Clin Genet 2013Printed in Singapore. All rights reserved

© 2013 John Wiley & Sons A/S.Published by Blackwell Publishing Ltd

CLINICAL GENETICSdoi: 10.1111/cge.12120

Short Report

Clinical features of Chinese patients withHuntington’s disease carrying CAG repeatsbeyond 60 within HTT gene

Liu Z-J, Sun Y-M, Ni W, Dong Y, Shi S-S, Wu Z-Y. Clinical features ofChinese patients with Huntington’s disease carrying CAG repeats beyond60 within HTT gene.Clin Genet 2013. © John Wiley & Sons A/S. Published by BlackwellPublishing Ltd, 2013

Patients with Huntington’s disease (HD) carrying CAG repeats beyond 60are less frequently seen and clinical features of them have been rarelyreported. We identified four unrelated patients carrying CAG repeatsbeyond 60 (84.0 ± 13.76, ranging from 74 to 104) from 119 Chinese HDpatients via direct sequencing. These four were all early onset with a meanage at presenting symptom of 9.8 ± 1.71 years. Paternal transmission wasfound in three of them and the fourth was apparently sporadic. In addition,they had atypical onset symptoms including epilepsy, intellectual decline,tics and walking instability, which might lead the clinicians to make thewrong diagnosis in the early stage of disease. Our work explores clinicalfeatures of Chinese HD patients with an expanded CAG repeat over 60and may help the clinicians make a correct diagnosis in the early stage ofdisease.

Conflict of interest

The authors report no conflicts of interest.

Z-J Liua,b,†, Y-M Suna,†, W Nia,b,Y Donga, S-S Shia and Z-Y Wua

aDepartment of Neurology and Institute ofNeurology, Huashan Hospital, Institutesof Brain Science and State KeyLaboratory of Medical Neurobiology,Shanghai Medical College, FudanUniversity, Shanghai, China andbDepartment of Neurology and Instituteof Neurology, First Affiliated Hospital,Fujian Medical University, Fuzhou, China

†These authors contributed equally to thiswork.

Key words: CAG repeats beyond 60 –Huntington’s disease – HTT

Corresponding author: Zhi-Ying Wu,MD, PhD, Department of Neurologyand Institute of Neurology, HuashanHospital, Institutes of Brain Science andState Key Laboratory of MedicalNeurobiology, Shanghai MedicalCollege, Fudan University, 12 WulumuqiZhong Road, Shanghai 200040, China.Tel: +86 21 62483421;fax.: +86 21 62483421;e-mail: zhiyingwu@fudan.edu.cn

Received 13 December 2012, revisedand accepted for publication 5February 2013

Huntington’s disease (HD) is an autosomal dominantinherited neurodegenerative disease. It usually startsinsidiously in mid-adult life with characteristic mani-festations of progressive motor dysfunction, cognitiveimpairment and psychological disorders (1). HD iscaused by an unstable CAG triplet repeats expansionin exon 1 of HTT gene with at least 36 repeats (2, 3).It has been proven by many studies that CAG repeatlength is inversely related to age at onset (AAO) (4, 5).

Large CAG expansion over 60 accounts for 4% ofthe spectrum of HTT mutation (6) and HD patientswith large expansion (>60 CAG repeats) developsymptoms at an early age, usually with rapid progres-sion and atypical motor disorders other than chorea(7–9). It is reported that the expanded CAG repeatsize of juvenile-onset HD (JHD) usually exceeds 60(10, 11). But it could also be below 59 and evenas low as 41 (12–14). Most of the reports focus onJHD and little concerns about the clinical features of

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Table 1. Initial symptom of Huntington’s disease (HD) patients

HD patients

Initial symptom

Patients with CAGrepeats beyond 60

(n = 4)

Patients with CAGrepeats below 60

(n = 115)

Seizures 1 (25%) 0Intellectual decline 1 (25%) 2 (1.7%)Walking instability 1 (25%) 7 (6.1%)Tics in limbs 1 (25%) 2 (1.7%)Ataxia 0 7 (6.1%)Psychiatric disorder 0 4 (3.5%)Chorea movement 0 91 (79.2%)Memory declined 0 2 (1.7%)

HD patients with a length of CAG repeat over 60,especially in China. To our knowledge, there were onlytwo individual case reports on Chinese HD patientswith CAG repeats beyond 60 (15, 16).

Here, we describe the clinical and genetic features offour unrelated patients carrying CAG repeats beyond60 after investigating 119 HD patients. We attempt toexplore clinical features of HD with large expansion(>60 CAG repeats) in Chinese HD patients andhelp clinicians recognize it in the early stage of thedisease.

