球形细胞脑白质营养不良的临床特点及基因突变分析

The clinical features and molecular genetic assay of globoid cell leukodystrophy(Krabbe disease)

目的探讨球形细胞脑白质营养不良（Krabbe病）患儿的临床、影像学和酶学特点及GALC基因突变特征。方法采用荧光底物法检测外周血白细胞β-半乳糖脑苷脂酶（GALC）活性,回顾分析2010年6月至2012年12月广州市妇女儿童医疗中心来自不同家系的3例Krabbe病患儿的临床、影像学特点。应用RT-PCR及直接测序法进行GALC基因突变分析。结果 3例Krabbe病患儿,其中男2例,女1例,年龄3个月至40个月,临床分型婴儿型1例,晚发婴儿型2例。因＂哭闹、抽搐或精神运动发育倒退等＂就诊,头颅MRI提示双侧内囊后肢或脑白质对称性异常信号影,磁共振波普成像（MRS）提示N-乙酰天门冬氨酸/肌酐（NAA/Cr）比值下降,胆碱/肌酐（Cho/Cr）比值升高。外周血白细胞GALC酶活性0～0.2 nmol/（mg·17 h）[正常参考范围18～75 nmol/（mg·17 h）]。GALC基因突变分析发现2个已知致病突变p.S68F、p.R531H,3个新错义突变p.D46Y、p.G59S、p.P154H。随访18个月,死亡2例,病情进行性加重1例。结论 Krabbe病患儿主要临床表现为激惹、抽搐、精神运动发育迟缓或倒退。起病越早,进展越快。头颅MRI表现双侧对称性脑白质或内囊后肢异常信号应高度怀疑Krabbe病,白细胞GALC酶活性测定及GALC基因突变分析有助确诊。

Objective To explore the clinical, radiological and emzymic features and gene mutation features of GALC gene in children with Krabbe disease.MethodsThe clinical, radiological and emzymic features of 3 unrelated childrenwith Krabbe disease in the Guangzhou Women and Children＇s Medical Centre from Jun.2010 to Dec.2012 were retrospectively reviewed. The galactocerebrosidase activity in leukocytes was detected by fluorescent substrate method. Themutation analysis of GALC gene was performed by RTPCR and direct sequencing.ResultsThree index cases were diagnosed at ages ranging from 3～40 months after birth. They were 1 female with infantile form and 2 male with lateinfantile form. They were admitted to our hospital for crying,irritation, convulsion, psychomotor retardation or regression.Brain MRI showed symmetric signal changes in the posterior limb of the internal capsule and the periventricular whitematter. MRS revealed a reduction of total Nacetylaspartate（neuroaxonal marker）as well as strongly elevated inositol（glial marker）in white matter and the posterior limb of the internal capsule. The galactocerebrosidase activities of the 3patients were remarkably low,ranging from 0～0.2 nmol/（mg·17 h）protein（normal range 18～75）. Five different mutations were identified, three（p.D46Y,p.G59S and p.P154H）of which were novel in the GALC gene. Followed up for 18months,2 cases died and one became more serious progressively.ConclusionThe clinical features of Krabbe diseaseare irritability,convulsion,psychomotor retardation or regression. The earlier the onset,the faster the progress. It shouldbe highly suspected when brain MRI shows symmetric white matter changes. The test of galactocerebrosidase activity and the molecular genetic assay of GALC gene can confirm the definite diagnosis of Krabbe disease.