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BACKGROUND: Pathogenic variants in KITLG, a crucial protein involved in pigmentation and neural crest cell migration, cause non-syndromic hearing loss, Waardenburg syndrome type 2, familial progressive hyperpigmentation and familial progressive hyper- and hypopigmentation, all of which are inherited in an autosomal dominant manner. OBJECTIVES: To describe the genotypic and clinical spectrum of biallelic KITLG-variants. METHODS: We used a genotype-first approach through the GeneMatcher data sharing platform to collect individuals with biallelic KITLG variants and reviewed the literature for overlapping reports. RESULTS: We describe the first case series with biallelic KITLG variants; we expand the known hypomelanosis spectrum to include a 'sock-and-glove-like', symmetric distribution, progressive repigmentation and generalized hypomelanosis. We speculate that KITLG biallelic loss-of-function variants cause generalized hypomelanosis, whilst variants with residual function lead to a variable auditory-pigmentary disorder mostly reminiscent of Waardenburg syndrome type 2 or piebaldism. CONCLUSIONS: We provide consolidating evidence that biallelic KITLG variants cause a distinct auditory-pigmentary disorder. We evidence a significant clinical variability, similar to the one previously observed in KIT-related piebaldism.

BackgroundPatients with Parkinson’s disease (PD) have variable disease progression. More accurate prediction of progression could improve clinical trial design. Although some variance in clinical progression can be predicted by age at onset and phenotype, we hypothesise that this can be improved by blood biomarkers.ObjectiveTo determine if serum neurofilament light (NfL) is a useful biomarker for prognostic modelling in PD.MethodsWe evaluated the relationship between serum NfL and baseline and longitudinal clinical measures as well as patients’ genetic (GBA and APOE) status in a large clinical dataset. We classified patients as having a favourable or an unfavourable outcome based on a previously validated model and explored whether serum NfL could distinguish prognostic phenotypes. We compared NfL with baseline candidate predictor variables and studied the combination of clinical, serum and genetic data.ResultsSerum NfL was associated with patients’ cognitive status at baseline. Baseline NfL was associated with the progression of motor and functional impairment and with increased mortality (Survival HR 1.85, CI: 1.03-3.33, p=0.04). Baseline NfL levels predicted unfavourable progression to a similar extent as previously validated clinical predictors (AUC: 0.74 vs 0.78, p=0.22). The combination of clinical, genetic and biomarker data produced a strong predication of unfavourable outcomes as compared to age and gender alone (AUC: 0.71-age/gender vs 0.83-ALL p = 0.0076)ConclusionsBaseline serum NfL provides an objective measure of neurodegeneration in PD patients. Clinical trials of disease-modifying therapies might usefully stratify patients according using clinical, genetic and NfL status at the time of recruitment.

ObjectiveTo investigate the effectiveness of targeted next-generation sequencing (NGS) panels in achieving a molecular diagnosis in Charcot-Marie-Tooth disease (CMT) and related disorders in a clinical setting.MethodsWe prospectively enrolled 220 patients from 2 tertiary referral centers, one in London, United Kingdom (n = 120), and one in Iowa (n = 100), in whom a targeted CMT NGS panel had been requested as a diagnostic test.PMP22duplication/deletion was previously excluded in demyelinating cases. We reviewed the genetic and clinical data upon completion of the diagnostic process.ResultsAfter targeted NGS sequencing, a definite molecular diagnosis, defined as a pathogenic or likely pathogenic variant, was reached in 30% of cases (n = 67). The diagnostic rate was similar in London (32%) and Iowa (29%). Variants of unknown significance were found in an additional 33% of cases. Mutations inGJB1,MFN2, andMPZaccounted for 39% of cases that received genetic confirmation, while the remainder of positive cases had mutations in diverse genes, includingSH3TC2,GDAP1,IGHMBP2,LRSAM1,FDG4, andGARS, and another 12 less common genes. Copy number changes inPMP22,MPZ,MFN2,SH3TC2, andFDG4were also accurately detected. A definite genetic diagnosis was more likely in cases with an early onset, a positive family history of neuropathy or consanguinity, and a demyelinating neuropathy.ConclusionsNGS panels are effective tools in the diagnosis of CMT, leading to genetic confirmation in one-third of cases negative forPMP22duplication/deletion, thus highlighting how rarer and previously undiagnosed subtypes represent a relevant part of the genetic landscape of CMT.

