DYT1 mutation in primary torsion dystonia in a Serbian population

Primary torsion dystonia (PTD) is a clinically and genetically heterogeneous movement disorder. A GAG deletion at position 946 in the DYT1 gene is responsible for most cases of autosomal dominant early-onset PTD. We analysed the DYT1 mutation in 50 patients from a Serbian population, selected according to the proposed guidelines for diagnostic testing: (a) 38 patients with PTD onset < 26 years, and (b) 12 patients with the disease onset ± 26 years, but with at least one affected family member with early-onset dystonia. Only three apparently sporadic patients among the 50 individuals tested were positive for the GAG deletion in the DYT1 gene: one with typical, generalized, one with long-lasting, non-progressive segmental, and one with multifocal dystonia. Molecular analysis of relatives in 2 families revealed that the lack of family history was due to reduced penetrance. Received: 29 December 2000, Received in revised form: 23 March 2001, Accepted: 10 April 2001     

Phenotypic variability of DYT1‐PTD: Does the clinical spectrum include psychogenic dystonia?

Primary torsion dystonia (PTD) is a clinically and genetically heterogeneous group of movement disorders, usually inherited in an autosomal dominant manner with reduced (30-40%) penetrance. The DYT1 gene on chromosome 9q34 is responsible for most cases of early limb-onset PTD. DYT1-PTD clinical spectrum is broad, as the disease may present with several degrees of body involvement and severity. We identified an Italian family with 4 members definitely affected by PTD, genetically diagnosed as carriers of the GAG mutation at DYT1 gene. Phenotype was homogeneous when considering the presentation at onset (limb involvement and early onset), the disease progression was variable; in the subjects of the last generation, the disease progressed to a severe, generalized PTD; in the remaining 2 subjects, dystonia presented with writer's cramp or upper body segmental dystonia of mild severity. One family member, carrier of the GAG mutation on DYT1 gene and mother of the most severely affected individual, presented with a clinically established psychogenic movement disorder resembling dystonia initially diagnosed as a severe generalized PTD. Psychogenic movement disorders are among the most controversial and challenging diseases to diagnose, in particular when the affected individual belongs to a family with an inherited movement disorder.     

A Yorkshire family with adult-onset cranio-cervical primary torsion dystonia.

Although a family history is described in approximately 20% of patients, large families with adult-onset craniocervical primary (idiopathic) torsion dystonia (PTD) are rare. We report a new British family with cranio-cervical dystonia. Seventeen members of the family were examined. Five cases were diagnosed as definite PTD and one as probable PTD. Mean age at onset was 29 years (range, 19-40 yrs). The phenotype was characterized by adult-onset cranio-cervical dystonia in all affected cases. A few cases had additional voice tremor and/or postural arm tremor. The GAG deletion in the DYT1 gene was excluded in the index case. Linkage analysis was performed between the disease and several marker loci spanning DYT6 and DYT7 regions, and haplotypes were reconstructed in all subjects. Although linkage analysis was not completely informative, reconstructed haplotypes excluded linkage between the disease and either DYT6 or DYT7. This report confirms that familial cranio-cervical dystonia is genetically heterogeneous, and further studies of other PTD families with similar clinical features are needed to identify other new genes.     

Non-DYT1 early-onset primary torsion dystonia: comparison with DYT1 phenotype and review of the literature.

To investigate the clinical features of early-onset primary torsion dystonia (EO-PTD), 57 consecutive genetically characterized patients with onset before 21 years were studied. Sex, ethnic origin, family history of dystonia, age at onset, disease duration, site of dystonia onset and distribution at latest examination, dystonia progression, time to generalization, and motor disability were noted. The 14 patients (25%) with GAG deletion (904_906/907_909delGAG) in the DYT1 gene were compared with the remaining non-DYT1 patients. Cranial involvement was present in 49% of non-DYT1 cases, but only 14% of DYT1 cases; non-DYT1 patients were younger at time of generalization. DYT1 cases had features similar to sporadic non-DYT1 cases but differed markedly from familial non-DYT1 cases, the latter having later age at onset, less common limb onset, more frequent cervical involvement, and slower progression than DYT1 PTD. These findings indicate that non-DYT1 forms of EO-PTD differ clinically from those of DYT1 forms. Cranial involvement before 21 years of age is the strongest predictor of non-DYT1 status. Positive family history and cervical involvement are associated with less severe progression in non-DYT1 forms.     

