脂肪酸羥化酶相關(guān)性神經(jīng)變性病四例臨床表型及基因突變分析

黃嘯君 劉曉黎 王田 沈雋逸 陳生弟 唐維國(guó) 曹立

脂肪酸羥化酶相關(guān)性神經(jīng)變性病四例臨床表型及基因突變分析

黃嘯君 劉曉黎 王田 沈雋逸 陳生弟 唐維國(guó) 曹立

目的報(bào)道4例脂肪酸羥化酶相關(guān)性神經(jīng)變性病患者,并復(fù)習(xí)相關(guān)文獻(xiàn),總結(jié)該病臨床表型和基因突變特點(diǎn).方法收集4例脂肪酸羥化酶相關(guān)性神經(jīng)變性病患者臨床資料和家系資料,標(biāo)準(zhǔn)酚氯仿法提取患者及其父母基因組DNA并行Sanger測(cè)序.結(jié)果4例患者中3例(例2、例3和例4)具有典型脂肪酸羥化酶相關(guān)性神經(jīng)變性病表現(xiàn),1例(例1)表現(xiàn)為非典型.FA2H基因檢測(cè)顯示,4例患者均存在FA2H基因突變,其中例1為復(fù)合雜合突變c.461G>A(p.Arg154His)和c.794T>G(p.Phe265Cys);例2僅發(fā)現(xiàn)1種已報(bào)道的雜合突變c.703C>T(p.Arg235Cys),進(jìn)一步對(duì)例2及其母進(jìn)行單核苷酸多態(tài)性檢測(cè),亦未發(fā)現(xiàn)缺失突變;例3為雜合突變c.688G>A(p.Glu230Lys)和插入突變c.172_173insGGGCCAGGAC(p.Ile58ArgfsX47);例4為復(fù)合雜合突變c.688G>A(p.Glu230Lys)、c.968C>A(p.Pro323Gln)和c.976G>A(p.Gly326Asp),其父為c.688G>A(p.Glu230Lys)突變攜帶者,其母為c.968C>A(p.Pro323Gln)和c.976G>A(p.Gly326Asp)突變攜帶者.根據(jù)美國(guó)醫(yī)學(xué)遺傳學(xué)和基因組學(xué)會(huì)標(biāo)準(zhǔn),例1的FA2H基因雜合突變c.461G>A(p.Arg154His)為"可能致病"、c.794T>G(p.Phe265Cys)為"可能致病";例2的FA2H基因雜合突變c.703C>T(p.Arg235Cys)為"可能致病";例3的FA2H基因雜合突變c.688G>A(p.Glu230Lys)為"致病"、插入突變c.172_173insGGGCCAGGAC(p.Ile58ArgfsX47)為"致病";例4的FA2H基因雜合突變c.688G>A(p.Glu230Lys)為"致病"、c.968C>A(p.Pro323Gln)為"致病"、c.976G>A(p.Gly326Asp)為"可能致病".結(jié)論脂肪酸羥化酶相關(guān)性神經(jīng)變性病具有高度臨床和遺傳異質(zhì)性,痙攣性截癱是最主要的臨床表現(xiàn),對(duì)于復(fù)雜型常染色體隱性遺傳性遺傳性痙攣性截癱,尤其合并構(gòu)音障礙、智力減退、腦白質(zhì)病變和小腦萎縮等臨床特征的患者,應(yīng)考慮FA2H基因突變導(dǎo)致的脂肪酸羥化酶相關(guān)性神經(jīng)變性病.

神經(jīng)變性疾病; 脂肪酸類; 混合功能氧化酶類; 表型; 基因; 突變

FA2H基因突變與腦白質(zhì)營(yíng)養(yǎng)不良、遺傳性痙攣性截癱35型(SPG35型)和腦組織鐵沉積性神經(jīng)變性病(NBIA)均相關(guān)[1?3].該基因突變導(dǎo)致的腦組織鐵沉積性神經(jīng)變性病亞型占所有腦組織鐵沉積性神經(jīng)變性病的比例較低(<1%),臨床表現(xiàn)具有一定特異性,典型表現(xiàn)為痙攣性截癱、小腦共濟(jì)失調(diào)、認(rèn)知功能障礙、癲發(fā)作等.FA2H基因突變導(dǎo)致的臨床表型存在相互重疊,故將上述3種臨床表型統(tǒng)稱為脂肪酸羥化酶相關(guān)性神經(jīng)變性病[FAHN,在線人類孟德爾遺傳數(shù)據(jù)庫(OMIM)編號(hào):611026][1].本研究報(bào)道4例脂肪酸羥化酶相關(guān)性神經(jīng)變性病患者,并復(fù)習(xí)相關(guān)文獻(xiàn),總結(jié)該病臨床表型和基因突變特點(diǎn).

