Neuropathology of central nervous system involvement in TTR amyloidosis.

Hereditary transthyretin amyloidosis (ATTRv) is a systemic disease caused by the accumulation of misfolded transthyretin (TTR). It usually presents with an adult-onset progressive axonal peripheral neuropathy and cardiomyopathy. In the central nervous system (CNS), variant TTR is produced by the choroid plexus and accumulates in the leptomeninges. CNS symptoms have been increasingly recognized in this population, including transient focal neurological episodes and stroke, particularly in patients with the V30M mutation and longstanding disease. The prevalence, pathophysiology, and progression of CNS involvement remain to be clarified. The present work explores if there is a recognizable sequence of CNS TTR deposition in ATTRv. We studied the topographical and severity distribution of TTR deposition in 16 patients with ATTRv, aged 27-69 years and with a mean disease duration of 10.9 years (range: 3-29). Our results suggest that CNS pathological involvement in V30M ATTRv occurs early in the disease course, probably starting in pre-symptomatic phases, and follows a distinct sequence. Leptomeninges and subarachnoid meningeal vessels are affected earlier, then followed by perforating cortical vessels and subpial deposition, and finally by deposition in the subependymal and basal ganglia vessels near the ependymal lining. Brainstem and spinal cord show early and severe involvement, with amyloid subpial deposition already seen in initial stages. Despite massive superficial amyloid deposition, no parenchymal deposition outside subpial or subependymal regions was found. Additionally, vascular lesions or superficial cortical siderosis were not frequent. Future studies with more patients from different populations and TTR mutations will be important to confirm these findings. Defining stages of TTR pathology in the CNS may be useful to better understand pathogenic mechanisms leading to symptoms and to interpret neuroimaging biomarkers.

Intellectual disability genomics: current state, pitfalls and future challenges.

Intellectual disability (ID) can be caused by non-genetic and genetic factors, the latter being responsible for more than 1700 ID-related disorders. The broad ID phenotypic and genetic heterogeneity, as well as the difficulty in the establishment of the inheritance pattern, often result in a delay in the diagnosis. It has become apparent that massive parallel sequencing can overcome these difficulties. In this review we address: (i) ID genetic aetiology, (ii) clinical/medical settings testing, (iii) massive parallel sequencing, (iv) variant filtering and prioritization, (v) variant classification guidelines and functional studies, and (vi) ID diagnostic yield. Furthermore, the need for a constant update of the methodologies and functional tests, is essential. Thus, international collaborations, to gather expertise, data and resources through multidisciplinary contributions, are fundamental to keep track of the fast progress in ID gene discovery.

Adult polyglucosan body disease-an atypical compound heterozygous with a novel GBE1 mutation.

INTRODUCTION: Adult polyglucosan body disease (APBD) is an autosomal recessive leukodystrophy characterized by neurogenic bladder starting after 40 years old, spastic paraparesis and peripheral neuropathy. It is mainly resultant from the GBE1 homozygous p.Tyr329Ser (c.986A>C) mutation, especially in Ashkenazi-Jewish patients, although some cases of compound heterozygous have been reported. A genotype-phenotype correlation is not established, but atypical phenotypes have been described mainly in non-p.Tyr329Ser pathogenic variants. CASE REPORT: We describe an atypical case in a 62-year-old Portuguese woman, presenting the typical clinical triad of APBD plus prominent autonomic dysfunction, suggested by orthostatic hypotension and thermoregulatory dysfunction; she has compound heterozygous GBE1 mutations, namely, p.Asn541Asp (c.1621A>G) and p.Arg515Gly (c.1543C>G), the last one not yet reported in literature and whose pathogenicity was suggested by bioinformatics analysis and confirmed by sural nerve biopsy that showed intra-axonal polyglucosan bodies. DISCUSSION: Besides the report of a novel GBE1 mutation, this case also expands the phenotypic spectrum of this disorder, reinforcing autonomic dysfunction as a possible and prominent manifestation of APBD, mimicking autosomal dominant leukodystrophy with autonomic disease in some way. Therefore, we questioned a possible relationship between this genotype and the phenotype marked by dysautonomia. Additionally, we review previously reported cases of APBD in non-homozygous p.Tyr329Ser patients with atypical phenotypes.

LAMA2 gene mutation update: Toward a more comprehensive picture of the laminin-α2 variome and its related phenotypes.

