目的：报告良性单侧下肢肌萎缩（BMALL）1例，并结合文献探讨该病的病因及发病机制、临床表现、 辅助检查、诊断依据及预后等。方法：回顾性分析该患者的临床资料，检索国内外相关文献，总结分析。结 果：患者4年前无明显诱因出现右下肢肌萎缩，以腓肠肌萎缩为主，逐渐向上进展，肌无力相对较轻，无感觉 异常、锥体束征及延髓损害。查体右下肢肌张力正常，肌力5—级，腱反射（-），无肌束颤动，病理征（-）。肌肉 磁共振显示右下肢腓肠肌、比目鱼肌、胫前肌、股四头肌及臀大肌都有不同程度萎缩，肌电图示右下肢神经 源性损害，右股四头肌肌肉活检提示神经源性肌萎缩。搜索既往报道的BMALL患者95例，男性患者明显 多于女性，所有患者均无明显肌无力症状，极少部分有轻度感觉异常。所有患者肌电图均提示神经源性损 害，肌肉活检者均提示神经源性肌萎缩。大部分患者随访数年预后良好。结论：BMALL是一种相对良性的 神经肌肉疾病，临床表现为单侧下肢萎缩，肌肉萎缩与肌无力不成比例，症状起病隐袭，进展缓慢，不影响日 常生活。目前病因及发病机制尚不明确，诊断主要依赖病史、体格检查、肌肉磁共振、肌电图、肌肉活检等， 目前尚无特效治疗，一般良性进展，但也有少数预后不佳的病例。

To report a case of benign monomelic amyotrophy of lower limb (BMALL), and to explore the etiology, pathogenesis, clinical manifestations, auxiliary examination, diagnosis and prognosis of the disease in accordance with the literature. Methods: The clinical data of this patient were analyzed retrospectively. The related domestic and foreign literatures were retrieved and analyzed. Results: Four years ago, the patient found muscle atrophy of his right lower limb with no obvious incentive, gastrocnemius involved mainly. Muscle atrophy gradually progressed upward. Compared with muscle atrophy, muscle weakness was relatively mild. There were no paresthesia, pyramidal signs and medullary damage. Physical examination showed normal right leg muscle tension, muscle strength 5— grade, tendon reflexes (-), no fasciculation fibrillation, pathological sign (-). Muscle MRI showed right lower extremity gastrocnemius, soleus muscle, anterior tibialis, quadriceps and gluteus maximus have varying degrees of atrophy. EMG showed right lower extremity neurogenic damage. Right quadriceps muscle biopsy showed neurogenic muscular atrophy. In previously reported 95 cases of BMALL patients, more patients were male, all patients had no symptoms of muscle weakness, and a small part had mild sensory abnormalities. Electromyograms of all patients showed neurogenic damage, and muscle biopsy all showed neurogenic muscle atrophy. Most patients have a good prognosis after several years of follow-up. Conclusion: BMALL is a relatively benign neuromuscular disease. The clinical manifestations are unilateral lower limb atrophy, muscular atrophy and myasthenia gravis disproportionately. The onset of symptoms is insidious and the progression is slow without affecting daily life. The etiology and pathogenesis are not clear currently. The diagnosis depends mainly on medical history, physical examination, muscle magnetic resonance, electromyography and muscle biopsy. There is no specific treatment. Generally, BMALL has benign progress, but there are a few cases of poor prognosis.