對(duì)象與方法

一、研究對(duì)象

研究對(duì)象均來自2012年1月-2017年1月上海交通大學(xué)醫(yī)學(xué)院附屬瑞金醫(yī)院神經(jīng)科擬診脂肪酸羥化酶相關(guān)性神經(jīng)變性病患者,診斷依據(jù)臨床表型,其中表現(xiàn)為痙攣性截癱表型的患者,參照Harding診斷標(biāo)準(zhǔn)[4];共4例,男性3例,女性1例;年齡5～50歲,平均28歲.以及4例患者父母共7例(例2父親已死亡),男性3例,女性4例;年齡30～78歲,平均56.14歲;均無相似臨床癥狀,否認(rèn)近親婚配.本研究經(jīng)上海交通大學(xué)醫(yī)學(xué)院附屬瑞金醫(yī)院道德倫理委員會(huì)審核批準(zhǔn),所有患者及其家屬均知情同意并簽署知情同意書.

二、研究方法

1.一般資料收集 采集4例患者的家系資料、臨床病史,以及神經(jīng)系統(tǒng)查體、影像學(xué)檢查等.

2.標(biāo)本收集與基因組DNA提取 采集4例患者及其父母外周靜脈血各5 ml,予乙二胺四乙酸(EDTA)抗凝管(美國(guó)BD公司)抗凝.采用標(biāo)準(zhǔn)酚氯仿法提取患者及其父母基因組DNA,紫外分光光度計(jì)(美國(guó)Bio?Rad公司)于260和280 nm波長(zhǎng)處定量測(cè)定基因組DNA.

圖1 例1頭部MRI檢查所見 1a 橫斷面FLAIR成像顯示,雙側(cè)側(cè)腦室旁稍高信號(hào)影(箭頭所示),提示腦白質(zhì)病變1b 橫斷面T2WI顯示,雙側(cè)基底節(jié)區(qū)鐵離子沉積(箭頭所示)1c 橫斷面 T2WI顯示,小腦腦溝輕度增寬(箭頭所示)Figure 1 Head MRI findings in Case 1 Axial FLAIR showed bilateral paraceles high?intensity signal,suggesting lesion in white matter of the brain(arrow indicates,Panel 1a).Axial T2WI reveald ferrum deposit in bilateral basal ganglia regions(arrows indicate,Panel 1b).Axia T2WI indicated cerebellar sulus slightly broaden(arrow indicates,Panel 1c).

3.Sanger測(cè)序 (1)聚合酶鏈反應(yīng)(PCR):根據(jù)FA2H基因外顯子進(jìn)行PCR擴(kuò)增,參照FA2H基因第1～7外顯子及其側(cè)翼序列設(shè)計(jì)引物,由英濰捷基(上海)貿(mào)易有限公司合成,正向引物序列為FA2H?1F:5'?GGTATGCAAATGAGCAGGTG?3'、FA2H?2F:5'?CTTGACCTCCCAAAGTGCTG ?3'、FA2H ?3F:5'?CCTGCCGATTTAGCACCTC ?3'、FA2H ?4F:5'?GGCTGAGGCAGAAGAGTCAC ?3'、FA2H ?5F:5'?AAGGACCCCAGCAGTATGG ?3'、FA2H ?6F:5'?ACCAAAGGTGCCAAGCCTAC ?3'、FA2H ?7F:5'?GCTGGGGACAATAAAAGACAC?3',反向引物序列為 FA2H?1R:5'?GAGAGAGGAAGGAGGGGTTG?3'、FA2H ?2R:5'?TGGACACCTGCTTCTCCTTC ?3'、FA2H?3R:5'?ATGTTCCTCCCTCCCTGAC?3'、FA2H?4R:5'?TTTCTGCTGATGTGTTGTTGG?3'、FA2H?5R:5'?AAAGGTGATGCGTAAACAAGG?3'、FA2H?6R:5'?GTCTGCACCAGGGAAAGAG ?3'、FA2H ?7R:5'?TGGATGTGACCCTCCTACC?3'.PCR反應(yīng)體系共25 μl,依次加入 dNTPs 2.50 mmol、2XGC 緩沖液Ⅰ12.50 μl、各引物序列 5 pmol、模板 DNA 100 ng以及r?Taq 1 U,再加水補(bǔ)充至25 μl;反應(yīng)條件為 95 ℃預(yù)變性5 min,95℃ 90 s、62 ℃ 1 min、72℃ 2 min,共循環(huán)35次,72℃延伸10 min.(2)Sanger測(cè)序:PCR擴(kuò)增產(chǎn)物采用DNAStar軟件包中SeqMan軟件(美國(guó)DNAStar公司)進(jìn)行比對(duì).例2及其母(其父已死亡,未能采集標(biāo)本)基因組DNA采用Illumina Human Ommi Zhonghua?8 Bead Chips全基因組分型芯片(美國(guó)Illumina公司)進(jìn)行單核苷酸多態(tài)性(SNP)檢測(cè).對(duì)檢出的FA2H基因突變,根據(jù)美國(guó)醫(yī)學(xué)遺傳學(xué)和基因組學(xué)會(huì)(ACMG)標(biāo)準(zhǔn)[5]進(jìn)行致病性判定.