Congenital muscular dystrophy type 1A (MDC1A) is one of the main subtypes of early-onset muscle disease, caused by disease-associated variants in the laminin-α2 (LAMA2) gene. MDC1A usually presents as a severe neonatal hypotonia and failure to thrive. Muscle weakness compromises normal motor development, leading to the inability to sit unsupported or to walk independently. The phenotype associated with LAMA2 defects has been expanded to include milder and atypical cases, being now collectively known as LAMA2-related muscular dystrophies (LAMA2-MD). Through an international multicenter collaborative effort, 61 new LAMA2 disease-associated variants were identified in 86 patients, representing the largest number of patients and new disease-causing variants in a single report. The collaborative variant collection was supported by the LOVD-powered LAMA2 gene variant database (https://www.LOVD.nl/LAMA2), updated as part of this work. As of December 2017, the database contains 486 unique LAMA2 variants (309 disease-associated), obtained from direct submissions and literature reports. Database content was systematically reviewed and further insights concerning LAMA2-MD are presented. We focus on the impact of missense changes, especially the c.2461A > C (p.Thr821Pro) variant and its association with late-onset LAMA2-MD. Finally, we report diagnostically challenging cases, highlighting the relevance of modern genetic analysis in the characterization of clinically heterogeneous muscle diseases.

The etiology of spontaneous intracerebralhemorrhage: Insights from a neuropathological series.

The etiology of intracerebral hemorrhage (ICH) is frequently undetermined. We aimed to assess the impact of the neuropathological study on the etiologic diagnosis of ICH. Patients with ICH admitted to a tertiary hospital in the last 14 years were identified, and histological samples of surgically-drained ICH were retrieved. Blinded from neuropathological results, a clinical etiology was hypothesized. Pathological samples were reviewed, and immunohistochemistry study for ß-amyloid was performed in all the cases where structural abnormalities were not identified. From 2002 - 2016, 113 patients with ICH underwent surgical drainage and had specimens taken for histology. The mean age was 51.6 years (SD = 19.2). Clinical and imaging data defined a presumable etiology in 47 patients (44.2%), including 30 patients with suspected structural pathology, 11 patients under anticoagulation, and 8 patients with probable hypertensive hemorrhage, while most had an undetermined etiology. Using neuropathological analysis, a definitive diagnosis was possible in 88.5% of the patients. Arteriovenous malformations (38.1%) and cavernous hemangiomas (16.8%) represented the most common findings. In 9.7%, the blood vessels showed cerebral amyloid angiopathy (CAA). The neuropathological study established a definite etiology in an additional 44.3% of patients other than only using the clinical and imaging data.
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Clinical, biochemical, molecular, and histological features of 65 Portuguese patients with mitochondrial disorders.

INTRODUCTION: Mitochondrial disorders display remarkable genetic and phenotypic heterogeneity. METHODS: We performed a retrospective analysis of the clinical, histological, biochemical, and genetic features of 65 patients with molecular diagnoses of mitochondrial disorders. RESULTS: The most common genetic diagnosis was a single large-scale mitochondrial DNA (mtDNA) deletion (41.5%), and the most frequent clinical phenotype was chronic progressive external ophthalmoplegia (CPEO). It occurred in 41.5% of all patients, primarily in those with mtDNA deletions. Histological signs of mitochondrial dysfunction were found in 73.8% of patients, and respiratory chain enzyme assay (RCEA) abnormalities were detected in 51.9%. CONCLUSIONS: This study confirms the high relative frequency of single large-scale deletions among mitochondrial disorders as well as its particular association with CPEO. Muscle histology seems to be particularly useful in older patients and those with mtDNA deletions, whereas RCEA might be more helpful in young children or individuals with mtDNA depletion. Muscle Nerve 56: 868-872, 2017.

DJ-1 linked parkinsonism (PARK7) is associated with Lewy body pathology.

