Frequency of Hereditary and GBA1-Related Parkinsonism in Latin America: A Systematic Review and Meta-Analysis

BACKGROUND

Identifying hereditary parkinsonism is valuable for diagnosis, genetic counseling, patient prioritization in trials, and studying the disease for personalized therapies. However, most studies were conducted in Europeans, and limited data exist on admixed populations like those from Latin America.

OBJECTIVES

This study aims to assess the frequency and distribution of genetic parkinsonism in Latin America.

METHODS

We conducted a systematic review and meta-analysis of the frequency of parkinsonian syndromes associated with genetic pathogenic variants in Latin America. We defined hereditary parkinsonism as those caused by the genes outlined by the MDS Nomenclature of Genetic Movement Disorders and heterozygous carriers of GBA1 pathogenic variants. A systematic search was conducted in PubMed, Web of Science, Embase, and LILACS in August 2022. Researchers reviewed titles and abstracts, and disagreements were resolved by a third researcher. After this screening, five researchers reanalyzed the selection criteria and extracted information based on the full paper. The frequency for each parkinsonism-related gene was determined by the presence of pathogenic/likely pathogenic variants among screened patients. Cochran's Q and I2 tests were used to quantify heterogeneity. Meta-regression, publication bias tests, and sensitivity analysis regarding study quality were also used for LRRK2-, PRKN-, and GBA1-related papers.

RESULTS

We included 73 studies involving 3014 screened studies from 16 countries. Among 7668 Latin American patients, pathogenic variants were found in 19 different genes. The frequency of the pathogenic variants in LRRK2 was 1.38% (95% confidence interval [CI]: 0.52-2.57), PRKN was 1.16% (95% CI: 0.08-3.05), and GBA1 was 4.17% (95% CI: 2.57-6.08). For all meta-analysis, heterogeneity was high and publication bias tests were negative, except for PRKN, which was contradictory. Information on the number of pathogenic variants in the other genes is further presented in the text.

CONCLUSIONS

This study provides insights into hereditary and GBA1-related parkinsonism in Latin America. Lower GBA1 frequencies compared to European/North American cohorts may result from limited access to gene sequencing. Further research is vital for regional prevalence understanding, enabling personalized care and therapies. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

DYT‐TUBB4A ( DYT4 Dystonia): Clinical Anthology of 11 Cases and Systematized Review

Background

DYT‐TUBB4A, formerly known as DYT4, has not been comprehensively described as only one large family and three individual cases have been published. We have recently described an in depth genetic and protein structural analysis of eleven additional cases from four families with four new pathogenic variants. We aim to report on the phenomenology of these cases suffering from DYT‐TUBB4A and to perform a comprehensive review of the clinical presentation and treatment responses of all DYT‐TUBB4A cases reported in the literature.

Cases and Literature Review

The clinical picture was typically characterized by laryngeal dystonia (more than three quarters of all cases), associated with cervical dystonia, upper limb dystonia and frequent generalization. Extension of the dystonia to the lower limbs, creating the famous “hobby horse” gait, was present in more than 20% of cases (in only one of ours). Globus pallidus pars interna (GPi) deep brain stimulation (DBS), performed in 4 cases, led to a good improvement with greatest benefit in motoric and less benefit in laryngeal symptoms. Medical treatment was generally rather poorly effective, except some benefit from propranolol, tetrabenazine and alcohol intake.

Conclusion

Laryngeal involvement is a hallmark of DYT‐TUBB4A. Symptomatic treatment with GPi‐DBS led to the greatest benefit in motoric symptoms. Nevertheless, TUBB4A mutations remain an exceedingly rare cause of laryngeal or other isolated dystonia and regular screening of TUBB4A mutations for isolated dystonias has a very low yield.

Relationship of Genotype, Phenotype, and Treatment in Dopa-Responsive Dystonia: MDSGene Review

BACKGROUND

Pathogenic variants in 5 genes (GCH1, TH, PTS, SPR, and QDPR), involved in dopamine/tetrahydrobiopterin biosynthesis or recycling, have been linked to Dopa-responsive dystonia (DRD). Diagnosis and treatment are often delayed due to high between- and within-group variability.

OBJECTIVES

Comprehensively analyzed individual genotype, phenotype, treatment response, and biochemistry information.

METHODS

734 DRD patients and 151 asymptomatic GCH1 mutation carriers were included using an MDSGene systematic literature review and an automated classification approach to distinguish between different forms of monogenic DRDs.