結(jié) 果

4例患者臨床表現(xiàn)符合脂肪酸羥化酶相關(guān)性神經(jīng)變性病,經(jīng)基因檢測(cè)確定存在FA2H基因突變.

一、臨床特征

例1男性,50歲,因進(jìn)行性行走困難16年,于2014年6月5日至我院神經(jīng)科門診就診.患者16年前(34歲時(shí))無明顯誘因開始出現(xiàn)行走不穩(wěn),逐漸進(jìn)展為雙下肢乏力,伴僵硬感,進(jìn)行性加重,同時(shí)伴言語欠流利,但無明顯飲水嗆咳,上肢活動(dòng)自如,精細(xì)動(dòng)作尚可準(zhǔn)確完成,無肢體抽搐、記憶力減退;3年前開始出現(xiàn)排尿控制障礙.患者生長(zhǎng)發(fā)育里程碑與同齡正常人無明顯差異,智力發(fā)育可.父母無相似臨床癥狀或其他神經(jīng)系統(tǒng)疾病,否認(rèn)近親婚配.門診神經(jīng)系統(tǒng)檢查:神志清楚,語言欠流利;雙側(cè)瞳孔等大、等圓,直徑約3 mm,對(duì)光反射靈敏;雙側(cè)鼻唇溝對(duì)稱,伸舌居中;雙下肢髂腰肌肌力4+級(jí)、股四頭肌5級(jí)、脛前肌5級(jí)、腓腸肌5級(jí),雙側(cè)外展肌肌力4+級(jí)、內(nèi)收肌5級(jí),雙下肢肌張力略增高;剪刀步態(tài);雙側(cè)快復(fù)輪替動(dòng)作笨拙,指鼻試驗(yàn)和跟?膝?脛試驗(yàn)尚可,Romberg征陽性;雙上肢腱反射正常、雙下肢膝反射和踝反射增強(qiáng)、雙側(cè)踝陣攣減弱,雙側(cè)病理征陽性.影像學(xué)檢查:頭部MRI顯示輕度小腦萎縮,胼胝體無明顯萎縮,雙側(cè)側(cè)腦室角白質(zhì)變性,雙側(cè)基底節(jié)區(qū)鐵離子沉積(圖1).

例2女性,22歲,因進(jìn)行性行走困難19年,發(fā)作性意識(shí)喪失伴肢體抽搐3年,于2012年9月5日至我院神經(jīng)科門診就診.患者19年前(3歲時(shí))開始出現(xiàn)行走困難,伴下肢僵硬感,進(jìn)行性加重,隨后出現(xiàn)智力減退;小學(xué)3年級(jí)(10歲)時(shí)輟學(xué),隨后逐漸出現(xiàn)雙手動(dòng)作笨拙、言語模糊,但無吞咽困難和飲水嗆咳;19歲時(shí)出現(xiàn)癲發(fā)作,一直服用丙戊酸鈉至今;目前已喪失獨(dú)立行走能力,大小便控制障礙.患者出生至學(xué)齡前生長(zhǎng)發(fā)育無明顯異常.父母無相似臨床癥狀或其他神經(jīng)系統(tǒng)疾病,否認(rèn)近親婚配.門診神經(jīng)系統(tǒng)檢查:神志清楚,語言欠流利;雙側(cè)瞳孔等大、等圓,直徑約3 mm,對(duì)光反射靈敏;雙側(cè)鼻唇溝對(duì)稱,伸舌居中;雙上肢肌力5級(jí)、雙下肢3-級(jí),四肢肌張力增高;雙側(cè)快復(fù)輪替動(dòng)作笨拙,步態(tài)檢查不能完成;雙上肢腱反射增強(qiáng)、雙下肢膝反射強(qiáng)陽性和踝反射增強(qiáng)、踝陣攣減弱,雙側(cè)病理征陽性.頭部MRI顯示腦白質(zhì)病變.

