease. However, 50% of ocular MG is a-AChR negative. Fatigue could be considered one of the most common symptoms of PD. Nevertheless, PD patients do not have alterations at neuromuscular level and those with a pathological SFEMG could be affected by MG. Therefore, PD patients who showed clinical features of MG should undergo a dosage of a-AChR and, if it results negative, SFEMG on at least two different muscles should be advisable to make diagnosis of MG.

Conclusions: Common clinical features of PD and MG could delay the diagnosis of MG, therefore MG should be suspected in a PD patient as the association of the two diseases is possible. Moreover treatment of neuromuscular transmission dysfunction could prevent complications for deterioration of PD patients. The pathogenetic mechanism underlying the comorbidity is still unknown and further studies are necessary to understand the etiopathogenesis of PD and MG.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/is-it-just-a-coincidence-three-new-cases-of-parkinsons-disease-associated-with-myasthenia-gravis/