RESULTS

Whereas dystonia, L-Dopa responsiveness, early age at onset, and diurnal fluctuations were identified as red flags, parkinsonism without dystonia was rarely reported (11%) and combined with dystonia in only 18% of patients. While sex was equally distributed in autosomal recessive DRD, there was female predominance in autosomal dominant DYT/PARK-GCH1 patients accompanied by a lower median age at onset and more dystonia in females compared to males. Accordingly, the majority of asymptomatic heterozygous GCH1 mutation carriers (>8 years of age) were males. Multiple other subgroup-specific characteristics were identified, showing high accuracy in the automated classification approach: Seizures and microcephaly were mostly seen in DYT/PARK-PTS, autonomic symptoms appeared commonly in DYT/PARK-TH and DYT/PARK-PTS, and sleep disorders and oculogyric crises in DYT/PARK-SPR. Biochemically, homovanillic acid and 5-hydroxyindoleacetic acid in CSF were reduced in most DRDs, but neopterin and biopterin were increased only in DYT/PARK-PTS and DYT/PARK-SPR. Hyperphenylalaninemia was seen in DYT/PARK-PTS, DYT/PARK-QDPR, and rarely reported in autosomal recessive DYT/PARK-GCH1.

CONCLUSIONS

Our indicators will help to specify diagnosis and accelerate start of treatment. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Genotype-Phenotype Relations for Isolated Dystonia Genes: MDSGene Systematic Review

This comprehensive MDSGene review is devoted to 7 genes - TOR1A, THAP1, GNAL, ANO3, PRKRA, KMT2B, and HPCA - mutations in which may cause isolated dystonia. It followed MDSGene's standardized data extraction protocol and screened a total of ~1200 citations. Phenotypic and genotypic data on ~1200 patients with 254 different mutations were curated and analyzed. There were differences regarding age at onset, site of onset, and distribution of symptoms across mutation carriers in all 7 genes. Although carriers of TOR1A, THAP1, PRKRA, KMT2B, or HPCA mutations mostly showed childhood and adolescent onset, patients with GNAL and ANO3 mutations often developed first symptoms in adulthood. GNAL and KMT2B mutation carriers frequently have 1 predominant site of onset, that is, the neck (GNAL) or the lower limbs (KMT2B), whereas site of onset in DYT-TOR1A, DYT-THAP1, DYT-ANO3, DYT-PRKRA, and DYT-HPCA was broader. However, in most DYT-THAP1 and DYT-ANO3 patients, dystonia first manifested in the upper half of the body (upper limb, neck, and craniofacial/laryngeal), whereas onset in DYT-TOR1A, DYT-PRKRA and DYT-HPCA was frequently observed in an extremity, including both upper and lower ones. For ANO3, a segmental/multifocal distribution was typical, whereas TOR1A, PRKRA, KMT2B, and HPCA mutation carriers commonly developed generalized dystonia. THAP1 mutation carriers presented with focal, segmental/multifocal, or generalized dystonia in almost equal proportions. GNAL mutation carriers rarely showed generalization. This review provides a comprehensive overview of the current knowledge of hereditary isolated dystonia. The data are also available in an online database (http://www.mdsgene.org), which additionally offers descriptive summary statistics. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

DYT-TUBB4A (DYT4 Dystonia): New Clinical and Genetic Observations

OBJECTIVE

To report 4 novel TUBB4A mutations leading to laryngeal and cervical dystonia with frequent generalization.

METHODS

We screened 4 families including a total of 11 definitely affected members with a clinical picture resembling the original description.

RESULTS

Four novel variants in the TUBB4A gene have been identified: D295N, R46M, Q424H, and R121W. In silico modeling showed that all variants have characteristics similar to R2G. The variants segregate with the disease in 3 of the families with evidence of incomplete penetrance in 2 of them. All 4 variants would be classified as likely pathogenic. The clinical picture particularly included laryngeal dystonia (often the site of onset), associated with cervical and upper limb dystonia and frequent generalization. Laryngeal dystonia was extremely prevalent (>90%) both in the original cases and in this case series. The hobby horse gait was evident in only 1 patient in this case series.

CONCLUSIONS

Our interpretation is that laryngeal involvement is a hallmark feature of DYT-TUBB4A. Nevertheless, TUBB4A mutations remain an exceedingly rare cause of laryngeal or other isolated dystonia.

Understanding dystonia: diagnostic issues and how to overcome them

ABSTRACT The diagnosis and treatment of dystonia are challenging. This is likely due to gaps in the complete understanding of its pathophysiology, lack of animal models for translational studies, absence of a consistent pathological substrate and highly variable phenotypes and genotypes. The aim of this review article is to provide an overview of the clinical, neurophysiological and genetic features of dystonia that can help in the identification of this movement disorder, as well as in the differential diagnosis of the main forms of genetic dystonia. The variation of penetrance, age of onset, and topographic distribution of the disease in carriers of the same genetic mutation indicates that other factors – either genetic or environmental – might be involved in the development of symptoms. The growing knowledge of cell dysfunction in mutants may give insights into more effective therapeutic targets.