例3男性,5歲,主因進(jìn)行性行走困難2年,于2016年4月13日至我院神經(jīng)科門診就診.患兒2年前(3歲時(shí))開始出現(xiàn)行走困難,行走時(shí)雙腿內(nèi)收,進(jìn)行性加重,伴語速減慢,雙上肢無明顯活動(dòng)異常.患兒生長(zhǎng)發(fā)育與同齡正常兒童無明顯差異,智力發(fā)育可.父母無相似癥狀或其他神經(jīng)系統(tǒng)疾病,否認(rèn)近親婚配.門診神經(jīng)系統(tǒng)檢查:神志清楚,語速緩慢;雙側(cè)瞳孔等大、等圓,直徑約3 mm,對(duì)光反射靈敏;雙側(cè)鼻唇溝對(duì)稱,伸舌居中;雙上肢肌力5級(jí)、雙下肢4級(jí),雙下肢內(nèi)收肌力5級(jí)、外展肌力3級(jí),四肢肌張力增高;呈剪刀步態(tài);雙側(cè)指鼻試驗(yàn)尚可,Romberg征陰性;雙上肢腱反射正常,雙下肢膝反射和踝反射增強(qiáng)、雙側(cè)踝陣攣減弱,雙側(cè)病理征陽性.頭部MRI顯示雙側(cè)側(cè)腦室后角旁腦白質(zhì)病變,小腦延髓池輕度增寬.

例4男性,35歲,主因進(jìn)行性行走困難31年,發(fā)聲困難、飲水嗆咳19年,發(fā)作性意識(shí)喪失伴肢體抽搐10年,于2012年6月15日至我院神經(jīng)科門診就診.患者31年前(4歲時(shí))出現(xiàn)雙側(cè)足背屈困難,行走時(shí)足尖著地,長(zhǎng)時(shí)間行走后雙側(cè)膝關(guān)節(jié)疼痛,進(jìn)行性加重;5歲時(shí)出現(xiàn)行走困難,伴左足不自主內(nèi)翻,進(jìn)行性加重;6歲時(shí)出現(xiàn)握筆姿勢(shì)異常,表現(xiàn)為內(nèi)旋,書寫尚工整;8歲(小學(xué)1年級(jí))時(shí)學(xué)習(xí)成績(jī)尚可,但發(fā)聲低、書寫慢;9歲(小學(xué)2年級(jí)下半學(xué)期,留級(jí)1年)學(xué)習(xí)成績(jī)落后,行走姿勢(shì)異常進(jìn)一步加重,雙側(cè)膝關(guān)節(jié)不能彎曲;12歲(小學(xué)5年級(jí)時(shí))右足不自主內(nèi)翻,不能獨(dú)立行走,行矯形術(shù);小學(xué)畢業(yè)后輟學(xué);16歲時(shí)不能行走并出現(xiàn)發(fā)聲困難、飲水嗆咳;20歲時(shí)雙手呈握拳姿勢(shì),語速明顯減慢,需使用輪椅;25歲時(shí)曾出現(xiàn)一次午睡后一側(cè)肢體和口角不自主抽搐,眼球向同側(cè)凝視伴意識(shí)喪失,持續(xù)5 min后好轉(zhuǎn),此后反復(fù)出現(xiàn)類似發(fā)作,持續(xù)30 min以上,服用丙戊酸鈉后癥狀控制欠佳,進(jìn)行性加重,逐漸出現(xiàn)言語困難,只能講單字,保持坐位困難,大小便失禁;28歲時(shí)完全不能言語,僅能點(diǎn)頭示意,此后逐漸出現(xiàn)頭頸部無力,頭向后仰或偏向左側(cè),僅能眨眼示意;30歲時(shí)反應(yīng)遲鈍,呼之反應(yīng)差;32歲后抽搐發(fā)作逐漸減少,自行停用丙戊酸鈉,家人訴其肢體僵硬感較前略有好轉(zhuǎn).患者父母無相似癥狀或其他神經(jīng)系統(tǒng)疾病,否認(rèn)近親婚配;其妹5歲時(shí)開始出現(xiàn)相似臨床癥狀.門診體格檢查:神志清楚,言語不能,反應(yīng)遲鈍,計(jì)算力和定向力差;雙側(cè)瞳孔等大、等圓,直徑約為4 mm,直接和間接對(duì)光反應(yīng)靈敏,余腦神經(jīng)檢查不配合;四肢肌肉極度萎縮,肌力0級(jí),雙上肢關(guān)節(jié)屈曲攣縮,雙下肢肌張力降低;行走不能;四肢腱反射未引出,雙側(cè)病理征陰性.頭部MRI顯示,大腦皮質(zhì)、胼胝體和小腦萎縮,伴腦白質(zhì)營(yíng)養(yǎng)不良和基底節(jié)區(qū)T2WI低信號(hào).

