Abstract:

Objective To study histological features, immunophenotype, genotype, diagnosis and differential diagnosis, treatment and prognosis of one case of mitochondrial encephalomyopathy with lactic acidemia and stroke-like episodes (MELAS), and to summarize the clinicopathological features and key points of diagnosis and differential diagnosis. Methods and Results A 55-year-old female presented language disorder with memory disorders for 2 months, and her head MRI showed space-occupying lesion of left temporal lobe. An exploratory craniotomy was performed. Histological morphology showed patchy grey and white matter structure, scattered hemorrhagic necrosis, small vascular hyperplasia, luminal hyperemia and vasodilatation, and scattered lymphocytic infiltration. By using immunohistochemical staining, the membrane of lymphocytes was focally positive for CD3 and CD20, and neurons were positive for neuronal nuclei (NeuN). Periodic acid-Schiff (PAS) staining was focally positive. In further musc le biopsy, modified Gomori trichrome (MGT) staining showed a lot of scattered ragged-red fibers (RRF), suggesting myopathologic change of mitochondrial encephalomyopathy. A m.3243A > G mutation (about 9%) was found in the direct sequencing genetic testing. The final diagnosis was MELAS. After operation, the patient received antiepileptic, hypoglycemic and neurotrophic treatment. Conclusions Adult-onset MELAS is a rare disease with various clinical manifestations. A definite diagnosis depends on clinical manifestations, histopathological characteristics, immunophenotype and genetic testing.

Key words: MELAS syndrome, Immunohistochemistry, Pathology

摘要：

目的 报道 1 例线粒体脑肌病伴高乳酸血症和卒中样发作（MELAS）患者的组织学形态、免疫表型、基因型、诊断与鉴别诊断、治疗与预后，总结其临床病理学特征及诊断与鉴别诊断要点。方法与结果 女性患者，55 岁，临床表现为语言表达障碍伴记忆障碍 2 月余；头部 MRI 显示左侧颞叶占位性病变；遂行开颅病变组织活检术。组织学形态观察，片状灰白质结构，散在出血性坏死，部分区域小血管明显增生，管腔扩张、充血，散在淋巴细胞浸润；免疫组织化学染色，淋巴细胞胞膜散在表达 CD3 和CD20，神经元表达神经元核抗原；高碘酸-雪夫染色呈散在阳性；进一步行肌肉组织活检术，改良 Gomori三色染色可见较多散在破碎红纤维，考虑线粒体脑肌病肌肉病理改变。线粒体相关基因检测存在m.3243A > G 突变（约 9%），为致病性突变。最终明确诊断为 MELAS。术后予以抗癫 、降糖和营养神经治疗。结论 MELAS 临床少见，临床表现多样，明确诊断依靠临床表现、组织学形态、免疫表型和基因检测。

关键词: MELAS综合征, 免疫组织化学, 病理学