Dystonia in Ashkenazi Jews: Clinical characterization of a founder mutation

A gene (DYT1) for idiopathic torsion dystonia maps to chromosome 9q34 in Ashkenazi Jewish families with early onset of symptoms. Further, there is linkage disequilibrium between DYT1 and a particular haplotype of alleles at 9q34 loci in this population. This implies that a large proportion of early-onset idiopathic torsion dystonia in Ashkenazi Jews is due to a founder mutation in DYT1. To characterize the phenotypic range of this mutation, we studied 174 Ashkenazi Jewish individuals affected with idiopathic torsion dystonia. We used GT(n) markers on chromosome 9q34 (D9S62, D9S63, and ASS) and classified individuals as having (“carriers”), not having (“noncarriers”), or being ambiguous with respect to a DYT1-associated haplotype. We assessed clinical features and found marked clinical differences between haplotype carriers and noncarriers. There were 90 carriers, 70 noncarriers, and 14 ambiguous individuals. The mean age at onset of symptoms was significantly lower in carriers than in noncarriers (12.5 ± 8.2 vs 36.5 ± 16.4 years). In 94% of carriers, symptoms began in a limb (arm or leg equally); rarely the disorder started in the neck (3.3%) or larynx (2.2%). In contrast, the neck, larynx, and other cranial muscles were the sites of onset in 79% of noncarriers; onset in the arms occurred in 21% and onset in the legs never occurred. Limb onset, leg involvement in the course of disease, and age at onset distinguished haplotype carriers from noncarriers with 90% accuracy. In conclusion, there are clinical differences between Ashkenazi Jewish individuals with idiopathic torsion dystonia who do or do not have a unique DYT1 mutation, as determined by a DYT1-associated haplotype of 9q34 alleles. These differences suggest that early, limb-onset idiopathic torsion dystonia and late, cervical cranial–onset idiopathic torsion dystonia are genetically distinct entities.     

Italian family with cranial cervical dystonia: clinical and genetic study.

A white Italian family affected by primary torsion dystonia (PTD) is described. The family phenotype most commonly presented with adult onset, cranial cervical involvement, and focal or segmental distribution without progression to generalization. Thirty-nine family members and nine spouses were studied. Five subjects received a diagnosis of definite PTD, three of probable PTD. Age at onset was in adulthood for all. In four definitely affected subjects, dystonia started in the cranial or cervical districts; in one it presented as writer's cramp. Familial writer's cramp also occurred in the family of the unrelated parent of the latter patient. The mean age at time of examination was 61.8 years in the individuals with a definite diagnosis; 60 in those with a probable diagnosis. At the time of examination, in most of the affected subjects, dystonia was focal; in three cases (two definitely and one probably affected), it was segmental. DNA linkage analysis, although limited by the size of the family, suggested exclusion of linkage between the disease and known PTD loci (DYT6 and DYT7). The GAG deletion in the DYT1 gene was excluded in the proband and in the family member affected by writer's cramp.     

Diagnostic criteria for dystonia in DYT1 families

Family studies of primary torsion dystonia have used the diagnostic categories of definite, probable, and possible dystonia for gene mapping and identification, but the validity of this hierarchical classification is not known. The authors assessed 147 DYT1 GAG deletion carriers and 113 blood-related noncarriers from 43 families. Only the category of definite dystonia was 100% specific. Probable dystonia, but not possible, was increased in carriers compared with noncarriers. The authors recommend that only those with definite signs of dystonia be considered affected in linkage and other genetic studies.     

Atypical phenotypes and clinical variability in a large Italian family with DYT1-primary torsion dystonia.

The GAG deletion in the DYT1 gene usually causes a typical form of primary torsion dystonia (PTD) with early onset in a limb, rapid generalization, and sparing of cranial-cervical muscles, but atypical phenotypes have often been reported. Here, we describe a large DYT1 Italian family with phenotypically heterogeneous PTD that recapitulates all the atypical features associated with the DYT1 mutation, including late age at onset, focal or segmental phenotypes, onset or spreading of dystonia to the cranial-cervical muscles. Of 38 healthy family members, 15 also carried the DYT1 mutation, with an estimated penetrance of 21%. A literature review of atypical familial cases of DYT1-PTD showed that late onset, cervical involvement, and limited progression of dystonia are features frequently seen in DYT1 families. However, nearly all of these atypical patients fall within at least one of the clinical categories that best predict the DYT1 carrier status, namely, early onset, onset in a limb, and family history positive for early-onset dystonia.     