二、基因檢測(cè)

FA2H基因檢測(cè)顯示,4例患者均存在FA2H基因突變,例1為復(fù)合雜合突變c.461G>A(p.Arg154His)和c.794T>G(p.Phe265Cys,圖2),此2種突變?cè)诩蚁抵谐霈F(xiàn)共分離現(xiàn)象;例2僅發(fā)現(xiàn)1種已報(bào)道的雜合突變c.703C>T(p.Arg235Cys,圖3),其母未攜帶該突變,進(jìn)一步對(duì)例2及其母進(jìn)行單核苷酸多態(tài)性檢測(cè),亦未發(fā)現(xiàn)FA2H基因缺失突變;例3為雜合突變c.688G>A(p.Glu230Lys)和插入突變c.172_173insGGGCCAGGAC(p.Ile58ArgfsX47,圖4),此2種突變?cè)诩蚁抵谐霈F(xiàn)共分離現(xiàn)象;例4為復(fù)合雜合突變c.688G>A(p.Glu230Lys)、c.968C>A(p.Pro323Gln)和c.976G>A(p.Gly326Asp,圖5),其父為c.688G>A(p.Glu230Lys)突變攜帶者,其母為c.968C>A(p.Pro323Gln)和 c.976G>A(p.Gly326Asp)突變攜帶者.根據(jù)美國(guó)醫(yī)學(xué)遺傳學(xué)和基因組學(xué)會(huì)標(biāo)準(zhǔn)[5]進(jìn)行致病性突變判定,例1的FA2H基因雜合突變c.461G>A(p.Arg154His)為"可能致病"、c.794T>G(p.Phe265Cys)為"可能致病";例2的FA2H基因雜合突變c.703C>T(p.Arg235Cys)為"可能致病";例3的FA2H基因雜合突變c.688G>A(p.Glu230Lys)為"致病"、插入突變c.172_173insGGGCCAGGAC(p.Ile58ArgfsX47)為"致病";例4的FA2H基因雜合突變c.688G>A(p.Glu230Lys)為"致病"、c.968C>A(p.Pro323Gln)為"致病"、c.976G>A(p.Gly326Asp)為"可能致病".

圖2 例1 Sanger測(cè)序顯示,FA2H基因存在復(fù)合雜合突變c.461G>A(p.Arg154His,箭頭所示,左圖)和c.794T>G(p.Phe265Cys,箭頭所示,右圖)Figure 2 Sanger sequencing in Case 1 showed FA2H gene compound heterozygous mutation c.461G>A (p.Arg154His,arrow indicates,left panel)and c.794T>G(p.Phe265Cys,arrow indicates,right panel).

圖3 例2 Sanger測(cè)序顯示,FA2H基因存在雜合突變c.703C>T(p.Arg235Cys,箭頭所示)Figure 3 Sanger sequencing in Case 2 showed FA2H genecompound heterozygousmutation c.703C>T (p.Arg235Cys,arrow indicates).

圖4 例3 Sanger測(cè)序顯示,FA2H基因存在雜合突變c.688G>A(p.Glu230Lys,箭頭所示,左圖)和插入突變c.172_173insGGGCCAGGAC(p.Ile58ArgfsX47,箭頭所示,右圖)Figure 4 Sanger sequencing in Case 3 showed FA2H gene compound heterozygous mutation c.688G>A(p.Glu230Lys,arrow indicaties,left panel)and insertion mutation c.172_173insGGGCCAGGAC(p.Ile58ArgfsX47,arrow indicates,right panel).

圖5 例4 Sanger測(cè)序顯示,FA2H基因存在復(fù)合雜合突變c.688G>A(p.Glu230Lys,箭頭所示,左圖)、c.968C>A(p.Pro323Gln,箭頭所示,右圖)和c.976G>A(p.Gly326Asp,箭頭所示,右圖)Figure 5 Sanger sequencing in Case 4 showed FA2H gene compound heterozygous mutation c.688G>A(p.Glu230Lys,arrow indicates,left panel),c.968C>A(p.Pro323Gln,arrow indicates,right panel)and c.976G>A(p.Gly326Asp,arrow indicates,right panel).

討 論

本研究報(bào)道4例FA2H基因突變導(dǎo)致的脂肪酸羥化酶相關(guān)性神經(jīng)變性病患者.FA2H基因編碼FA2H蛋白,包含372個(gè)氨基酸,主要作用是催化脂肪酸N??；溋u化.FA2H蛋白是神經(jīng)酰胺前體,是髓鞘形成關(guān)鍵成分[6].由于磷脂半乳糖脂肪酸在髓鞘脂肪成分中占1/3[7],因此,FA2H蛋白對(duì)維持髓鞘穩(wěn)定性具有重要作用.FA2H基因突變導(dǎo)致FA2H蛋白失活引起羥化作用缺失而影響正常髓鞘形成.異常的髓鞘形成可能促使神經(jīng)元功能障礙和凋亡.FA2H基因突變?cè)徽J(rèn)為與腦白質(zhì)病[2]、SPG35型[3]以及腦組織鐵沉積神經(jīng)變性病相關(guān)[1].由于此3種亞型臨床表現(xiàn)存在重疊,故統(tǒng)稱為脂肪酸羥化酶相關(guān)性神經(jīng)變性病[8],表現(xiàn)為痙攣性截癱、肌張力障礙、癲發(fā)作、視神經(jīng)萎縮、智力減退、小腦萎縮、腦白質(zhì)病變和腦組織鐵離子沉積等.目前全球僅有 56 例報(bào)道[2?3,8?19].

