Scoring Algorithm-Based Genomic Testing in Dystonia: A Prospective Validation Study.

BACKGROUND: Despite the established value of genomic testing strategies, practice guidelines for their use do not exist in many indications. OBJECTIVES: We sought to validate a recently introduced scoring algorithm for dystonia, predicting the diagnostic utility of whole-exome sequencing (WES) based on individual phenotypic aspects (age-at-onset, body distribution, presenting comorbidity). METHODS: We prospectively enrolled a set of 209 dystonia-affected families and obtained summary scores (0-5 points) according to the algorithm. Singleton (N = 146), duo (N = 11), and trio (N = 52) WES data were generated to identify genetic diagnoses. RESULTS: Diagnostic yield was highest (51%) among individuals with a summary score of 5, corresponding to a manifestation of early-onset segmental or generalized dystonia with coexisting non-movement disorder-related neurological symptoms. Sensitivity and specificity at the previously suggested threshold for implementation of WES (3 points) was 96% and 52%, with area under the curve of 0.81. CONCLUSIONS: The algorithm is a useful predictive tool and could be integrated into dystonia routine diagnostic protocols. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson Movement Disorder Society.

The neurological and neuropsychiatric spectrum of adults with late-treated phenylketonuria.

INTRODUCTION: Phenylketonuria (PKU) is a rare, treatable inborn error of metabolism with frequent neurological and neuropsychiatric complications, especially in undiagnosed or insufficiently treated individuals. Given the wide range of clinical presentations and the importance of treatment implications, we here delineate the neurological and neuropsychiatric symptom spectrum in a large cohort of previously unreported adults with late-treated PKU. METHODS: We consecutively evaluated late-treated PKU cases and pooled clinical and paraclinical data, including video-material, from three centers with expertise in complex movement disorders, inborn errors of metabolism and pediatrics. RESULTS: 26 individuals were included (10 females, median age 52 years). Developmental delay and intellectual disability were omnipresent with severe impairment of expressive communication noted in 50% of cases. Movement disorders were prevalent (77%), including tremor (38%, mostly postural), stereotypies (38%), and tics (19%). One case had neurodegenerative levodopa-responsive parkinsonism. Mild ataxia was noted in 54% of cases and 31% had a history of seizures. Neuropsychiatric characteristics included obsessive-compulsive (35%) and self-injurious behaviors (31%), anxiety (27%), depression (19%) and features compatible with those observed in individuals with autism spectrum disorder (19%). Neuroimaging revealed mild white matter changes. Adherence to dietary treatment was inconsistent in the majority of cases, particularly throughout adolescence. CONCLUSION: A history of movement disorders, particularly tremor, stereotypies and tics, in the presence of developmental delay, intellectual disability and neuropsychiatric features, such as obsessive-compulsive and self-injurious behaviors in adults should prompt the diagnostic consideration of PKU. Initiation and adherence to (dietary) treatment can ameliorate the severity of these symptoms.

Clinically relevant copy-number variants in exome sequencing data of patients with dystonia.

INTRODUCTION: Next-generation sequencing is now used on a routine basis for molecular testing but studies on copy-number variant (CNV) detection from next-generation sequencing data are underrepresented. Utilizing an existing whole-exome sequencing (WES) dataset, we sought to investigate the contribution of rare CNVs to the genetic causality of dystonia. METHODS: The CNV read-depth analysis tool ExomeDepth was applied to the exome sequences of 953 unrelated patients with dystonia (600 with isolated dystonia and 353 with combined dystonia; 33% with additional neurological involvement). We prioritized rare CNVs that affected known disease genes and/or were known to be associated with defined microdeletion/microduplication syndromes. Pathogenicity assessment of CNVs was based on recently published standards of the American College of Medical Genetics and Genomics and the Clinical Genome Resource. RESULTS: We identified pathogenic or likely pathogenic CNVs in 14 of 953 patients (1.5%). Of the 14 different CNVs, 12 were deletions and 2 were duplications, ranging in predicted size from 124bp to 17 Mb. Within the deletion intervals, BRPF1, CHD8, DJ1, EFTUD2, FGF14, GCH1, PANK2, SGCE, UBE3A, VPS16, WARS2, and WDR45 were determined as the most clinically relevant genes. The duplications involved chromosomal regions 6q21-q22 and 15q11-q13. CNV analysis increased the diagnostic yield in the total cohort from 18.4% to 19.8%, as compared to the assessment of single-nucleotide variants and small insertions and deletions alone. CONCLUSIONS: WES-based CNV analysis in dystonia is feasible, increases the diagnostic yield, and should be combined with the assessment of single-nucleotide variants and small insertions and deletions.

Whole exome sequencing identifies a homozygous POLG2 missense variant in an adult patient presenting with optic atrophy, movement disorders, premature ovarian failure and mitochondrial DNA depletion.

POLG2 associated disorders belong to the group of mitochondrial DNA (mtDNA) diseases and present with a heterogeneous clinical spectrum, various age of onset, and disease severity. We report a 39-year old female presenting with childhood-onset and progressive neuroophthalmic manifestation with optic atrophy, mixed polyneuropathy, spinal and cerebellar ataxia and generalized chorea associated with mtDNA depletion. Whole-exome sequencing identified an ultra-rare homozygous missense mutation located at Chr17: 062474101-C > A (p.Asp433Tyr) in nuclear POLG2 gene encoding PolγB, an accessory subunits of mitochondrial polymerase γ responsible for mtDNA replication. The healthy parents and 2 sisters of the patient were heterozygous for the variant. To our best knowledge, this is the first case of homozygous variant in the POLG2 gene resulting in mitochondrial depletion syndrome in an adult patient and its clinical manifestations extend the clinical spectrum of POLG2 associated diseases.