Identification of a novel primary torsion dystonia locus (DYT13) on chromosome 1p36 in an Italian family with cranial-cervical or upper limb onset

Primary torsion dystonia (PTD) is a clinically and genetically heterogeneous group of movement disorders, usually inherited in an autosomal dominant fashion. Three PTD loci (DYT1, DYT6 and DYT7) have been identified to date. However, in several PTD families linkage to the known loci has been excluded. We identified an Italian PTD family with 11 definitely affected members. Phenotype was characterised by juvenile or early-adult onset, prominent cranial-cervical and upper limb involvement, mild course and occasional generalisation. A genome-wide search performed in the family identified a novel PTD locus (DYT13) within a 22-cM interval on the short arm of chromosome 1, with a maximum lod score of 3.44 (θ=0) between the disease and marker D1S2667.     

Primary torsion dystonia: the search for genes is not over

A GAG deletion in the DYT1 gene accounts for most early, limb onset primary torsion dystonia (PTD). The genetic bases for the more common adult onset and focal PTD are less well delineated. Genetic loci for an "intermediate dystonia" phenotype and for torticollis, named DYT6 and DYT7 respectively, have recently been mapped in single families. To evaluate the contribution of these genetic loci to other families with familial "non-DYT1" dystonia five large families with dystonia were studied using genetic markers spanning the DYT6 and DYT7 regions. There was no evidence of linkage to either locus in any family. These findings illustrate the genetic heterogeneity of the dystonias and indicate the existence of one or more as yet unmapped genes for dystonia. Large collaborative efforts will be required to identify these, and additional genes, causing PTD.     

Clinical and genetic evaluation in a French population presenting with primary focal dystonia.

Primary focal dystonia (PFD) is known to be a clinically and genetically heterogeneous group of movement disorders. To evaluate the frequency of familial focal dystonia in a French population presenting with PFD, we screened 197 patients (150 index cases and 47 affected family members) presenting focal primary dystonia for the GAG deletion in the DYT1 gene and analyzed linkage to the DYT6, DYT7, and DYT13 loci in those who presented a family history. Fourteen families could be recruited and, among them 47 new symptomatic individuals could be identified by clinical examination. A group of 104 patients were without family history and 46 patients (30.7%) were found to have at least one first-degree relative with dystonia. Mean age at onset was significantly later (55.4 +/- 14.0 years) in the blepharospasm group and earlier in patients with writer's cramp (35.8 +/- 14.0 years). The group of patients with family history showed a mean age at onset significantly earlier (39.2 +/- 18.0) than in patients without family history (47.4 +/- 14.4 years). Fourteen families demonstrated an autosomal mode of transmission and five families were studied further for genetic linkage analysis, but no significant linkage to one of the three loci could be observed. Our results illustrate the importance of genetic factors and the clinical heterogeneity of PFD. They indicate the existence of one or several as yet unmapped genes responsible for these diseases.     

Frequency of the DYT1 mutation in primary torsion dystonia without family history

BACKGROUND: Idiopathic torsion dystonia is a clinically and genetically heterogeneous movement disorder. A GAG deletion at position 946 of the DYT1 gene was the first mutation found, in early-onset dystonia, with an autosomal dominant transmission and reduced penetrance. OBJECTIVE: To evaluate the frequency of the DYT1 mutation in patients with idiopathic torsion dystonia but without a family history. DESIGN: Prospective cohort study. SETTING: Four botulinum toxin clinics in the Paris, France, area. PATIENTS: A French population of 100 patients with dystonia. MAIN OUTCOME: Frequency of the DYT1 mutation tested by polymerase chain reaction and enzyme restriction analysis for the 946 GAG deletion, and genotype-to-phenotype correlation. RESULTS: Only 5 mutation carriers were identified, 4 of whom were part of a group of 10 patients with generalized dystonia. Onset was between ages 5 and 12 years as in typical early-onset dystonia. All 4 patients had cranial muscle involvement, which is atypical for DYT1 mutation carriers. One had segmental dystonia. Molecular analysis of relatives in 2 families demonstrated that the lack of family history was due to reduced penetrance. CONCLUSIONS: For accurate diagnosis and genetic counseling, screening for the DYT1 deletion is of great interest in cases with generalized dystonia without a family history. In other cases, positive results are rare.     