本研究4例患者均于幼年時(shí)期出現(xiàn)痙攣性截癱,而總結(jié)已報(bào)道的脂肪酸羥化酶相關(guān)性神經(jīng)變性病病例,所有患者均存在痙攣性步態(tài),且為首發(fā)癥狀,因此痙攣性截癱是脂肪酸羥化酶相關(guān)性神經(jīng)變性病最常見和最突出的亞型,既往將FA2H基因突變導(dǎo)致的痙攣性截癱定義為SPG35型,系復(fù)雜型遺傳性痙攣性截癱,常合并肌張力障礙、共濟(jì)失調(diào)、構(gòu)音障礙、智力減退和癲發(fā)作等臨床癥狀.本研究有3例患者(例2、例3和例4)符合復(fù)雜型遺傳性痙攣性截癱臨床表現(xiàn),而例1臨床表型為緩慢進(jìn)展的晚發(fā)型單純型遺傳性痙攣性截癱,無智力減退和癲發(fā)作,頭部MRI顯示輕度腦白質(zhì)病變、小腦萎縮和腦組織鐵離子沉積,無明顯胼胝體萎縮,從而拓展SPG35型和脂肪酸羥化酶相關(guān)性神經(jīng)變性病表型譜.值得注意的是,隨著分子檢測(cè)技術(shù)的普及,已有數(shù)項(xiàng)研究報(bào)道非典型SPG35型或脂肪酸羥化酶相關(guān)性神經(jīng)變性病[11,16],其共同點(diǎn)是發(fā)病年齡較晚,癥狀較輕,進(jìn)展緩慢,影像學(xué)無腦白質(zhì)病變或腦組織鐵離子沉積,提示在常染色體隱性遺傳性遺傳性痙攣性截癱中,FA2H基因突變導(dǎo)致的SPG35型或脂肪酸羥化酶相關(guān)性神經(jīng)變性病并不少見.近期在漢族復(fù)雜型常染色體隱性遺傳性遺傳性痙攣性截癱研究中發(fā)現(xiàn),SPG35型發(fā)病率為2.32%,僅次于SPG11型(11.62%)[12].另一項(xiàng)針對(duì)合并胼胝體萎縮、智力減退或腦白質(zhì)病變的復(fù)雜型常染色體隱性遺傳性遺傳性痙攣性截癱研究顯示,SPG35型發(fā)病率(4.91%)亦低于SPG11型(26.22%),但高于SPG48型(3.27%)[11].提示對(duì)于復(fù)雜型常染色體隱性遺傳性遺傳性痙攣性截癱患者,應(yīng)考慮SPG35型或脂肪酸羥化酶相關(guān)性神經(jīng)變性病的可能,而不僅局限于合并癲發(fā)作、認(rèn)知功能障礙、腦白質(zhì)病變、腦組織鐵離子沉積的遺傳性痙攣性截癱.

此外,總結(jié)文獻(xiàn)報(bào)道的56例脂肪酸羥化酶相關(guān)性神經(jīng)變性病患者發(fā)現(xiàn),脂肪酸羥化酶相關(guān)性神經(jīng)變性病中癲發(fā)作發(fā)生率僅為29.09%,提示癲發(fā)作可能是脂肪酸羥化酶相關(guān)性神經(jīng)變性病的特征性表現(xiàn)但不具有普遍性,而構(gòu)音障礙、智力減退發(fā)生率較高.此外,脂肪酸羥化酶相關(guān)性神經(jīng)變性病影像學(xué)表現(xiàn)為腦白質(zhì)病變及小腦和腦干萎縮,與臨床表現(xiàn)上的構(gòu)音障礙和智力減退相符,而腦組織鐵離子沉積和胼胝體萎縮相對(duì)少見.因此,對(duì)于存在構(gòu)音障礙、智力減退同時(shí)伴腦白質(zhì)病變、小腦萎縮的遺傳性痙攣性截癱患者,應(yīng)考慮脂肪酸羥化酶相關(guān)性神經(jīng)變性病的可能.