Objective To develop a patient/care-giver reported scale capable of easily and reliably assessing functional disability in 4 repeat tauopathies (4RTs). Background 4R tauopathies including progressive supranuclear palsy, corticobasal degeneration and a subset of frontotemporal dementias manifest a range of overlapping clinical phenotypes. No available rating scale is capable of evaluating the functional impact of these complex disorders. Methods A multi-staged modified Delphi process was used to propose, evaluate and rank potential scale items providing content validity ratios. Staged cognitive pretesting involving input from examiners, patients and caregivers was followed by validation testing in patients participating in the 4R Tauopathy Neuroimaging Initiative or the PROgressive Supranuclear Palsy CorTico-Basal Syndrome MSA Longitudinal Study. Clinimetric properties were examined using classical test theory and item response methods, assessing data quality, reliability, construct validity, convergent validity and known-group validity. Results The resultant Cortical Basal ganglia Functional Scale (CBFS) included questions on Motor Experiences in Daily Living (14 items) and Non-Motor Experiences of Daily Living (17 items). Reliability was acceptable for internal consistency, test-retest stability, item discrimination, item-scaling thresholds and item-fit. Examination of construct validity revealed a parsimonious two-factor solution, and concurrent validity demonstrated significant correlations between the CBFS and other measures of disease severity and functional impairment. The CBFS significantly discriminated between all diagnostic groups and controls (all AUCs>90). The CBFS scores demonstrated sensitivity to change over a 12 month follow-up in patients with probable 4RTs. Conclusions The CBFS is a patient/care-giver reported outcome measure with excellent clinimetric properties that captures disability correlated with motor, cognitive and psychiatric impairments.

We present a patient with progressive spastic ataxia, with dystonia and anarthria undiagnosed until detailed genetic analysis revealed an MPAN mutation. Highlighting the worldwide MPAN distribution, a 30 year history of absent diagnosis and the impact and cost saving of an early but detailed genetic analysis in complex progressive movement disorders, particularly the anarthric NBIA group.

X-linked Charcot-Marie-Tooth disease (CMTX) is a clinically heterogeneous hereditary motor and sensory neuropathy with X-linked transmission. Common clinical manifestations of CMTX, as in other forms of Charcot-Marie-Tooth disease (CMT), are distal muscle wasting and weakness, hyporeflexia, distal sensory disturbance, and foot deformities. Motor nerve conduction velocity is reduced. In male patients it is often less than 38 m/s in the median nerve (a value often used to distinguish between "demyelinating" and "axonal" forms of CMT), but in female patients conduction velocity may be faster than this or normal. Mutations in the connexin32 (gap junction protein beta 1 (GJB1)) gene are responsible for the majority of CMTX cases. This report describes six British CMTX families with six novel mutations (four missense, one nonsense, and one frame shift) of the GJB1 gene. Affected members in these six families had typical signs of CMT but in some affected members of three families there was additional central nervous system involvement or deafness in the absence of any other explanation other than CMT.

Background: Charcot-Marie-Tooth disease (CMT) is the most common inherited neuromuscular disorder and is characterized by significant clinical and genetic heterogeneity. Recently, mutations in both the small heat shock protein 27 ( HSP27 or HSPB1 ) and 22 ( HSP22 or HSPB8 ) genes have been reported to cause autosomal dominant CMT with minimal sensory involvement (CMT 2F/CMT2L) and autosomal dominant distal hereditary motor neuropathy type II (dHMN II). Methods: We analyzed the HSPB1 and HSPB8 genes in a large clinically well-characterized series of dHMN and CMT type 2 (CMT2) cases and families using linkage analysis and direct sequencing of these genes. Results: We identified a novel homozygous mutation in the α-crystallin domain of HSPB1 segregating in an autosomal recessive fashion in a family with distal HMN/CMT2. A further four heterozygous HSPB1 mutations were identified in four autosomal dominant families dHMN/CMT2, and two sporadic cases were identified with probable de novo mutations. In the autosomal dominant and autosomal recessive families, there were no clinical sensory findings, but reduced sural nerve action potential amplitudes were found in some affected individuals, indicating that long sensory axons are mildly affected in this predominantly motor disorder. Conclusions: This extends the clinical and electrophysiologic spectrum of HSPB1 mutations and identifies four unreported dominant HSPB1 mutations and the first family where the HSPB1 mutation acts in a recessive way to cause distal HMN.

The authors describe a patient with hypoprebetalipoproteinemia, acanthocytosis, retinitis pigmentosa, and pallidal degeneration (HARP) who has two compound heterozygote mutations of the PANK2 gene. IVS4–1 G>T segregates with the lipid and erythrocyte changes in the mother and sister. No other family members have the lipid, erythrocyte, or clinical abnormalities. The father and two brothers are heterozygous for Met327Thr. One other mutation has been found in this PANK2 region associated with the HARP phenotype, suggesting a local genotype effect.