Mutations in DJ-1 (encoded by PARK7) are a very rare cause of early-onset recessive Parkinson's disease. We describe a patient with early-onset parkinsonism, starting at the age of 22, with poor response to levodopa and additional features in progression (dystonia, pyramidal signs and dementia), who died when he was 49 years old. The neuropathological study showed severe substantia nigra and locus coeruleus neuronal loss, with diffuse Lewy body pathology (Lewy bodies, aberrant neurites, grain-like structures, spheroids and scattered glial pathology). Genetic analysis revealed a novel c.515T > A; p.L172Q mutation in the PARK7 gene. To evaluate the pathogenicity of this new mutation we explored DJ-1 expression levels in vitro showing a massive reduction in DJ-1 protein levels due to a highly unstable and rapidly degraded L172Q mutant. DJ-1 immunohistochemistry of brain tissue revealed no staining in our case. This is the first neuropathological report of a brain from DJ-1-linked parkinsonism that, although based on a single case study, suggests that DJ-1 mutations are causative of α-synucleinopathy. These results can help in the understanding of Parkinson's disease pathophysiology, promote research studies to increase the knowledge on the pathways involved in the neurodegeneration process, and pave the way for new therapeutic interventions.

Patterns of Microglial Cell Activation in Alzheimer Disease and Frontotemporal Lobar Degeneration.

AIMS: Microglia-driven neuroinflammation can play an important role in the pathophysiology of neurodegenerative disorders. In this study, we sought to characterize the distribution of microglial cell activation in 2 neurodegenerative dementias with distinct protein signatures, Alzheimer disease (AD) and frontotemporal lobar degeneration (FTLD) of the TDP subtype, and to determine if there was an anatomical correlation with the phenotypes most commonly associated with these conditions. METHODS: The distribution and extent of microglial cell activation was assessed semiquantitatively in the hippocampal formation, cortical gray matter, and subcortical white matter of CD68-immunostained sections of the frontal, temporal, parietal, and occipital cortices from 15 pathologically confirmed cases of AD, 13 cases of FTLD, and 18 controls. RESULTS: Significantly higher levels of microglial cell activation occurred in the subiculum in AD and FTLD than in controls. Additionally, AD had higher microglial activation in the CA1 and FTLD in the hippocampal white matter than the controls. Microglial activation was greater in the dentate gyrus molecular layer in AD than in FTLD. In the cortical regions, the 2 pathological groups differed only in frontal white matter, with the FTLD group showing higher microglial scores. FTLD showed higher microglial activation in the white matter compared to the respective gray matter in the entorhinal, temporal, and frontal regions. CONCLUSIONS: Our work expands the knowledge of the distribution and magnitude of microglial activation in these disorders. Additionally, we found some microglial circuit-specific patterns that could help to explain some of the clinical overlap between AD and FTLD-TDP, namely in memory deficits.

New massive parallel sequencing approach improves the genetic characterization of congenital myopathies.

Congenital myopathies (CMs) are a heterogeneous group of muscle diseases characterized by hypotonia, delayed motor skills and muscle weakness with onset during the first years of life. The diagnostic workup of CM is highly dependent on the interpretation of the muscle histology, where typical pathognomonic findings are suggestive of a CM but are not necessarily gene specific. Over 20 loci have been linked to these myopathies, including three exceptionally large genes (TTN, NEB and RYR1), which are a challenge for molecular diagnosis. We developed a new approach using massive parallel sequencing (MPS) technology to simultaneously analyze 20 genes linked to CMs. Assay design was based on the Ion AmpliSeq strategy and sequencing runs were performed on an Ion PGM system. A total of 12 patients were analyzed in this study. Among the 2534 variants detected, 14 pathogenic mutations were successfully identified in the DNM2, NEB, RYR1, SEPN1 and TTN genes. Most of these had not been documented and/or fully characterized, hereby contributing to expand the CM mutational spectrum. The utility of this approach was demonstrated by the identification of mutations in 70% of the patients included in this study, which is relevant for CMs especially considering its wide phenotypic and genetic heterogeneity.

CADASIL: MRI may be normal in the fourth decade of life - a case report.

Background Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) manifests by migraine with aura, cerebral ischemic events, mood disturbances and dementia. Brain MRI lesions typically precede the symptoms from 10 to 15 years and previous evidence showed all CADASIL patients above 35 years old have an abnormal MRI, supporting the clinical diagnosis. Case results We present a 37-year-old female patient with migraine without aura, a family history of CADASIL, normal brain 3-Tesla MRI and normal skin biopsy, even though a pathogenic NOTCH3 gene mutation (allele 2, exon 11, c.1672 C\gtT, p.Arg558Cys) was detected. Conclusions When CADASIL is strongly suspected, a normal brain MRI, even in the fourth decade of life, does not rule out the diagnosis and should not discourage the genetic test.