本研究有2例患者(例3和例4)臨床表現(xiàn)為典型脂肪酸羥化酶相關(guān)性神經(jīng)變性病表現(xiàn),例3目前年齡尚小,是否會(huì)出現(xiàn)癲發(fā)作、認(rèn)知功能障礙尚待進(jìn)一步隨訪觀察.該2例患者FA2H基因突變根據(jù)美國(guó)醫(yī)學(xué)遺傳學(xué)和基因組學(xué)會(huì)標(biāo)準(zhǔn)[5]均判定為"致病",且例3為插入突變,該突變可以導(dǎo)致終止密碼子提前出現(xiàn),從而導(dǎo)致蛋白截短或蛋白功能缺失,由此推測(cè)例3臨床表現(xiàn)可能與典型脂肪酸羥化酶相關(guān)性神經(jīng)變性病相符.例4存在3種FA2H基因雜合突變,共分離研究顯示,c.688G>A(p.Glu230Lys)位于一條染色體,c.968C>A(p.Pro323Gln)和c.976G>A(p.Gly326Asp)則位于另一條染色體,根據(jù)脂肪酸羥化酶相關(guān)性神經(jīng)變性病呈常染色體隱性遺傳的特性,一般認(rèn)為c.968C>A(p.Pro323Gln)和c.976G>A(p.Gly326Asp)中的一個(gè)為致病性突變位點(diǎn),根據(jù)美國(guó)醫(yī)學(xué)遺傳學(xué)和基因組學(xué)會(huì)標(biāo)準(zhǔn)[5]判定c.968C>A(p.Pro323Gln)為"致病",而c.976G>A(p.Gly326Asp)為"可能致病",因此傾向c.968C>A(p.Pro323Gln)為致病性突變,仍不能排除2種突變均造成酶功能改變而致病的可能,尚待進(jìn)一步功能學(xué)試驗(yàn)證實(shí).例1臨床表型為非典型脂肪酸羥化酶相關(guān)性神經(jīng)變性病,存在FA2H基因復(fù)合雜合突變c.461G>A(p.Arg154His)和 c.794T>G(p.Phe265Cys),均為未報(bào)道的錯(cuò)義突變,對(duì)蛋白功能影響尚不明確,但2個(gè)突變位點(diǎn)高度保守,而與c.461G>A(p.Arg154His)位點(diǎn)相鄰、導(dǎo)致相同氨基酸位點(diǎn)改變的純合突變c.460C>T(p.Arg154Cys)曾被報(bào)道導(dǎo)致相同疾病的發(fā)生[1],故根據(jù)美國(guó)醫(yī)學(xué)遺傳學(xué)和基因組學(xué)會(huì)標(biāo)準(zhǔn)[5]判斷為"可能致病",上述2種突變對(duì)酶活性的影響尚待進(jìn)一步研究.由于例1患者表現(xiàn)為非典型脂肪酸羥化酶相關(guān)性神經(jīng)變性病,我們推測(cè)復(fù)合雜合錯(cuò)義突變導(dǎo)致酶活性部分下降可能是潛在原因;而部分非典型脂肪酸羥化酶相關(guān)性神經(jīng)變性病患者腦白質(zhì)病變程度較輕或不存在腦白質(zhì)病變[16],可能與酶活性部分保留可維持部分髓鞘磷脂形成有關(guān)[20],尚待進(jìn)一步功能學(xué)試驗(yàn)驗(yàn)證.例2患者表型符合脂肪酸羥化酶相關(guān)性神經(jīng)變性病的特征性表現(xiàn),主要表現(xiàn)為幼年期發(fā)病的痙攣性截癱、智力減退、癲發(fā)作等,但FA2H基因檢測(cè)僅發(fā)現(xiàn)1種已報(bào)道的雜合突變c.703C>T(p.Arg235Cys),對(duì)其母進(jìn)行FA2H基因檢測(cè)未發(fā)現(xiàn)該突變,推測(cè)該突變?cè)醋云涓?進(jìn)一步的單核苷酸多態(tài)性檢測(cè)未能發(fā)現(xiàn)患者及其母存在缺失突變,因此是否存在其他遺傳情況以及單一突變?nèi)绾螌?dǎo)致疾病尚不明確,由于脂肪酸羥化酶相關(guān)性神經(jīng)變性病為常染色體隱性遺傳,故單一突變可能會(huì)引起酶羥化功能降低而導(dǎo)致臨床癥狀的出現(xiàn),尚待進(jìn)一步對(duì)該位點(diǎn)進(jìn)行功能學(xué)試驗(yàn)證實(shí).

綜上所述,本研究報(bào)道4例脂肪酸羥化酶相關(guān)性神經(jīng)變性病患者.脂肪酸羥化酶相關(guān)性神經(jīng)變性病表型多樣,但痙攣性截癱是其最主要的臨床表現(xiàn),對(duì)于復(fù)雜型常染色體隱性遺傳性遺傳性痙攣性截癱,尤其合并構(gòu)音障礙、智力減退、腦白質(zhì)病變和小腦萎縮等臨床特征的患者,應(yīng)考慮FA2H基因?qū)е碌闹舅崃u化酶相關(guān)性神經(jīng)變性病.

