Abstract: Background   The main clinical manifestations of mitochondrial myopathy are chronic limb weakness and muscular soreness. Subclinical peripheral nerve injury is also reported, but acute axonal neuropathy.like syndrome concurrent with lactic acidosis is rare. In this paper the clinical features of 2 patients presenting as acute lactic acidosis and sudden muscle weakness were analyzed. Pathological changes and genetic mutations were detected.  Methods Electromyography (EMG) and muscle biopsy were performed. Modified Gomori trichrome (MGT) and succinodehydrogenase (SDH) staining were used to identify pathological changes. Changes of ultra microstructure of muscular tissue were observed under electron microscope. Mitochondrial DNA (mtDNA) full length sequencing was performed using 24 pairs of partially overlapping primers.  Results  EMG showed a coexistence of neurogenic and myogenic changes. Dramatic decrease of motor nerve amplitude and moderately reduced sensory nerve amplitude were observed but nerve conduction velocity was normal in both patients. Impressive ragged red fibers were seen on MGT staining. Electron microscope showed dramatic mitochondrial abnormalities in Case 1 and paracrystaline inclusions in Case 2. mtDNA sequencing showed 3243A > G mutation in Case 1 and 8344A > G mutation in Case 2. Conclusions Mitochondrial myopathy can present as metabolic crisis like acute lactic acidosis, dyspnea and acute motor axonal neuropathy.like syndrome. It is a life.threatening phenotype that needs more attention.

Key words: Mitochondrial myopathies, Peripheral nervous system diseases, Acidosis, lactic, Pathology, Genes, Mutation

摘要： 研究背景   线粒体肌病主要表现为慢性四肢近端肌无力伴肌肉酸痛，可合并亚临床周围神经损害，而急性轴索性运动感觉神经病样表现伴乳酸酸中毒极为罕见。本研究对2 例急性轴索性运动感觉神经病样表现伴乳酸中毒患者的临床特点进行分析，探索其病理和基因突变特点。方法 通过周围神经和肌肉肌电图检查，分析神经损害特点；改良Gomori 三色、琥珀酸脱氢酶等肌肉组织酶学染色明确肌肉病变性质；电子显微镜观察肌肉组织超微结构改变；24 对重叠引物测序法行线粒体基因全序列测定。结果 肌电图提示神经源性和肌源性损害并存，运动神经波幅显著降低、传导速度正常，感觉神经波幅轻至中度降低、传导速度正常。病理检查呈慢性肌肉病改变，改良Gomori 三色染色可见较多破碎红纤维；电子显微镜观察线粒体数目和形态显著异常，并可见典型的“结晶”样包涵体。线粒体基因全序列测定明确为3243A > G（例1）和8344A > G（例2）位点突变，均为已知致病突变。结论 线粒体肌病可以表现为急性轴索性运动感觉神经病样表现和代谢危象，为急症型，值得重视。

关键词: 线粒体肌病, 周围神经系统疾病, 酸中毒, 乳酸性, 病理学, 基因, 突变