Many genes implicated in familial Parkinson disease (PD) code for proteins with mitochondrial function.1 Several of these genes, including PINK1 and PARK2, are involved in mitophagy, a mitochondrial quality control pathway.2 We describe a family with 3 members affected by autosomal dominant optic atrophy in which 2 affected members also developed PD.

Neurodegeneration with brain iron accumulation (NBIA) is a group of disorders characterized by dystonia, parkinsonism and spasticity. Iron accumulates in the basal ganglia and may be accompanied by Lewy bodies, axonal swellings and hyperphosphorylated tau depending on NBIA subtype. Mutations in 10 genes have been associated with NBIA that include Ceruloplasmin (Cp) and ferritin light chain (FTL), both directly involved in iron homeostasis, as well as Pantothenate Kinase 2 (PANK2), Phospholipase A2 group 6 (PLA2G6), Fatty acid hydroxylase 2 (FA2H), Coenzyme A synthase (COASY), C 19orf12, WDR 45 and DCAF 17 (C 2orf37). These genes are involved in seemingly unrelated cellular pathways, such as lipid metabolism, Coenzyme A synthesis and autophagy. A greater understanding of the cellular pathways that link these genes and the disease mechanisms leading to iron dyshomeostasis is needed. Additionally, the major overlap seen between NBIA and more common neurodegenerative diseases may highlight conserved disease processes. In this review, we will discuss clinical and pathological findings for each NBIA‐related gene, discuss proposed disease mechanisms such as mitochondrial health, oxidative damage, autophagy/mitophagy and iron homeostasis, and speculate the potential overlap between NBIA subtypes.

Arthrogryposis is a heterogeneous birth defect characterized by limitation of movement at multiple joints. One in 3,000 infants is born with arthrogryposis, and at least a third of these cases have a genetic cause. Four distinct types of X-linked arthrogryposis have been reported, and a severe lethal form recently was mapped to Xpll.3-qll.2. We now report an extended family affected with a novel variant of X-linked arthrogryposis that involves only the lower limbs. Linkage analysis with polymorphic DNA markers maps the disease locus in this unique family to the long arm of the human X chromosome between DXS1220 and DXS1205 in Xq23-27.

Neuropathology has been the key to understanding the aetiology of many neurological disorders such as Alzheimer's disease, Parkinson's disease, frontotemporal degeneration and cerebellar ataxias. Dystonia shares many clinical features with these conditions but research in general, has been unrewarding in providing information on disease processes. Neuropathological studies are few in number and only limited morphological abnormalities have been described. In the genetic literature, dystonia loci are represented as DYT and are assigned ascending numerals chronologically as they are identified. This review will concentrate on the neuropathology of primary pure dystonia, focusing on DYT1 and DYT6 and the correlation between clinical and genetic findings. Research in this area is incomplete and confounded by the rarity of post mortem brain tissue. However, recent findings, indicating a direct interaction between the torsinA (TOR1A) gene responsible for DYT1 and the thanatos-associated domain-containing apoptosis-associated protein 1 (THAP1) gene responsible for DYT6, have important implications in understanding these two entities and also for other members of this group of disorders.

Aims: Mutations in the pantothenate kinase 2 gene (PANK2) are responsible for the most common type of neurodegeneration with brain iron accumulation (NBIA), known as pantothenate kinase-associated neurodegeneration (PKAN). Historically, NBIA is considered a synucleinopathy with numerous reports of NBIA cases with Lewy bodies and Lewy neurites and some cases reporting additional abnormal tau accumulation. However, clinicopathological correlations in genetically proven PKAN cases are rare. We describe the clinical, genetic and neuropathological features of three unrelated PKAN cases. Methods: All three cases were genetically screened for the PANK2 gene mutations using standard Sanger polymerase chain reaction sequencing. A detailed neuropathological assessment of the three cases was performed using histochemical and immunohistochemical preparations. Results: All cases had classical axonal swellings and Perls' positive iron deposition in the basal ganglia. In contrast to neuroaxonal dystrophies due to mutation of the phospholipase A2, group VI (PLA2G6) gene, in which Lewy body pathology is widespread, no α-synuclein accumulation was detected in any of our PKAN cases. In one case (20-year-old male) there was significant tau pathology comprising neurofibrillary tangles and neuropil threads, with very subtle tau pathology in another case. Conclusions: These findings indicate that PKAN is not a synucleinopathy and, hence the cellular pathways implicated in this disease are unlikely to be relevant for the pathomechanism of Lewy body disorders.