Materials and methods

Subjects

One hundred and nineteen Chinese Han HD patientsfrom 110 families confirmed by genetic testing wererecruited. They were from Southeastern China andenrolled consecutively in Genetic Clinic of HuashanHospital between February 2008 and October 2012.Their clinical data were investigated retrospectively.The study was approved by the ethics committee ofHuashan Hospital. Informed consents were signedby patients or the parents of patients younger than18 years old.

Genetic analysis of CAG repeats in HTT gene

Genomic DNA was extracted from peripheral ethylenediamine tetraacetic acid (EDTA)-treated blood usingBlood Genomic Extraction Kit (Lifefeng BiotechnologyCo., Ltd., Shanghai, China). Genetic testing was

conducted for all 119 patients, as previously reported(17), and CAG repeat sizes were further determined bydirect sequencing.

Results

Genetic analysis of HTT gene

Among 119 HD patients, 4 were found carrying CAGrepeats beyond 60, which were estimated by elec-trophoresis analysis (Fig. S1, Supporting Information)and further confirmed by sequencing (Figs S2–S5).Mean expanded CAG repeat number of these fourpatients was much larger than that of the other 115patients (84.0 ± 13.76 vs 45.3 ± 3.64). The repeat sizesfor the affected uncle of patient 3 and affected fatherof patient 4 was 17/53 and 16/45, respectively (Figs S6and S7), much smaller than that of the proband.

Clinical features

The mean AAO of the four patients with large CAGexpansion was much earlier than that of the other 115patients (9.8 ± 1.71 vs 40.2 ± 10.75 years). The averagedelayed time from onset to molecular diagnosis in thesefour patients was 4.0 ± 2.16 years, ranging from 2 to7 years. In addition, they started with atypical symptomswhile the other 115 patients begun with characteristicHD symptoms (Table 1). The characteristics of thesefour patients were summarized in Table 2.

Patient 1 (Fig. 1; family 1, IV1) started with frequentseizures during sleep time at age 8. He primarilypresented with jerking in upper limbs during the ictalperiod and each episode lasted for 1–2 min. Then, hegradually developed shrug in the right shoulder andexhibited poor attention and impaired intelligence. Onneurological examination, the nystagmus was negative.Ankle clonus and Babinski’s sign were positive.Muscle tone of lower limbs and tendon reflexeswere increased. Epileptiform discharges were depictedon electroencephalograph. He died at age 11 withan unclear cause. All his family members in fourgenerations were affected except one of his uncles.Their AAO ranged from 30 to 40 years and the averagedisease course was about 10 years. Of all the affectedfamily members, only his younger aunt was still alivewith a disease course of 2 years.

Patient 2 (Fig. 1; family 2, III1) started with ticsin limbs at age 10. The tics were always quickand jerky just like the typical tics manifestation in

Table 2. Characteristics of four patients carrying CAG repeats beyond 60

Characteristics Patient 1 Patient 2 Patient 3 Patient 4

Age at onset (years)/gender 8/male 10/male 9/male 12/femaleAge at diagnosis (years) 10 13 13 19Onset symptom Seizures Tics in limbs Intellectual decline Walking instabilityNumber of CAG repeats 17/104 18/82 17/76 17/74Inheritance Paternal No family history Paternal Paternal

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Fig. 1. Pedigrees of four Huntington’s disease patients carrying CAGrepeats beyond 60. The arrows indicate the probands.

Tourette’s syndrome. He experienced gait disorder andslurred speech and gradually developed involuntarynictation and wiggle of head, which existed evenduring sleep. Foot dystonia was observed and seemedlike ‘Pes adductus’. Neurological examination revealedincreased muscle tone. No family history was reported.The request of genetic testing to his parents wasdeclined.

Patient 3 (Fig. 1; family 3, III1) started with intellec-tual decline at age 9. Three years later, he complainedclumsiness in the left hand and gradually exhibiteddysarthria and drop attacks. He was incommunicative.On neurological examination, nystagmus was negative.Tendon reflexes were brisk and Babinski’s sign waspositive. His father and three uncles were all affectedwith AAO of 20–35 years. His father and grandfathercommitted suicide at age 37 and 50, respectively.

Patient 4 (Fig. 1; family 4, III1) started with walk-ing instability and gradually exhibited bradykinesia,dysphagia and speech with a lisp. She developed akyphosis due to the severe trunk dystonia. On neuro-logical examination, ataxia signs were evident. Mus-cle tone and tendon reflexes were all increased. Ankleclonus was positive. Slow saccades were observed andnystagmus was negative. She was initially clinicallydiagnosed as spinocerebellar ataxia (SCA). Her grand-mother started mild chorea of the four limbs at age 45and died at 57. Her father was 36 years old without anysigns so far despite his expanded CAG repeat numberwas 45.