Clinical characteristics of carriers of a GAG deletion in the DYT1 gene amongst Polish patients with primary dystonia

DYT1 primary torsion dystonia is an autosomal dominant disorder caused by deletion of a GAG triplet in exon 5 of the DYT1 gene. A significant proportion of individuals with early-onset generalized dystonia is believed to be DYT1 mutation carriers. We assessed the frequency of the GAG deletion in the DYT1 gene in a group of 61 Polish probands with clinical diagnosis of primary dystonia. The deletion was identified in four probands presenting with early-onset generalized disease (7%). Further studies in probands' families revealed two symptomatic and nine asymptomatic mutation carriers. We tested all mutation-positive individuals for the presence of some common polymorphisms within the DYT1 gene. Two of the 15 mutation-positive individuals additionally carried polymorphisms in 3'-UTR of the gene. Early onset in a limb and progression toward a generalized form, but not family history of dystonia, are indicative of DYT1 dystonia in Polish dystonic individuals.     

Familial blepharospasm is inherited as an autosomal dominant trait and relates to a novel unassigned gene.

Blepharospasm (BSP) is a common form of primary torsion dystonia (PTD). Although most cases are sporadic, an increased familial incidence of BSP has been reported. Precisely how blepharospasm is inherited remains unclear. We report on two Italian families with adult-onset focal BSP inherited as an autosomal dominant trait with reduced penetrance. None of the affected family members had the 3-bp (GAG) or the 18-bp deletion in the DYT1 gene. In one family, linkage analysis allowed us to exclude segregation of the disease with the known PTD loci (DYT1, DYT6, DYT7, and DYT13). These findings suggest that primary familial adult-onset BSP is a distinct entity among inherited PTD and is caused by a novel, unmapped gene. Copyright Movement Disorder Society     

DYT13, a novel primary torsion dystonia locus, maps to chromosome 1p36.13--36.32 in an Italian family with cranial-cervical or upper limb onset

Primary torsion dystonia (PTD) is a clinically and genetically heterogeneous group of movement disorders, usually inherited in an autosomal dominant fashion with reduced penetrance. The DYT1 gene on chromosome 9q34 is responsible for most cases of early limb-onset PTD. Two other PTD loci have been mapped to date. The DYT6 locus on chromosome 8 is associated with a mixed phenotype, whereas the DYT7 locus on chromosome 18p is associated with adult onset focal cervical dystonia Several families have been described in which linkage to the known PTD loci have been excluded. We identified a large Italian PTD family with 11 definitely affected members. Phenotype was characterized by prominent cranial-cervical and upper limb involvement and mild severity. A genome-wide search was performed in the family. Linkage analysis and haplotype construction allowed us to identify a novel PTD locus (DYT13) within a 22 cM interval on the short arm of chromosome 1, with a maximum lod score of 3.44 between the disease and marker D1S2667.     

Heterogeneity in primary dystonia: Lessons from THAP1, GNAL,and TOR1A in Amish‐Mennonites

A founder mutation in the Thanatos‐associated (THAP) domain containing, apoptosis associated protein 1 (THAP1) gene causing primary dystonia was originally described in the Amish‐Mennonites. However, there may be both genotypic and phenotypic heterogeneity of dystonia in this population that may also inform studies in other ethnic groups. Genotyping for THAP1 and for guanine nucleotide binding protein (G protein), α‐activating activity polypeptide, olfactory type (GNAL) mutations and genotype‐phenotype comparisons were performed for 76 individuals of Amish‐Mennonites heritage with primary dystonia. Twenty‐seven individuals had mutations in THAP1—most with the founder indel mutation—but two had different THAP1 mutations, 8 had mutations in GNAL, and 1 had a de novo GAG deletion in torsin 1A (TOR1A) (dystonia 1 [DYT1]). In the primary analysis comparing THAP1 carriers versus all non‐THAP1, non‐GNAL, non‐TOR1A individuals, age at onset was lower in THAP1 carriers (mean age ± standard deviation, 15.5 ± 9.2 years [range, 5‐38 years] vs. 39.2 ± 17.7 years [range, 1‐70 years]; P < 0.001), and THAP1 carriers were more likely to have onset of dystonia in an arm (44.4% vs. 15.0%; P = 0.02) and to have arm involvement (88.9% vs. 22.5%; P < 0.01), leg involvement (51.9% vs. 10.0%; P = 0.01), and jaw/tongue involvement (33.3% vs. 7.5%; P = 0.02) involvement at their final examination. Carriers were less likely to have dystonia restricted to a single site (11.11% in carriers vs. 65.9% in noncarriers; P < 0.01) and were less likely to have dystonia onset in cervical regions (25.9% of THAP1 carriers vs. 52.5% of noncarriers; P = 0.04). Primary dystonia in the Amish‐Mennonites is genetically diverse and includes not only the THAP1 indel founder mutation but also different mutations in THAP1 and GNAL as well as the TOR1A GAG deletion. Phenotype, particularly age at onset combined with final distribution, may be highly specific for the genetic etiology. © 2014 International Parkinson and Movement Disorder Society     