Clinical characteristics Spinocerebellar ataxia type 11 (SCA11) is characterized by progressive cerebellar ataxia and abnormal eye signs (jerky pursuit, horizontal and vertical nystagmus). Pyramidal features are seen on occasion. Peripheral neuropathy and dystonia are rare. Six families have been reported to date, one each from the UK, Pakistan, France, Germany, Denmark, and China. Age of onset ranged from early childhood to the mid-40s. Life span is thought to be normal. Diagnosis/testing The diagnosis of spinocerebellar ataxia type 11 (SCA11) is established in a proband with a heterozygous pathogenic variant in TTBK2 identified by molecular genetic testing. Management Treatment of manifestations: Management is supportive; there are no known disease-modifying treatments to date. Physiotherapy and assessment for assistive devices for ambulation; occupational therapy, including home adaptations; speech and language therapy for dysarthria and dysphagia; ankle-foot orthotics if required and good foot care for those with neuropathy; treatment per ophthalmologist for vision issues; prism glasses may be helpful for diplopia. Surveillance: Annual neurologic evaluation; evaluations with physiotherapist, occupational therapist, speech and language therapist, and ophthalmologist as indicated. Genetic counseling SCA11 is inherited in an autosomal dominant manner. The proportion of SCA11 caused by de novo mutation is unknown. Each child of an individual with SCA11 has a 50% chance of inheriting the pathogenic variant. Prenatal diagnosis for at-risk pregnancies is possible if the diagnosis has been established by molecular genetic testing in an affected family member.

Pick's disease (PiD) is characterized by the deposition of tau protein as three-repeat tau Pick bodies, whereas progressive supranuclear palsy (PSP) involves the deposition of four-repeat tau neurofibrillary tangles. PSP is associated with the tau H1 haplotype. The authors investigated a possible association between PiD and the tau H1 or H2 haplotype. There was no difference between the tau H2 haplotype or H2H2 genotype frequency in PiD cases and control subjects. No tau mutations were identified in pathologically typical cases of PiD, with antibody 12-E8-negative Pick bodies.

Multiple system atrophy (MSA) is an unrelenting, sporadic, adult-onset, neurodegenerative disease of unknown aetiology. Its clinically progressive course is characterized by a variable combination of parkinsonism, cerebellar ataxia and/or autonomic dysfunction. Neuropathological examination often reveals gross abnormalities of the striatonigral and/or olivopontocerebellar systems, which upon microscopic examination are associated with severe neuronal loss, gliosis, myelin pallor and axonal degeneration. MSA is a member of a diverse group of neurodegenerative disorders termed α-synucleinopathies, due to the presence of abnormal α-synuclein positive cytoplasmic inclusions in oligodendrocytes, termed glial cytoplasmic inclusions. These are the hallmark neuropathological lesion of MSA and are thought to play a central role in the pathogenesis of the disease. In this review, neuropathological features of MSA are described in detail, along with recent advances in the pathophysiology and genetics of the disease. Our current knowledge of the expression and accumulation of α-synuclein, and efforts to model the disease in vitro and in vivo, are emphasized in this paper and have helped formulate a working hypothesis for the pathogenesis of MSA.

Autosomal recessive hereditary spastic paraplegia (ARHSP) with thin corpus callosum is a distinct and usually severe form of complex hereditary spastic paraplegia classified as SPG11. Recently mutations on SPG11 gene (KIAA1840), which is localized to chromosome 15q13-q15, were shown to cause the majority of SPG11 cases.We analysed the 40 coding exons of this gene in the probands from eight families with complex ARHSP, four of these families had a thin corpus callosum and two has mild thinning.Three families were identified with novel mutations in the SPG11 gene. One family was of Asian origin with a homozygous nonsense mutation and had a very severe phenotype but only very mild thinning of the corpus callosum. In the other two English families the parents were unrelated and the mutations were compound heterozygotes. In these two families the phenotype was mild and both probands had a thin corpus callosum.Given the probable mechanism of action of the mutations in the Spatacsin gene, we discuss the probable genotype phenotype correlations in these families. This study confirms the frequent occurrence of Spatacsin mutations in complex ARHSP with genotype phenotype effects and exposes the spectrum of clinical heterogeneity in SPG11.

