TMEM151A Variants Cause Paroxysmal Kinesigenic Dyskinesia: A Large-Sample Study.

BACKGROUND: Paroxysmal kinesigenic dyskinesia (PKD) is the most common type of paroxysmal dyskinesias. Only one-third of PKD patients are attributed to proline-rich transmembrane protein 2 (PRRT2) mutations. OBJECTIVE: We aimed to explore the potential causative gene for PKD. METHODS: A cohort of 196 PRRT2-negative PKD probands were enrolled for whole-exome sequencing (WES). Gene Ranking, Identification and Prediction Tool, a method of case-control analysis, was applied to identify the candidate genes. Another 325 PRRT2-negative PKD probands were subsequently screened with Sanger sequencing. RESULTS: Transmembrane Protein 151 (TMEM151A) variants were mainly clustered in PKD patients compared with the control groups. 24 heterozygous variants were detected in 25 of 521 probands (frequency = 4.80%), including 18 missense and 6 nonsense mutations. In 29 patients with TMEM151A variants, the ratio of male to female was 2.63:1 and the mean age of onset was 12.93 ± 3.15 years. Compared with PRRT2 mutation carriers, TMEM151A-related PKD were more common in sporadic PKD patients with pure phenotype. There was no significant difference in types of attack and treatment outcome between TMEM151A-positive and PRRT2-positive groups. CONCLUSIONS: We consolidated mutations in TMEM151A causing PKD with the aid of case-control analysis of a large-scale WES data, which broadens the genotypic spectrum of PKD. TMEM151A-related PKD were more common in sporadic cases and tended to present as pure phenotype with a late onset. Extensive functional studies are needed to enhance our understanding of the pathogenesis of TMEM151A-related PKD. © 2021 International Parkinson and Movement Disorder Society.

The Phenotypic and Genetic Spectrum of Paroxysmal Kinesigenic Dyskinesia in China.

BACKGROUND: Paroxysmal kinesigenic dyskinesia is a spectrum of involuntary dyskinetic disorders with high clinical and genetic heterogeneity. Mutations in proline-rich transmembrane protein 2 have been identified as the major pathogenic factor. OBJECTIVES: We analyzed 600 paroxysmal kinesigenic dyskinesia patients nationwide who were identified by the China Paroxysmal Dyskinesia Collaborative Group to summarize the clinical phenotypes and genetic features of paroxysmal kinesigenic dyskinesia in China and to provide new thoughts on diagnosis and therapy. METHODS: The China Paroxysmal Dyskinesia Collaborative Group was composed of departments of neurology from 22 hospitals. Clinical manifestations and proline-rich transmembrane protein 2 screening results were recorded using unified paroxysmal kinesigenic dyskinesia registration forms. Genotype-phenotype correlation analyses were conducted in patients with and without proline-rich transmembrane protein 2 mutations. High-knee exercises were applied in partial patients as a new diagnostic test to induce attacks. RESULTS: Kinesigenic triggers, male predilection, dystonic attacks, aura, complicated forms of paroxysmal kinesigenic dyskinesia, clustering in patients with family history, and dramatic responses to antiepileptic treatment were the prominent features in this multicenter study. Clinical analysis showed that proline-rich transmembrane protein 2 mutation carriers were prone to present at a younger age and have longer attack duration, bilateral limb involvement, choreic attacks, a complicated form of paroxysmal kinesigenic dyskinesia, family history, and more forms of dyskinesia. The new high-knee-exercise test efficiently induced attacks and could assist in diagnosis. CONCLUSIONS: We propose recommendations regarding diagnostic criteria for paroxysmal kinesigenic dyskinesia based on this large clinical study of paroxysmal kinesigenic dyskinesia. The findings offered some new insights into the diagnosis and treatment of paroxysmal kinesigenic dyskinesia and might help in building standardized paroxysmal kinesigenic dyskinesia clinical evaluations and therapies. © 2020 International Parkinson and Movement Disorder Society.

