Complications of Long COVID: Unraveling a Case of Very-Late-Onset Myasthenia Gravis

Myasthenia gravis (MG) is defined as an autoimmune neuromuscular disorder where autoantibodies disrupt synaptic transmission at the neuromuscular junction by targeting the acetylcholine receptor (AChR), muscle-specific kinase (MuSK), or other proteins related to the AChR complex. This disruption leads to characteristic muscle weakness and rapid fatigability. Clinically, MG is classified based on the age of onset into three distinct categories: early-onset MG (younger than 50 years), late-onset MG (between 50 and 64 years), and very-late-onset MG (65 years and older). We present a rare case of an 81-year-old man who presented with dysarthria, shortness of breath, diplopia, and oropharyngeal dysphagia to both solids and liquids for approximately seven days and was noted to be more progressive in the last 48 hours prior to his presentation to the emergency room. Upon arrival at the emergency room, he complained of shortness of breath and diplopia. Of note, approximately four months prior to this admission, he was diagnosed with COVID-19 pneumonia and was treated appropriately with remdesivir and corticosteroids. He had an uneventful COVID-19 pneumonia hospitalization and was discharged home. Given the progressive nature of his symptomatology, particularly dyspnea, he was transferred to the ICU for further evaluation and treatment. Laboratory results were positive for AChR binding, blocking, and modulating antibodies, confirming the diagnosis of MG. The patient received treatment consisting of pyridostigmine, a pulse dose of methylprednisolone, and intravenous immunoglobulin (IVIG) therapy. This case is unique and highlights a case of a very late onset of MG and the manifestation of new-onset MG four months following COVID-19. Additionally, this patient had a very delayed onset of MG symptoms, as he presented four months after his infection with COVID-19, compared to the average onset of reported cases of post-COVID MG being four to eight weeks post-infection with COVID-19. This uniquely delayed onset, occurring beyond a three-month window post-COVID-19 infection, aligns with the criteria established by the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) for a diagnosis of "Post-COVID Condition," also known as "Long COVID." This case illustrates the intricate link between post-viral states and autoimmune responses, particularly in geriatric patients. The pathophysiology linking COVID-19 to MG primarily involves immune dysregulation triggered by the viral infection, which may disrupt immune tolerance and lead to clinical autoimmunity. This case stresses the need for vigilance in diagnosis and managing neurological complications in the context of viral respiratory illnesses, particularly in vulnerable populations.