Frequency and phenotypic variability of the GAG deletion of the DYT1 gene in an unselected group of patients with dystonia

BACKGROUND: Dystonia is a clinically and genetically heterogeneous movement disorder characterized by sustained muscle contractions affecting one or more sites of the body, frequently causing twisting and repetitive movements or abnormal postures. A 3-base pair (GAG) deletion in the DYT1 gene is held responsible for most cases of early-onset primary generalized dystonia in the Ashkenazi Jewish population as well as in non-Jewish patients. OBJECTIVES: To investigate the prevalence of the GAG deletion in the DYT1 gene and the phenotypic variability in the general population by testing patients with different subtypes of dystonia from 4 different movement disorder outpatient clinics in Germany. METHODS: Two hundred fifty-six patients were tested for the GAG deletion mutation in the DYT1 gene by means of published primers and polymerase chain reaction amplification to determine GAG deletion status. RESULTS: Six of the 256 patients did carry the GAG-deletion in the DYT1 gene. However, only 2 of the 6 mutation carriers presented with what is thought to represent classic features of early-onset primary generalized dystonia. The DYT1 mutation was also detected in 2 patients with multifocal dystonia, 1 of them presenting with involvement of cranial and cervical muscles, and in 2 patients with writer's cramp of both hands with only slight progression. Our findings demonstrate that the mutation may be associated with not only generalized but also segmental and multifocal forms of dystonia. CONCLUSIONS: Our data underline the wide range of phenotypic variability of the DYT1 mutation. A priori prediction of the mutation carrier status in dystonic patients and genetic counseling of affected families with respect to the clinical manifestation may prove difficult.     

Phenotypic characterization of DYT13 primary torsion dystonia.

We describe the phenotype of DYT13 primary torsion dystonia (PTD) in a family first examined in 1994. A complete neurological evaluation was performed on all available family members: 8 individuals were definitely affected by dystonia. The family was re-evaluated in March 2000: at that time, 3 more individuals had developed symptoms of dystonia. Inheritance of PTD was autosomal dominant, with affected individuals spanning three consecutive generations and male-to-male transmission. Age at onset ranged from 5 to 43 years. Onset occurred either in the craniocervical region or in upper limbs. Progression was mild, and the disease course was benign in most affected individuals; generalization occurred only in 2 cases. We did not find anticipation of age at onset or of disease severity through generations. Most subjects presented with jerky, myoclonic-like dystonic movements of the neck or shoulders. DYT13-PTD is an autosomal dominant disease, with incomplete penetrance (58%). Clinical presentation and age at onset were more variable than in DYT1-PTD, and the neck was involved in most of those affected. Moreover, the individuals with generalised dystonia were not severely disabled and were able to lead independent lives. To date, this is the only family with DYT13-PTD.     

Intrafamilial phenotypic variability of the DYT1 dystonia: from asymptomatic TOR1A gene carrier status to dystonic storm.

When primary torsion dystonia is caused by a GAG deletion in the TOR1A gene (DYT1 dystonia), it typically presents with an early-onset dystonia involving distal limbs, subsequently spreading to a generalized dystonia. We describe a large family with an unusually broad variability in the clinical features of their dystonia both with regard to severity and age of onset. The proband of this family succumbed in his second decade to malignant generalized dystonia, whereas other family members carrying the same mutation are either asymptomatic or display dystonia that may be focal, segmental, multifocal, or generalized in distribution. One family member had onset of her dystonia at age 64 years, probably the oldest reported in genetically confirmed DYT1 dystonia. We conclude that marked phenotypic heterogeneity characterizes some families with DYT1 dystonia, suggesting a role for genetic, environmental, or other modifiers. These findings have implications for genetic testing and counseling.     

DYT1 mutation in a cohort of Taiwanese primary dystonias

To investigate the DYT1 gene mutation in Chinese ethnic, we examined a series of 200 patients with primary dystonias (11 familial and 189 sporadic), 53 of their asymptomatic relatives, 97 patients with familial or early-onset parkinsonism, and 200 healthy subjects. The GAG deletion at codon 946 was only found in three sporadic dystonia patients and seven of their asymptomatic familial members. The frequency of GAG deletion was 1.5% in dystonia patients, and was 6.7% in early-onset dystonias (< or = 26 years). We conclude that DYT1 mutation is a minor cause of primary dystonias in a cohort of Taiwanese population.