New splicing mutation in the choline kinase beta (CHKB) gene causing a muscular dystrophy detected by whole-exome sequencing.

Muscular dystrophies (MDs) are a group of hereditary muscle disorders that include two particularly heterogeneous subgroups: limb-girdle MD and congenital MD, linked to 52 different genes (seven common to both subgroups). Massive parallel sequencing technology may avoid the usual stepwise gene-by-gene analysis. We report the whole-exome sequencing (WES) analysis of a patient with childhood-onset progressive MD, also presenting mental retardation and dilated cardiomyopathy. Conventional sequencing had excluded eight candidate genes. WES of the trio (patient and parents) was performed using the ion proton sequencing system. Data analysis resorted to filtering steps using the GEMINI software revealed a novel silent variant in the choline kinase beta (CHKB) gene. Inspection of sequence alignments ultimately identified the causal variant (CHKB:c.1031+3G>C). This splice site mutation was confirmed using Sanger sequencing and its effect was further evaluated with gene expression analysis. On reassessment of the muscle biopsy, typical abnormal mitochondrial oxidative changes were observed. Mutations in CHKB have been shown to cause phosphatidylcholine deficiency in myofibers, causing a rare form of CMD (only 21 patients reported). Notwithstanding interpretative difficulties that need to be overcome before the integration of WES in the diagnostic workflow, this work corroborates its utility in solving cases from highly heterogeneous groups of diseases, in which conventional diagnostic approaches fail to provide a definitive diagnosis.

Acute hemorrhagic leukoencephalitis with severe brainstem and spinal cord involvement: MRI features with neuropathological confirmation.

Acute hemorrhagic leukoencephalitis (AHLE) is a rare and fulminant demyelinating disease considered to be the most severe form of acute disseminated encephalomyelitis (ADEM). A 70-year-old man was admitted to our emergency department (ED) after 1 week of unspecific abdominal symptoms and moderate fever in the first 3 days. Within the ED he developed a rapid onset coma and flaccid tetraparesis. Cerebrospinal fluid (CSF) analysis showed mild polymorphonuclear pleocytosis and magnetic resonance imaging (MRI) revealed supratentorial focal white matter lesions and diffuse involvement of the medulla and spinal cord. A presumptive diagnosis of ADEM was made and the patient was treated with corticosteroids followed by intravenous immunoglobulin. His neurological state did not improve and the MRI on day 8 after admission showed an increased number of lesions, mainly in the brainstem, with hemorrhagic foci. The patient died the following day and pathological features confirmed the diagnosis of AHLE. This is a unique presentation of a rare disease with detailed MRI characteristics and pathological confirmation. Although this condition is usually fatal, early recognition and aggressive therapeutic management can facilitate survival.

Two Compound Heterozygous Variants in SNX14 Cause Stereotypies and Dystonia in Autosomal Recessive Spinocerebellar Ataxia 20.

Autosomal Recessive Spinocerebellar Ataxia 20, SCAR20, is a rare condition characterized by intellectual disability, lack of speech, ataxia, coarse facies and macrocephaly, caused by SNX14 variants. While all cases described are due to homozygous variants that generally result in loss of protein, so far there are no other cases of reported compound heterozygous variants. Here we describe the first non-consanguineous SCAR20 family, the second Portuguese, with two siblings presenting similar clinical features caused by compound heterozygous SNX14 variants: NM_001350532.1:c.1195C>T, p.(Arg399*) combined with a novel complex genomic rearrangement. Quantitative PCR (Q-PCR), long-range PCR and sequencing was used to elucidate the region and mechanisms involved in the latter: two deletions, an inversion and an AG insertion: NM_001350532.1:c.[612+3028_698-2759del;698-2758_698-516inv;698-515_1171+1366delinsAG]. In silico analyses of these variants are in agreement with causality, enabling a genotype-phenotype correlation in both patients. Clinical phenotype includes dystonia and stereotypies never associated with SCAR20. Overall, this study allowed to extend the knowledge of the phenotypic and mutational spectrum of SCAR20, and to validate the role of Sorting nexin-14 in a well-defined neurodevelopmental syndrome, which can lead to cognitive impairment. We also highlight the value of an accurate clinical evaluation and deep phenotyping to disclose the molecular defect underlying highly heterogeneous condition such as intellectual disability.