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Clinicalphenotype and genetic mutation offatty acid hydroxylase?associated neurodegeneration:analysis of four cases

HUANG Xiao?jun1,LIU Xiao?li2,WANG Tian2,SHEN Jun?yi2,CHEN Sheng?di2,TANG Wei?guo3,CAO Li21Department of Neurology,North Department of Ruijin Hospital,School of Medicine,Shanghai Jiaotong University,Shanghai 201801,China
2Department of Neurology and Institute of Neurology,Ruijin Hospital,School of Medicine,Shanghai Jiaotong University,Shanghai 200025,China
3Department of Neurology,Zhoushan Hospital,Zhoushan 316021,Zhejiang,China

CAO Li(Email:caoli2000@yeah.net)

ObjectiveTo report 4 cases of fatty acid hydroxylase?associated neurodegeneration(FAHN)and tosummarizethe clinicaland geneticcharacteristicsofFAHN byliteraturesreview.MethodsFour cases of FAHN patients'clinical and family data were collected in detail.The gDNA of patients and their parents were extracted from peripheral blood.FA2H gene was conducted and followed by Sanger sequencing.ResultsAmong the 4 cases,3 cases(Case 2,Case 3,Case 4)presented typical manifestations of FAHN while the other(Case 1)was atypical.Genetic sequencing showed FA2H gene mutation in all affected patients.Compound heterozygous mutation c.461G>A(p.Arg154His)and c.794T>G(p.Phe265Cys)were seen in Case 1.In Case 2,only one documented heterozygous mutation c.703C>T(p.Arg235Cys)was found,and dificit mutation was not found in single nucleotide polymorphism(SNP)chip test of the patient and her mother. Compound heterozygous mutation c.688G>A (p.Glu230Lys)and insertion mutation c.172_173insGGGCCAGGAC(p.Ile58ArgfsX47)were presented in Case 3.In Case 4,compound heterozygous mutation c.688G>A(p.Glu230Lys),c.968C>A(p.Pro323Gln)and c.976G>A(p.Gly326Asp)were seen,while his father was the carrier of c.688G>A(p.Glu230Lys)mutation and his mother was the carrier of c.968C>A(p.Pro323Gln)and c.976G>A(p.Gly326Asp)mutation.According to the standard of American College of Medical Genetics and Genomics(ACMG),c.461G>A(p.Arg154His)and c.794T>G(p.Phe265Cys)in Case 1,and c.703C>T(p.Arg235Cys)in Case 2 were considered as"likely pathogenic",while FA2H gene compound heterozygous mutation c.688G>A(p.Glu230Lys),insertion mutation c.172_173insGGGCCAGGAC(p.Ile58ArgfsX47)in Case 3 was as"pathogenic",and in Case 4,the FA2H gene mutation c.688G>A(p.Glu230Lys)and c.968C>A(p.Pro323Gln)were"pathogenic"and c.976G>A(p.Gly326Asp)was"likely pathogenic".ConclusionsFAHN has highly clinical and genetic heterogenieity in which spastic paraplegia is the main clinical presentation.In typing diagnosis for patietns with autosomal recessive herditary spastic paraplegia(HSP),especially combined with dyslalia,dysnoesia,and clinical features of white matter lesion and cerebellar atrophy,FA2H gene mutation?induced FAHN should be considered.

Neurodegenerative diseases; Fatty acids; Mixed function oxygenases; Phenotype;Genes; Mutation

10.3969/j.issn.1672?6731.2017.07.010

國(guó)家自然科學(xué)基金資助項(xiàng)目(項(xiàng)目編號(hào):81571086);國(guó)家自然科學(xué)基金青年科學(xué)基金資助項(xiàng)目(項(xiàng)目編號(hào):81600978);上海交通大學(xué)醫(yī)學(xué)院高峰高原計(jì)劃(項(xiàng)目編號(hào):20161401);上海交通大學(xué)"醫(yī)工交叉研究基金"資助項(xiàng)目(項(xiàng)目編號(hào):YG2016MS64);浙江省科學(xué)技術(shù)廳2014年度公益性技術(shù)應(yīng)用研究計(jì)劃項(xiàng)目(項(xiàng)目編號(hào):2014C33132)

201801上海交通大學(xué)醫(yī)學(xué)院附屬瑞金醫(yī)院北院神經(jīng)內(nèi)科(黃嘯君);200025上海交通大學(xué)醫(yī)學(xué)院附屬瑞金醫(yī)院神經(jīng)科 上海交通大學(xué)醫(yī)學(xué)院神經(jīng)病學(xué)研究所(劉曉黎,王田,沈雋逸,陳生弟,曹立);316021浙江省舟山醫(yī)院神經(jīng)內(nèi)科(唐維國(guó))

曹立(Email:caoli2000@yeah.net)

This study was supported by the National Natural Science Foundation of China(No.81571086),the National Natural Science Foundation of China for Young Scientists(No.81600978),Shanghai Jiaotong University School of Medicine Peak and Plateau Program (No.20161401),Crossing Program between Medicine and Industry supported by Shanghai Jiaotong University(No.YG2016MS64),and Non?Profit Technical Application Plan Project of Science Technology Department of Zhejiang Province,China in the Year 2014(No.2014C33132).

2017?06?24)