Case report: Muscular tuberculosis with lower-extremity muscular masses as the initial presentation: Clinicopathological analysis of two cases and review of the literature.

Background: Tuberculosis (TB) is a threat to public health that mostly affects people in developing countries. TB presenting as a soft tissue mass is rare and is usually seen in patients with muscular tuberculosis (MT). Case presentation: In this study, we present the clinical, radiographic, and pathological features of two cases and retrospective evaluations of an additional 28 patients who were diagnosed with MT. More patients were men (60.9%) than women (39.1%), with a male-to-female ratio of 1.6:1. The average age among male and female patients was 38.9 and 30.1 years, respectively. MT usually presents with painful or painless muscular nodules on the lower limbs. Imaging findings, including ultrasound, CT, and MRI, can be used to identify lesions and sites for biopsy. The most typical histopathological feature of MT is granulomatous inflammation with caseous necrosis and epithelioid granulomata. Acid-fast bacilli stain and polymerase chain reaction (PCR) assays are helpful in identifying tubercle bacillus. Conclusion: We describe two MT cases with lower-extremity muscular masses as the initial presentation. The results suggest that muscle biopsy and pathological analysis remain necessary for diagnosis. Most of the patients could be cured with standard antituberculosis therapy.

Case Report: Neuronal Intranuclear Inclusion Disease With Oromandibular Dystonia Onset.

Background: Neuronal intranuclear inclusion disease (NIID) is a rare neurodegenerative disease. Because of variable clinical manifestations, NIID was often misdiagnosed. According to published case reports, the common clinical manifestations of NIID include dementia, muscle weakness, autonomic impairment, sensory disturbance, rigidity, ataxia convulsions, etc. However, no cases of oromandibular dystonia were mentioned. Case Presentation: We describe a case of a 58-year-old woman presenting with mouth involuntary chewing initially. She started to show hand tremors, ataxia, and walking instability until 2 years later. Diffusion-weighted imaging showed high intensity signal along the corticomedullary junction. Fluid-attenuated inversion recovery imaging showed white matter hyperintensity. Electromyography (EMG) indicated peripheral nerve degeneration. Neuropsychological testing showed memory loss. Finally, skin biopsy and GGC repeat expansions in the NOTCH2NLC (Notch 2 N-terminal like C) gene confirmed the diagnosis of NIID. Conclusion: This case demonstrated that oromandibular dystonia could be the first symptom of NIID. This case report provides new characteristics of NIID and broadens its clinical spectrum.

Altered Local Brain Amplitude of Fluctuations in Patients With Myotonic Dystrophy Type 1.

This study is aimed at investigating the characteristics of the spontaneous brain activity in patients with myotonic dystrophy type 1 (DM1). A total of 18 patients with DM1 and 18 healthy controls (HCs) were examined by resting-state functional MRI. Combined methods include amplitude of low-frequency fluctuations (ALFFs), the fractional amplitude of low-frequency fluctuations (fALFFs), and Wavelet transform-based ALFFs (Wavelet-ALFFs) with standardization, percent amplitude of fluctuation (PerAF) with/without standardization were applied to evaluate the spontaneous brain activity of patients with DM1. Compared with HCs, patients with DM1 showed decreased ALFFs and Wavelet-ALFFs in the bilateral precuneus (PCUN), angular gyrus (ANG), inferior parietal, but supramarginal and angular gyri (IPL), posterior cingulate gyrus (PCG), superior frontal gyrus, medial (SFGmed), middle occipital gyrus (MOG), which were mainly distributed in the brain regions of default mode network (DMN). Decreased ALFFs and Wavelet-ALFFs were also seen in bilateral middle frontal gyrus (MFG), inferior frontal gyrus, opercular part (IFGoperc), which were the main components of the executive control network (ECN). Patients with DM1 also showed decreased fALFFs in SFGmed.R, the right anterior cingulate and paracingulate gyri (ACGR), bilateral MFG. Reduced PerAF in bilateral PCUN, ANG, PCG, MOG, and IPLL as well as decreased PerAF without standardization in PCUNR and bilateral PCG also existed in patients with DM1. In conclusion, patients with DM1 had decreased activity in DMN and ECN with increased fluctuations in the temporal cortex and cerebellum. Decreased brain activity in DMN was the most repeatable and reliable with PCUN and PCG being the most specific imaging biomarker of brain dysfunction in patients with DM1.