Usher syndrome and Nebulin-associated myopathy in a single patient due to variants in MYO7A and NEB.

In a patient with Usher syndrome and atypical muscle complaints, we have identified two separate variants in MYO7A andNEB genes by exome sequencing. The homozygous variants in these two recessive genes could explain the full phenotype of our patient.

Clinicopathological correlations of sural nerve biopsies in TTR Val30Met familial amyloid polyneuropathy.

Familial amyloid polyneuropathy with the substitution of methionine for valine at position 30 in the TTR gene is the most common type of hereditary transthyretin amyloidosis. Although several authors have previously reported a size-dependent fibre loss, predominantly involving unmyelinated and small-diameter myelinated fibres, the mechanisms of nerve fibre loss have not been fully understood. In this study, we establish the morphometric pattern of peripheral neuropathy in patients with familial amyloid polyneuropathy and asymptomatic mutation carriers in the biopsies from our archive and correlated the pathological findings with clinical features. A total of 98 patients with familial amyloid polyneuropathy and 37 asymptomatic mutation carriers (TTR Val30Met mutation), aged between 17 and 84 years, who underwent sural nerve biopsy between 1981 and 2017 at Centro Hospitalar Universitário do Porto were studied. Thirty-one controls were included for comparison. The median age at nerve biopsy was 26.0 [interquartile range = 23.5-39.5] years for asymptomatic mutation carriers, 45.0 [35.0-60.0] years for patients with familial amyloid polyneuropathy and 44.0 [30.0-63.0] years for controls. The median duration between nerve biopsy and symptoms' onset was 7.0 [3.3-11.8] years (range: 1-27 years) in the asymptomatic carriers. Most patients were in an earlier disease stage (93% with a polyneuropathy disability scale ≤2). Patients had loss of small and myelinated fibres compared with both asymptomatic carriers and controls (P < 0.001), whereas asymptomatic carriers showed loss of small myelinated fibres when compared with controls (P < 0.05). The loss of myelinated fibres increased with disease progression (P < 0.001), and patients in more advanced clinical stage showed more frequent amyloid deposition in the nerve (P = 0.001). There was a positive correlation between large myelinated fibre density and time to symptoms' onset in the asymptomatic carriers that developed early-onset form of the disease (r = 0.52, P < 0.01). In addition, asymptomatic carriers with amyloid deposition already present in sural nerve biopsies developed symptoms earlier than those with no amyloid (P < 0.01). In conclusion, this study confirms that the loss of small fibre size is an initial event in familial amyloid polyneuropathy, already present in asymptomatic gene carriers, starting several years before the onset of symptoms. We show for the first time that large myelinated fibres' loss and amyloid deposition are pathological features that correlate independently with short period to the onset of symptoms for asymptomatic carriers that developed early-onset form of the disease. These findings are therapeutically relevant, as it would allow for a better interpretation of the role of disease-modifying agents in transthyretin familial amyloid polyneuropathy.

Exonization of an Intronic LINE-1 Element Causing Becker Muscular Dystrophy as a Novel Mutational Mechanism in Dystrophin Gene.

A broad mutational spectrum in the dystrophin (DMD) gene, from large deletions/duplications to point mutations, causes Duchenne/Becker muscular dystrophy (D/BMD). Comprehensive genotyping is particularly relevant considering the mutation-centered therapies for dystrophinopathies. We report the genetic characterization of a patient with disease onset at age 13 years, elevated creatine kinase levels and reduced dystrophin labeling, where multiplex-ligation probe amplification (MLPA) and genomic sequencing failed to detect pathogenic variants. Bioinformatic, transcriptomic (real time PCR, RT-PCR), and genomic approaches (Southern blot, long-range PCR, and single molecule real-time sequencing) were used to characterize the mutation. An aberrant transcript was identified, containing a 103-nucleotide insertion between exons 51 and 52, with no similarity with the DMD gene. This corresponded to the partial exonization of a long interspersed nuclear element (LINE-1), disrupting the open reading frame. Further characterization identified a complete LINE-1 (~6 kb with typical hallmarks) deeply inserted in intron 51. Haplotyping and segregation analysis demonstrated that the mutation had a de novo origin. Besides underscoring the importance of mRNA studies in genetically unsolved cases, this is the first report of a disease-causing fully intronic LINE-1 element in DMD, adding to the diversity of mutational events that give rise to D/BMD.