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 the Atypical Parkinsonism Genes: MDSGene Systematic Review.

This Movement Disorder Society Genetic mutation database Systematic Review focuses on monogenic atypical parkinsonism with mutations in the ATP13A2, DCTN1, DNAJC6, FBXO7, SYNJ1, and VPS13C genes. We screened 673 citations and extracted genotypic and phenotypic data for 140 patients (73 families) from 77 publications. In an exploratory fashion, we applied an automated classification procedure via an ensemble of bootstrap-aggregated ("bagged") decision trees to distinguish these 6 forms of monogenic atypical parkinsonism and found a high accuracy of 86.5% (95%CI, 86.3%-86.7%) based on the following 10 clinical variables: age at onset, spasticity and pyramidal signs, hypoventilation, decreased body weight, minimyoclonus, vertical gaze palsy, autonomic symptoms, other nonmotor symptoms, levodopa response quantification, and cognitive decline. Comparing monogenic atypical with monogenic typical parkinsonism using 2063 data sets from Movement Disorder Society Genetic mutation database on patients with SNCA, LRRK2, VPS35, Parkin, PINK1, and DJ-1 mutations, the age at onset was earlier in monogenic atypical parkinsonism (24 vs 40 years; P = 1.2647 × 10-12) and levodopa response less favorable than in patients with monogenic typical presentations (49% vs 93%). In addition, we compared monogenic to nonmonogenic atypical parkinsonism using data from 362 patients with progressive supranuclear gaze palsy, corticobasal degeneration, multiple system atrophy, or frontotemporal lobar degeneration. Although these conditions share many clinical features with the monogenic atypical forms, they can typically be distinguished based on their later median age at onset (64 years; IQR, 57-70 years). In conclusion, age at onset, presence of specific signs, and degree of levodopa response inform differential diagnostic considerations and genetic testing indications in atypical forms of parkinsonism. © 2021 International Parkinson and Movement Disorder Society.

Expanding Data Collection for the MDSGene Database: X-linked Dystonia-Parkinsonism as Use Case Example.

MDSGene is an online database on movement disorders that collates genetic and clinical knowledge using a standardized published literature abstraction strategy. This review is dedicated to X-linked dystonia-parkinsonism (XDP). We screened 233 citations and curated phenotypic and genotypic data for 414 cases. To reduce data missingness, we (1) contacted authors and engaged the research community to provide additional clinical and genetic information, and (2) revisited previously unpublished data from a cohort of XDP patients seen at our institution. Using these approaches, we expanded the cohort to 577 cases and increased information available for important clinical and genetic features such as age at onset, initial manifestation, predominant motor symptoms, functional impairments, and repeat size information. We established the use of mining unpublished data to expand the MDSGene workflow and present an up-to-date description of the phenomenology of XDP using an extensive collection of previously reported and unreported data. © 2020 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Therapies for Genetic Forms of Parkinson's Disease: Systematic Literature Review.

Parkinson's disease (PD) is a disabling neurological condition characterized by the loss of dopaminergic neurons. Currently, the treatment for PD is symptomatic and compensates for the endogenous loss of dopamine production. In cases where the pharmacological therapy is only partly beneficial or results in major wearing-off complications, surgical interventions such as deep brain stimulation may be an alternative treatment. The disease cause often remains unknown, but in some patients, a monogenic cause can be identified. Mutations in at least six genes, LRRK2, SNCA, and VPS35 (dominant forms) or Parkin/PRKN, PINK1, and DJ1/PARK7 (recessive forms) have been unequivocally linked to PD pathogenesis. We here systematically screened 8,576 publications on these monogenic PD forms. We identified 2,226 mutation carriers from 456 papers. Levodopa was the most widely applied treatment; only 34 patients were indicated to be untreated at the time of reporting. Notably, detailed treatment data was rarely mentioned including response quantification (good, moderate, minimal) in 951 and/or dose in 293 patients only. Based on available data, levodopa showed an overall good outcome, especially in LRRK2, VPS35, Parkin, and PINK1 mutation carriers ("good" response in 94.6-100%). Side effects of levodopa therapy were reported in ∼15-40%of levodopa-treated patients across genes with dyskinesias as the most frequent one. Non-levodopa medication was indicated to be administered to <200 patients with mainly good outcome. Only a few reports were available on outcomes of brain surgery. Here, most mutation carriers showed a good response. Importantly, none of the available treatments is harmful to one genetic form but effective in another one. In the light of different medication schemes, the progressive nature of PD, and side effects, an improvement of therapeutic options for PD is warranted including a treatabolome database to guide clinicians in treatment decisions. Further, novel disease-cause-modifying drugs are needed.

