一例高龄患者的极晚发型重症肌无力：诊断挑战与早期识别的重要性

文献信息

中文摘要

背景： 重症肌无力是一种神经肌肉接头自身免疫性疾病，以波动性骨骼肌无力为特征。晚发型MG（发病年龄≥50岁且<65岁）和极晚发型MG（VLOMG；发病年龄≥65岁）是日益被认识到的亚组，而高龄患者的诊断仍然具有挑战性，因为症状常与年龄相关疾病和合并症重叠。病例介绍：一名88岁男性极晚发型重症肌无力患者（症状约在85岁时出现），因数日来迅速加重的吞咽困难和构音障碍急诊转诊，这些症状叠加在此前三年内逐渐加重的波动性复视、吞咽困难、构音障碍和易疲劳性延髓症状之上。由于高龄、既往腔隙性脑梗死以及多种合并症，包括肺血栓栓塞、慢性肾脏病和永久性心脏起搏器植入（后者使脑MRI无法进行），初始诊断评估具有挑战性。神经系统检查及症状的特征性波动提示重症肌无力。血清学检测证实乙酰胆碱受体抗体显著升高，而MuSK抗体阴性。鉴于高抗体滴度和明确的临床表现，未进行重复神经刺激。胸部计算机断层扫描排除了胸腺瘤。使用吡斯的明、硫唑嘌呤（因慢性肾脏病IIIB期，维持剂量低于标准）和低剂量泼尼松（因年龄和合并症情况而选择）治疗，在八周随访中患者报告早期临床改善（言语和吞咽约60%）；经过验证的严重程度量表（MG-ADL）评分为六分（评分范围0-24）。结论：对于表现为波动性眼部和延髓症状的高龄患者，即使存在可能掩盖诊断的多种合并症，重症肌无力仍应作为重要的鉴别诊断。在该患者中，早期识别、抗体检测和个体化启动治疗带来了有意义的短期改善；但单例病例八周随访不能确定此类治疗可预防疾病进展或肌无力危象，需要更长时间随访和更多病例。

英文摘要

Background: Myasthenia gravis is an autoimmune disorder of the neuromuscular junction characterized by fluctuating skeletal muscle weakness. Late-onset MG (onset ≥ 50 and <65 years) and very late-onset MG (VLOMG; onset ≥ 65 years) are increasingly recognized subgroups, and diagnosis in very elderly patients remains challenging because symptoms frequently overlap with age-related conditions and comorbidities. Case Presentation: An 88-year-old man with very late-onset myasthenia gravis (symptom onset at approximately age 85) was urgently referred because of a several-day history of rapidly worsening dysphagia and dysarthria, superimposed on fluctuating diplopia, dysphagia, dysarthria, and fatigable bulbar symptoms that had progressively worsened over the preceding three years. Initial diagnostic evaluation was challenging because of advanced age, previous lacunar infarctions, and multiple comorbidities, including pulmonary thromboembolism, chronic kidney disease, and permanent pacemaker implantation (which precluded brain MRI). Neurological examination and the characteristic fluctuation of symptoms raised suspicion of myasthenia gravis. Serological testing confirmed markedly elevated acetylcholine receptor antibodies, whereas MuSK antibodies were negative. Repetitive nerve stimulation was not performed given the high antibody titer and unambiguous clinical presentation. Thoracic computed tomography excluded thymoma. Treatment with pyridostigmine, azathioprine (maintenance dose kept lower than standard due to chronic kidney disease stage IIIB), and low-dose prednisone (selected due to age and comorbidity profile) resulted in early, patient-reported clinical improvement (approximately 60% in speech and swallowing) over eight weeks of follow-up; a validated severity scale (MG-ADL) showed a score of six (scoring range 0-24). Conclusions: Myasthenia gravis should remain an important differential diagnosis in very elderly patients presenting with fluctuating ocular and bulbar symptoms, even in the presence of multiple comorbidities that may obscure the diagnosis. In this patient, early recognition, antibody testing, and individualised initiation of therapy were followed by meaningful short-term improvement; a single case with eight weeks of follow-up cannot establish that such therapy prevents disease progression or myasthenic crisis, and longer follow-up and additional cases are needed.