To investigate and correlate the frequency and types of pupil abnormalities that are associated with hereditary peripheral neuropathy in a large cohort of patients prospectively examined. A prospective study between 1998 and 2007. Patients were enrolled and examined after being seen in the neurology clinic. Data were collected on demographics, family and medical history. Patients had eye and pupillography testing carried out as well as being neurologically and genetically investigated. A consecutive series of 131 cases of inherited peripheral neuropathy were seen and categorized into five groups: familial amyloid polyneuropathy (FAP), Charcot Marie Tooth disease (CMT), hereditary neuropathywith liability to pressure palsies (HNPP), Refsum's disease, and hereditary sensory and autonomic neuropathy. A number of unreported mutations were identified in these patient groups. Pupil abnormalities were common in the Refsum's group, with frequent abnormally small pupils. The inherited neuropathies commonly associated with autonomic abnormalities were frequently found to have developed bilateral Horner's syndrome, which was particularly prevalent in our FAP series. Abnormalities were rare in HNPP and CMT type 1, but CMT type 2 showed frequent and varied pupil defects. The results describe the pupil abnormalities that were frequently associated with the particular group of inherited neuropathy patients, but we could not predict the genetic defect or the neuropathy severity. This is the first study of the pupil abnormalities found in the inherited neuropathies and provides an overview of the frequency and type of defects seen in a large number of cases. This series along with the detailed tables will act as an important diagnostic aid in assessing these patients.

Mutations in the pantothenate kinase 2 gene (PANK2) are the cause of pantothenate kinase associated neurodegeneration (PKAN), an autosomal recessive (AR) disorder characterized by motor symptoms as such as dystonia or parkinsonism, mental retardation, retinitis pigmentosa and iron accumulation in the brain. As many neurodegenerative conditions have similar clinical features we screened a number of adult and childhood onset movement disorders for PANK2 mutation. This included cases with neurodegeneration and brain iron accumulation, corticobasal degeneartion, progressive supranuclear palsy (PSP), Parkinson's disease (PD), multiple system atropy, giant axonal neuropathy (GAN), neuroaxonal dystrophy (NAD), Guam dementia and HARP syndrome (pallido-pyramidal syndrome and hypoprebetalipoproteinemia, acanthocytosis, retinitis pigmentosa and pallidal degeneration). From our series of patients one patient with PKAN and a progressive severe dystonic syndrome, cerebellar ataxia, retinitis pigmentosa and eventual anarthria had a novel combination of two compound heterozygote mutations identified in the PANK2 gene, G-->A transition at base 1238 (G411R) and a C-->A transition at base 1184 (A395E). In the patient with HARP syndrome two compound heterozygote mutations (Met327Thr and IVS5-1 G to T) in the PANK2 gene were found. No other mutations were found in any of the other patient groups, suggesting that PANK2 mutations are not associated with the aetiology of these adult degenerative conditions and confirms the genetic heterogeneity in neurodegeneration with brain iron accumulation.

The ApoE-epsilon 4 allele is a predisposing factor for late onset Alzheimer's disease (AD), however it is neither necessary nor sufficient to cause the disease. A candidate for explaining part of the remaining genetic component is alpha 1-antichymotrypsin (AACT). In a case-control study we genotyped a polymorphism within the AACT gene to test for association with the disease. No allele of this gene showed an increased incidence among the population with AD compared with controls, even when taking ApoE genotype into account. This contrasts with the results of a recently published report. The mean age of onset was apparently lowered by the presence of the AACT AA genotype among ApoE-epsilon 4 bearers. If AACT genotype has an effect on risk for AD it may be predominantly amongst individuals with early onset AD.

Aims: To describe the clinical features and genetic findings in two families presenting with microcoria inherited as an autosomal dominant trait. Methods: Both affected and unaffected members of two families displaying familial microcoria were examined. Flash photography or infrared pupillography were used to assess pupils, and a full ophthalmic examination including visual acuity and field testing, refraction, biomicroscopy of anterior and posterior segments, and measurement of intraocular pressure were performed. DNA from the blood of affected and unaffected family members was investigated using standard markers to look for a possible gene defect in the chromosome 13q31–q32 region. Results: All affected members of both families had pinpoint pupils which responded normally to light and accommodation. None of these subjects exhibited any other ocular abnormality. The iris of affected members showed stromal thinning and apparent absence of the iris dilator muscle in the first family, but was smooth and lacked all trabecular structure in the second family. The microcoria was present at birth in the first family but developed progressively at a later age in the second family. Haplotype analysis suggested the gene defect is not located in the chromosome 13q31–q32 region in the first family but the evidence was not conclusive in the second family. Conclusion: Although both families presented with similar pupil abnormalities inherited as an autosomal dominant trait, they show important phenotypic and genotypic differences suggesting that this is a heterogeneous condition. The possible mechanisms underlying the microcoria are discussed.