GGC repeat expansions in NOTCH2NLC causing a phenotype of distal motor neuropathy and myopathy.

BACKGROUND: The expansion of GGC repeat in the 5' untranslated region of the NOTCH2NLC has been associated with various neurogenerative disorders of the central nervous system and, more recently, oculopharyngodistal myopathy. This study aimed to report patients with distal weakness with both neuropathic and myopathic features on electrophysiology and pathology who present GGC repeat expansions in the NOTCH2NLC. METHODS: Whole-exome sequencing (WES) and long-read sequencing were implemented to identify the candidate genes. In addition, the available clinical data and the pathological changes associated with peripheral nerve and muscle biopsies were reviewed and studied. RESULTS: We identified and validated GGC repeat expansions of NOTCH2NLC in three unrelated patients who presented with progressive weakness predominantly affecting distal lower limb muscles, following negative results in an initial WES. We found intranuclear inclusions with multiple proteins deposits in the nuclei of both myofibers and Schwann cells. The clinical features of these patients are compatible with the diagnosis of distal motor neuropathy and rimmed vacuolar myopathy. INTERPRETATION: These phenotypes enrich the class of features associated with NOTCH2NLC-related repeat expansion disorders (NRED), and provide further evidence that the neurological symptoms of NRED include not only brain, spinal cord, and peripheral nerves damage, but also myopathy, and that overlapping symptoms might exist.

Altered structural and functional connectivity in CSF1R-related leukoencephalopathy.

CSF1R-related leukoencephalopathy is a rare white-matter encephalopathy characterized by motor and neuropsychiatric symptoms due to colony-stimulating factor 1 receptor (CSF1R) gene mutation. Few studies have investigated the intrinsic brain alternations of patients with CSF1R-related leukoencephalopathy. We aim to evaluate the structural and functional changes in those patients. Seven patients with CSF1R-related leukoencephalopathy and 15 age-matched healthy controls (HCs) underwent multimodal magnetic resonance imaging (MRI), including high-resolution T1-weighted imaging, T2-weighted fluid attenuated inversion recovery imaging, diffusion-weighted imaging, diffusion kurtosis imaging (DKI) and resting-state functional MRI. First, to detect structural alterations, the gray matter volumes were compared using voxel-based morphometry analyses. Second, DKI parametric maps were used to evaluate the white matter (WM) connectivity changes. Finally, we constructed a seed-based resting-state functional connectivity matrix based on 90 regions of interest and examined the functional network changes of CSF1R-related leukoencephalopathy. Unlike the HCs, patients with CSF1R-related leukoencephalopathy predominantly had morphological atrophy in the bilateral thalamus and left hippocampus. In addition, the abnormal diffusivity was mainly distributed in the splenium of the corpus callosum, periventricular regions, centrum semiovale, subcortical U-fibers and midline cortex structures. Moreover, the patients had significantly reduced functional connectivity between the bilateral caudate nucleus and their contralateral hippocampus. Therefore, in addition to hyperintensity on the T2-weighted images, CSF1R-related leukoencephalopathy also showed abnormal structural and functional alterations, including subcortical atrophy and reduced functional connectivity, as well as altered diffuse parameters in the WM and subcortical regions. These findings expand our understanding of the potential pathophysiologic mechanism behind this hereditary disease.

New phenotype of DCTN1-related spectrum: early-onset dHMN plus congenital foot deformity.

