Case ReviewLambert–Eaton Myasthenic Syndrome and Dermatomyositis With Anti–TIF1-gamma Autoantibody: A Unique Association of Autoimmune Neuromuscular Conditions Without MalignancyIsfort, Michael MD*; Mnatsakanova, Diana MD†; Oddis, Chester MD‡; Lacomis, David MD*,§Author Information *Department of Neurology, University of Pittsburgh Medical Center, Pittsburgh, PA; †Department of Neurology and Rehabilitation, University of Illinois at Chicago, Chicago, IL; ‡Division of Rheumatology and Clinical Immunology, University of Pittsburgh, Pittsburgh, PA; and §Department of Pathology (Neuropathology), University of Pittsburgh Medical Center, Pittsburgh, PA. Reprints: Michael Isfort, MD, Department of Neurology, The Ohio State Neurological Institute, 395 W. 12th Avenue, 7th Floor, Columbus, OH 43210 (e-mail: mcisf[email protected]). This case was previously presented in abstract/poster form at the 2019 American Academy of Neurology (AAN) meeting, May 9, 2019, Philadelphia, PA. The authors report no conflicts of interest. Journal of Clinical Neuromuscular Disease: March 2021 - Volume 22 - Issue 3 - p 164-168 doi: 10.1097/CND.0000000000000318 Buy Metrics Abstract Lambert–Eaton myasthenic syndrome (LEMS) is a presynaptic neuromuscular junction disorder, and dermatomyositis (DM) is an idiopathic inflammatory myopathy. LEMS and DM are uncommon conditions that can present similarly and are often associated with autoantibodies. Concomitant LEMS and DM have only been reported a few times, and most of those cases were paraneoplastic. We present the first reported case of a patient with antivoltage gated calcium channel antibody positive LEMS who subsequently developed DM with antitranscription intermediary factor 1-gamma (anti–TIF1-γ) antibodies. Interestingly, both conditions occurred without evidence of malignancy. This diagnosis of LEMS and DM with characteristic clinical, electrodiagnostic, and histopathological evidence led to a beneficial modification of the patient's therapeutic regimen. Due to the fact that overlapping concurrent neuromuscular conditions are rare, a high clinical suspicion is needed to identify, evaluate (including appropriate cancer screenings), and appropriately treat these patients. Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.