Myasthenia gravis with dysphagia as the first symptom and misdiagnosed as anxiety-depressive state: a case report.

Background: Myasthenia gravis (MG) is a rare autoimmune disorder that affects the neuromuscular junction, with a global prevalence of approximately 30 cases per 100,000 individuals. Although dysphagia occurs as an initial symptom in 6%-15% of patients, isolated dysphagia as the sole presenting and predominant manifestation is exceedingly rare, posing a significant diagnostic challenge. Furthermore, a complex bidirectional relationship exists between dysphagia and psychiatric conditions such as anxiety and depression, which often leads to misdiagnosis. Approximately 20% of patients with MG are refractory to conventional immunosuppressive therapy. The novel FcRn antagonist efgartigimod rapidly and sustainably reduces pathogenic IgG levels, providing a new therapeutic option for refractory generalized MG. Case presentation: A 33-year-old previously healthy woman presented with fluctuating dysphagia and a sensation of a pharyngeal foreign body, exhibiting diurnal variation characterized by improvement in the morning and worsening in the evening. Symptom onset coincided with a family quarrel and subsequently intensified after an upper respiratory tract infection. Multiple laryngoscopies, gastrointestinal endoscopies, and brain magnetic resonance imaging (MRI) revealed no abnormalities. Initially misdiagnosed with an anxiety-depressive disorder, she experienced only partial and transient improvement with citalopram. Two subsequent acute exacerbations triggered by infections led to a complete inability to swallow. Neurological examination indicated dysarthria, choking when drinking, and mild distal limb weakness, assessed at 4+/5 on the Medical Research Council scale. The neostigmine test yielded a strong positive result, and serum anti-acetylcholine receptor (AChR) antibodies were detected at a titer of 1:10, while repetitive nerve stimulation (RNS) remained normal. Chest computed tomography (CT) revealed no thymoma. The patient was diagnosed with moderate generalized MG characterized by AChR-antibody positivity and classified as MGFA class IIIb. Following the failure of initial immunosuppressive therapy, which included prednisone at 30 mg daily, pyridostigmine at 60 mg three times daily, and azathioprine at 25 mg daily, the patient underwent two cycles (totaling 8 infusions) of the FcRn antagonist efgartigimod. Marked improvement in dysphagia was observed, as evidenced by a decrease in the MG-Activities of Daily Living (MG-ADL) score from 8 to 2 and a reduction in the Quantitative Myasthenia Gravis (QMG) score from 10 to 1. At the 6-month follow-up, the patient achieved complete clinical remission, with both MG-ADL and QMG scores reaching 0, and attained minimal manifestation status, while prednisone was tapered to 5 mg daily. Conclusion: This case indicates that isolated fluctuating dysphagia warrants consideration of MG, even in the presence of psychosocial stressors or partial response to psychiatric medications. A negative RNS does not exclude MG, especially in bulbar-onset cases. Clinicians should prioritize organic etiologies and perform neostigmine and anti-AChR testing to avoid delayed diagnosis. Furthermore, efgartigimod is effective for refractory bulbar MG, enabling rapid remission and corticosteroid tapering.