甲基丙二酸尿症合并同型半胱氨酸血症可以导致多系统损伤,以中枢神经损伤为主,周围神经损伤较少见.本文拟就1例以周围神经损伤为主要表现的甲基丙二酸尿症合并同型半胱氨酸血症患者进行研究.患儿为10岁男童,主因“双下肢无力1个月”就诊,既往轻度智力运动发育落后,轻度学习困难.3岁时曾有蛋白尿,经治疗后好转.8岁6个月时曾有抽搐,应用丙戊酸钠治疗后发作控制.体格检查显示双侧膝腱反射减弱,双侧跟腱反射未引出,浅深感觉未见异常,双侧巴氏征(+),肌电图检查证实为周围神经损伤.尿液甲基丙二酸及血清同型半胱氨酸显著升高,符合甲基丙二酸尿症合并同型半胱氨酸血症诊断,MMACHC基因分析显示患者存在两个致病杂合突变(c.365A＞T和c.609G ＞A),证实为cblC缺陷.针对原发病,给予维生素B12、亚叶酸钙、左卡尼汀及甜菜碱治疗,患者病情逐步改善,半年后随访患儿无力症状消失,运动功能恢复,智力发育亦显著进步,可正常就读.本例患者提示,周围神经损伤也是甲基丙二酸尿症合并同型半胱氨酸血症的合并症之一,对不明原因周围神经疾病,尤其是伴有多系统受累的患者,应尽早行尿液有机酸分析及血清总同型半胱氨酸测定,以明确诊断,正确治疗,改善预后.%Methylmalonic aciduria combined homocysteinemia can cause multisystemic damages, mainly involving central nervous system, while the peripheral nerves are rarely impaired. A 10-year-old boy complained of weakness of both lower extremities for 1 month. His past history showed mildly delay of intelligence as well as motor development. He had proteinuria when he was 3 years old and was diagnosed as epilepsy, which was controlled by sodium valproate when he was 8 years 6 months old. His physical examination showed attenuated bilateral knee jerk reflex, while the bilateral achilles tendon reflex was absent ; the examination of sensation was normal and the bilateral Babinski sign was positive. The electro-myography indicated injury of peripheral nerves. The elevated levels of urine methylmalonic aciduria and plasma homocysteinemia were consistent with the diagnosis of methylmalonic aciduria combined homocysteinemia. The pathogenic gene was confirmed as MMACHC, on which two pathogenic mutations (c. 365A >T and c. 609G > A) were detected. cblC defect was confirmed. He was treated by vitamin B12, calcium folinate, L-carnitine and betaine supplementation, and significant improvement was observed after 6 months. According to this case, we suggest that urinary organic acid analysis and plasma homocysteine should be performed in patients with unknown peripheral neuropathy, especially combined with multisystemic damages. Early diagnosis and treatment are important to improve the prognosis.
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