DON’T JUDGE A BOOK BY ITS COVER: UNUSUAL CASE OF MYASTHENIA GRAVIS

Abstract

SESSION TITLE: Medical Student/Resident Pulmonary Manifestations of Systemic Disease Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Myasthenia gravis is an autoimmune disorder where auto-antibodies bind to the acetylcholine receptors present in the post-synaptic membrane of the neuromuscular junction. It typically presents with limb weakness but may also include ocular symptoms such as diplopia and ptosis or bulbar symptoms including dysphagia, dysphonia and dysarthria. We report an atypical case of myasthenia gravis that initially appeared to be consistent with the diagnosis of asthma. CASE PRESENTATION: The patient is a 78-year old female with a past medical history of remote deep venous thrombosis associated with pulmonary embolism, hypertension, rheumatoid arthritis, and polymyalgia rheumatica who was referred to pulmonology for eight months of exertional dyspnea and fatigue. Besides her progressive dyspnea, additional respiratory symptoms included chest tightness, non-productive cough, and wheezing. Her pulmonary function tests indicated a mixed obstructive and restrictive defect with FEV1/FVC ratio of 69% with FVC of 1.63L (62 % predicted) as well as a positive bronchodilatory response. She was started on a regimen of ICS/LABA, leukotriene inhibitor, and an as needed ß2-recptor agonist for presumed late-onset asthma in which her symptoms only partially improved. Given both the severity of her dyspnea and restrictive physiology on her pulmonary function testing in absence of parenchymal lung disease, the patient underwent additional neuromuscular evaluation. Her maximal inspiratory pressure (MIP) was 15% predicted and her maximal expiratory pressure (MEP) was 16% predicted in setting of a normal diaphragmatic fluoroscopy (SNIFF test). She subsequently underwent serological evaluation for neuromuscular weakness in which her acetylcholine binding antibody was positive, confirming the diagnosis of myasthenia gravis. The patient was started on acetylcholinesterase inhibitor and steroids with a mixed response. Due to progression of her illness, she eventually required ICU admission and was started on plasmapheresis with positive clinical response. DISCUSSION: Acetylcholine receptor antibody myasthenia gravis has a bimodal pattern with early onset prior to age of 50. It uncommonly can be seen in setting of other autoimmune disorders such as systemic lupus, thyroiditis, or as seen in our patient, rheumatoid arthritis. Our case is unique given the fact that patient initially presented with clinical features suggestive of late-onset asthma. However, given only partial improvement in symptoms and unexplained restrictive physiology on spirometry, further testing revealed diagnosis of myasthenia gravis. CONCLUSIONS: This case stresses the need for thorough evaluation for all patients with unexplained progressive dyspnea. Reference #1: Gilhus NE. Myasthenia Gravis. Longo DL, ed. N Engl J Med. 2016;375(26):2570-2581. doi:10.1056/NEJMra1602678 Reference #2: Marlowe FI, D’Angelo AJ. Respiratory failure as the initial presentation of myasthenia gravis. Ear Nose Throat J. 1989;68(6):472-473. Reference #3: Qureshi AI, Choundry MA, Mohammad Y, et al. Respiratory failure as a first presentation of myasthenia gravis. Med Sci Monit. 2004;10(12):CR684-689. DISCLOSURES: No relevant relationships by Shubham Adroja, source=Web Response No relevant relationships by Anthony Cucci, source=Admin input No relevant relationships by Urbee Haque, source=Web Response