During the course of disease, typical HD manifes-tations, like chorea, cognitive impairment, and psy-chological disorder gradually occurred in all fourpatients.

Neuroimaging

Cerebral atrophy was observed in all four patients oncomputerized tomography (CT) or magnetic resonanceimaging (MRI). The abnormal signals were seen inbilateral basal ganglia of patients 1 and 4. In patient 4,the caudate and putamen nucleus were symmetrically

atrophied while the slightly atrophic brainstem andcerebellum were also seen (Fig. 2).

Discussion

According to previous reports, we found those HDpatients carrying CAG repeats beyond 60 had the fol-lowing characteristics. First, they mainly had earlyonset. CAG repeats beyond 60 were responsible forapproximately half of JHD and CAG repeats over 80might cause childhood-onset HD (6, 18). Second, theirmanifestations were atypical, in which rigidity, bradyki-nesia, intellectual decline, behavior change, frequentfalls, speech impairment, seizures, and ataxia were theinitial or predominant (7, 14, 19–24). In addition, ini-tial symptoms including excessive blinking, attentiondeficits, gait disorder, and global developmental delaywere also observed (25–27). Third, paternal trans-mission was predominant pattern of inheritance (19).Fourth, the atrophies in cerebral cortex, striatum or cere-bellum and increased density in T2-weighted signal incaudate and putamen nuclei in MRI were characteristicimaging features (12, 23, 28).

In this study, all four patients presented with atyp-ical symptoms at early stage. Onset with epilepsyand intellectual decline were observed in two patientsand non-choreiform movements occurred in the othertwo patients. Attention deficits, ataxia, dysphagia, gaitdisorder, bradykinesia and speech impairment werealso observed. These features were in accordancewith the characteristics summarized above. The neu-roimaging features of our four patients were sim-ilar to those reported previously (12, 28). Unfor-tunately, the images of patients 1, 2 and 3 weremissing.

Concerning about inheritance, three pedigreesshowed paternal transmission except for pedigree 2whose family history was obscure. In addition, rapiddownhill course and familial clustering were found inpedigrees 1 and 3, whose family members were alsoseverely affected. Conversely, this phenomenon wasnot observed in the pedigree 2 in which family historywas absent. This interesting finding indicated clinicalphenotypes could be different between the pedigreeswith obvious family history and those with obscurefamily history. These preliminary data needs to befurther confirmed in a larger cohort.

Patient 4 presented with walking instability inearly stage of disease, which might be mistaken asSCA, since SCA was prevalent in Chinese popu-lation (29) and could also be juvenile onset (30).Although both JHD and juvenile-onset SCA patientsmight share the cerebellum signs, other featuresof HD were helpful to distinguish it from SCA,including saccade initiation delay, saccadic slowing,gaze impersistence and motor impersistence (7, 17,29–32). Slow saccades were observed in patient 4, butother valuable signs like saccade initiation were notrecorded.

In summary, among 119 Chinese HD patients, weidentified four atypical patients carrying CAG repeats

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Fig. 2. The brain magnetic resonance image (MRI) of patient 4 at the age of 14 years. The sagittal (a) sections reveal brainstem and cerebellumatrophy (arrow). (b–d) Atrophy and abnormal signals of the caudate and putamen nuclei (arrows) in T1 (b), T2 (c) and T2-FLAIR (d) weightedimaging.

beyond 60. The present report added information on therare phenotype in Chinese HD patients carrying largeCAG repeats and attempted to help the clinicians makea correct diagnosis in the early stage of disease.

Supporting Information

The following Supporting information is available for this article:

Fig. S1. The 1.5% agarose gel electrophoresis analysis of sixHuntington’s disease (HD) patients from four families. M: DL2000DNA molecular weight marker; 1: an identified HD patient (17/58);2–5: patients 1–4 carrying CAG repeats beyond 60 (17/104, 18/82,17/76, and 17/74); 6: the affected uncle (17/53) of patient 3; 7: theaffected father of patient 4 (16/45).Fig. S2. Chromatogram of patient 1 with CAG repeats of 17/104.Fig. S3. Chromatogram of patient 2 with CAG repeats of 18/82.Fig. S4. Chromatogram of patient 3 with CAG repeats of 17/76.Fig. S5. Chromatogram of patient 4 with CAG repeats of 17/74.Fig. S6. Chromatogram of II6 in pedigree 3 with CAG repeats of17/53.Fig. S7. Chromatogram of II1 in pedigree 4 with CAG repeats of16/45.

Additional Supporting information may be found in the onlineversion of this article.

Acknowledgements

The authors sincerely thank the patients for their help andwillingness to participate in this study. We also thank theanonymous reviewers for helpful comments. This work wassupported by grants from the National Natural Science Foundationto Z. -Y. W. (81125009, Beijing).

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