Altered activation of protein kinase PKR and enhanced apoptosis in dystonia cells carrying a mutation in PKR activator protein PACT

PACT is a stress-modulated activator of the interferon-induced double-stranded RNA-activated protein kinase (PKR). Stress-induced phosphorylation of PACT is essential for PACT's association with PKR leading to PKR activation. PKR activation leads to phosphorylation of translation initiation factor eIF2α inhibition of protein synthesis and apoptosis. A recessively inherited form of early-onset dystonia DYT16 has been recently identified to arise due to a homozygous missense mutation P222L in PACT. To examine if the mutant P222L protein alters the stress-response pathway, we examined the ability of mutant P222L to interact with and activate PKR. Our results indicate that the substitution mutant P222L activates PKR more robustly and for longer duration albeit with slower kinetics in response to the endoplasmic reticulum stress. In addition, the affinity of PACT-PACT and PACT-PKR interactions is enhanced in dystonia patient lymphoblasts, thereby leading to intensified PKR activation and enhanced cellular death. P222L mutation also changes the affinity of PACT-TRBP interaction after cellular stress, thereby offering a mechanism for the delayed PKR activation in response to stress. Our results demonstrate the impact of a dystonia-causing substitution mutation on stress-induced cellular apoptosis.

Sensory tricks in focal dystonia and hemifacial spasm

BACKGROUND AND PURPOSE

Sensory tricks are sensory, often but not exclusively tactile, stimuli usually in the body part affected by the movement disorder that produce a meaningful alleviation of dystonia. The frequency and clinical features of sensory tricks in different types of dystonia are poorly studied in the literature. There is no information regarding the presence of a similar phenomenon in HFS.

METHODS

We enrolled consecutive patients who had the diagnosis of HFS (26) or the following types of dystonia: cervical dystonia (CD; 21); blepharospasm (BS; 20); and writer's cramp (WC; 10). Patients underwent a structured interview to assess the following items related to sensory trick: presence, type and effectiveness. Statistical analysis used the Verisimilitude Reason test and the significance level was set at 5%.

RESULTS

Sensory trick was more frequent in the CD group (81%) when compared with HFS (38.5%; P=0.004) and WC (20%; P=0.001), but there was no statistical difference from the frequency in BS patients (55%; P=0.078). The most common sensory tricks were facial massage (60%) in HFS; to touch the head with the hands (35.3% in CD); to touch the upper eyelid with the index finger and thumb (81.8%) in BS; and to touch the hand with the contralateral hand (100%) in WC.

CONCLUSIONS

Sensory tricks are common in all types of focal dystonia herein studied, although they are more frequent in CD. Patients with HFS also often display improvement of the movement disorder with tactile stimulation.

DYT16: the original cases

OBJECTIVE

DYT16 is an autosomal recessive dystonia-parkinsonism due to putative mutations at PRKRA gene. The aim of this study was to describe clinical features providing video documentation of patients with DYT16 dystonia.

METHODS

We examined and videotaped all homozygous carriers of the DYT16 gene.

RESULTS

We identified two phenotypes, generalised dystonia and dystonia-parkinsonism non-responsive to levo-dopa, with three patients belonging to each of the groups. There was inter-individual and intra-family phenotypic heterogeneity.

CONCLUSIONS

DYT16 is a rare autosomal recessive dystonia characterised by generalised dystonia or dystonia-parkinsonism. Patients are refractory to pharmacological therapy.

New algorithm for the diagnosis of hereditary dystonia

Taking into account the crescent interest in the field of dystonia genetics, we have organized a didactic and fast algorithm to diagnose the main forms of hereditary dystonias. The key branch of this algorithm is pointed to dystonia classification in primary, plus, or paroxysmal. The specific characteristics of each syndrome will reveal the diagnosis.

Juvenile parkinsonism: a heterogeneous entity

We studied the clinical features, laboratory investigation, management and natural history of a cohort of patients with Juvenile Parkinsonism (JP), seen at a tertiary referral centre. JP was defined as Parkinsonism with onset at age 20 years or less. Six patients (five male, one female) entered the study. The mean age at onset of Parkinsonism was 12.5 years (range 7-19) and the mean follow-up time was 49.3 months (range 40-57). Bradykinesia, rigidity, and postural instability were observed in all patients and five subjects had tremor. Dystonia was present in four subjects. Other clinical features were dementia (five subjects), supranuclear ophthalmoparesis (five subjects), seizures (three subjects), multifocal myoclonus (one subject), decreased deep reflexes (one subject), pyramidal signs (one subject). Family history of Parkinson's disease (PD) was positive in one subject. Work-up for Wilson's disease was negative in all patients. Neuroimaging studies showed cortical atrophy in two subjects and mild brainstem atrophy in two others. Sea-blue histiocytes were found in one subject. L-dopa improved the Parkinsonism in all subjects but four rapidly developed fluctuations and dyskinesias, requiring, in one, stereotaxic surgery. After a mean disease duration of 6.5 years, five subjects require assistance for performance of all daily activities. JP is a heterogeneous clinical entity. In the majority of patients, no underlying cause is identified. The unusual clinical features suggest most subjects have a CNS degenerative disease distinct from PD. There is, however, evidence suggesting that PD may rarely cause JP. Gangliosidosis is another cause of L-dopa-responsive JP. Regardless of the cause, in the present study JP displays an aggressive and rapidly progressive course in most patients.