Objective: We present a unique clinical case of antibody positive Muscle Specific Kinase (MuSK) Myasthenia Gravis and DaT scan positive Parkinson’s Disease to highlight the overlapping nature of clinical symptoms and challenges seen in clinical diagnosis.

Background: The concomitant diagnosis of Myasthenia Gravis (MG), an autoimmune condition that affects the neuromuscular junction, and Parkinson’s disease (PD), a neurodegenerative disease that affects the basal ganglia, is remarkably exceptional. Furthermore, there are very few case reports in the literature that have recognized muscle-specific kinase (MuSK), a subtype of MG, with overlapping features of PD^1,2. We present a unique case of MuSK MG and DaT scan positive Parkinson’s Disease, which to our knowledge has not been previously reported.

Method: Case report

Results: 49-year-old male initially presented to neurology clinic with six months of waxing and waning nasal quality dysarthria. After thorough workup with serologic and electrophysiologic studies, patient was diagnosed with seropositive bulbar predominant MuSK Myasthenia Gravis for which steroid sparing immunosuppressive treatment was initiated with mycophenolate mofetil. He subsequently developed clinical exam findings of hypomimia, bilateral bradykinesia, asymmetrical limb rigidity, right arm and jaw tremor that raised concern for the possibility of parkinsonism. Review of systems for premotor symptoms was positive for constipation and dream enactment behavior. There was no previous exposure to anti-dopaminergic therapies and MRI Brain was unrevealing. DaT scan was subsequently obtained, which demonstrated objective evidence of bilateral striatal dopaminergic deficiency, indicative of an inherent basal ganglia disorder. In the absence of any clinical findings of atypical parkinsonism, patient met clinical diagnostic criteria for Idiopathic Parkinson’s Disease.

Conclusion: This case demonstrates the clinical challenges that are present in this overlap of neuromuscular and neurodegenerative disease in a single individual. We highlight the importance of a thorough history and physical examination, supported with objective evidence by a positive DaT scan, to elucidate the appropriate etiology of symptoms.

References: 1. Lanfranconi S, Corti S, Baron P, Conti G, Borellini L, Bresolin N, Bersano A: Anti-MuSK-positive myasthenia gravis in a patient with parkinsonism and cognitive impairment. Neurol Res Int. 2011, 2011:859802.

2. Albassam MS, Thabet SA, Hmoud M, Makkawi S. Anti-Muscle Specific Kinase (Anti-MuSK) Positive Myasthenia Gravis Overlapping With Parkinson’s Disease: A Challenging Diagnosis. Cureus. 2021 May 4;13(5):e14839. doi: 10.7759/cureus.14839. PMID: 34104586; PMCID: PMC8174120.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/dat-scan-positive-parkinsons-disease-in-a-patient-with-anti-musk-positive-myasthenia-gravis/