MDSGene: Closing Data Gaps in Genotype-Phenotype Correlations of Monogenic Parkinson's Disease.

Given the rapidly increasing number of reported movement disorder genes and clinical-genetic desciptions of mutation carriers, the International Parkinson's Disease and Movement Disorder Society Gene Database (MDSGene) initiative has been launched in 2016 and grown to become a large international project (http://www.mdsgene.org). MDSGene currently contains >1150 variants described in ∼5700 movement disorder patients in almost 1000 publications including monogenic forms of PD clinically resembling idiopathic (PARK-PINK1, PARK-Parkin, PARK-DJ-1, PARK-SNCA, PARK-VPS35, PARK-LRRK2), as well as of atypical PD (PARK-SYNJ1, PARK-DNAJC6, PARK-ATP13A2, PARK-FBXO7). Inclusion of genes is based on standardized published criteria for determining causation. Clinical and genetic information can be filtered according to demographic, clinical or genetic criteria and summary statistics are automatically generated by the MDSGene online tool. Despite MDSGene's novel approach and features, it also faces several challenges: i) The criteria for designating genes as causative will require further refinement, as well as time and support to replace the faulty list of 'PARKs'. ii) MDSGene has uncovered extensive clinical data gaps. iii) The quickly growing body of clinical and genetic data require a large number of experts worldwide posing logistic challenges. iv) MDSGene currently captures published data only, i.e., a small fraction of the available information on monogenic PD available. Thus, an important future aim is to extend MDSGene to unpublished cases in order to provide the broad data base to the PD community that is necessary to comprehensively inform genetic counseling, therapeutic approaches and clinical trials, as well as basic and clinical research studies in monogenic PD.

Nonmotor Signs in Genetic Forms of Parkinson's Disease.

Although only a minority (i.e., ~5%) of Parkinson's disease (PD) cases is due to well-defined genetic causes, important clues about the common, "idiopathic" PD (iPD) can be garnered from monogenic model diseases. Nonmotor signs (NMS) are also present in monogenic PD and reviewed in this chapter for the confirmed PD genes SNCA, LRRK2, VPS35, Parkin, PINK1, DJ-1, and the risk factor gene GBA. Within the context of the MDSGene database (www.mdsgene.org), we performed a systematic literature search and extracted information on cognitive decline, depression, psychotic signs and symptoms, autonomic signs and symptoms, anxiety, sleep disorder, and olfactory impairment. Notably, relatively few studies specifically addressed NMS in genetic PD and missing data ranged from 42% to 100%. Diagnostic criteria and examination methods were variable and cases differed widely for age at onset, disease duration, ethnicity, treatment, and comorbidity. Although in comparison to IPD, SNCA duplication carriers have the most similar course of disease, even for duplication carriers the frequencies of dementia, hallucinations, and depression seem higher than in IPD. Supporting the notion that LRRK2-linked PD has a similar course to iPD but is slightly more benign, the frequency of dementia is below that of iPD. For Parkin, the frequency of cognitive decline falls within the range of the general population above the age of 65 years. GBA mutations are associated with a distinct profile of cognitive impairment and a greater prevalence of depression. Despite the current data gaps, NMS should be considered as an important and often treatable concomitant feature of genetic parkinsonism.