OBJECTIVE: To describe the clinical and genetic features of two patients with different phenotypes due to various Dynactin 1 (DCTN1) gene mutations and further explore the phenotype-genotype relationship. METHODS: Patient 1 is a 23-year-old man with congenital foot deformity and life-long distal muscle weakness and atrophy. Patient 2 is a 48-year-old woman with adult-onset progressive weakness, lower limbs atrophy, and pyramid bundle signs. Electrophysiology test showed normal nerve conduction velocity of both patients and neurogenic changes in needle electromyography. Open sural nerve biopsy for Patient 1 showed slight loss of myelinated nerve fibers. Both patients were performed with whole-exome sequencing followed by functional study of identified variants. RESULTS: Two mutations in DCTN1 gene were identified in Patient 1 (c.626dupC) and Patient 2 (c.3823C>T), respectively. In vitro, the wild type mostly located in cytoplasm and colocalized with α-tubulin. However, c.626dupC tended to be trapped into nuclear and the c.3823C>T formed cytoplasmic aggregates, both losing colocalization with α-tubulin. Western blotting showed a truncated mutant with less molecular weight of c.626dupC was expressed. INTERPRETATION: We identify two novel DCTN1 mutations causing different phenotypes: (1) early-onset distal hereditary motor neuropathy plus congenital foot malformation and (2) amyotrophic lateral sclerosis, respectively. We provide the initial evidence that foot developmental deficiency probably arises from subcellular localizing abnormality of Dynactin 1, revealing DCTN1-related spectrum is still expanding.

[Two novel mutations of GJB1 gene associated with typical X-linked Charcot-Marie-Tooth disease].

OBJECTIVE: To analyze the relationship between phenotype and genotype and the role of immune cells in the pathogenesis of X-linked Charcot-Marie-Tooth disease (CMT1X). METHODS: The probands of the two families with X-linked dominant inherited peripheral neuropathy were evaluated clinically, electrophysiologically, pathologically and genetically. The available family members were genetic analyzed and the novel mutations were compared with other known ones. RESULTS: (1) In both families, affected members presented progressive weakness and wasting of distal extremities and it seems that males suffered more severely than affected females with onset in the first decade of their life. Proband of family 1 showed moderately elevated CSF protein and marked increase of IgG-syn in CSF.(2) Nerve conduction velocity (NCV) of the peripheral nerves was intermediately slow in both motor and sensory nerves exhibiting the features of demyelination. Brain-stem auditory evoked potentials (BAEPs) was abnormal in the proband of family 1: delayed I-III interpeak intervals were recorded but with normal III-V interpeak intervals. (3) Sural nerve biopsy in the probands of the two families showed a prominent distinguished loss of myelinated fibers and a few clusters of regenerating axons without conspicuous onion-bulb formations. Thinly myelinated fibers was prominent in family 2 but not in family 1. Immunohistochemical staining showed that there were positive CD68 cells in the endoneurial space and lamellar sheath. (4) By genetic testing, we identified two novel missense mutations of GJB1 gene, which resulted in Ile127Phe amino acid substitution in family 1(located in the intracellular loop of connexin 32) and Asp178Gly amino acid substitution in family 2 (located in the 2(nd) extracellular loop of CX32), respectively. Both mutations were highly conserved in low species and were predicted to be possibly damaging through Polyphen prediction tool. CONCLUSION: The two novel GJB1 gene mutations cause a spectrum of clinical manifestations of CMT1X in both families. However, the mutations site of CX32 alone cannot predict these phenotypic variations in CMT1X fully. The immune system may be involved in the pathogenesis of the disease.

Congenital disorder of glycosylation type 1T with a novel truncated homozygous mutation in PGM1 gene and literature review.

The congenital disorders of glycosylation are a group of clinically and biochemically heterogeneous diseases characterized by multisystem involvement due to glycosylation defect of protein and lipid. Here we report a 49-year-old man with exercise-induced fatigue and pain of muscle, tachypnea, cleft palate and bifid uvula. Exercise induced elevation of serum creatine kinase (CK), ammonia and lactic acid was recorded. The abnormal levels of myoglobin, CK-MB and LDH as well as S-T elevation in electrocardiogram were observed in repeated hospitalization recordings. Electromyography showed myopathic damage. Repetitive nerve stimulation test of low rates showed decrement in the left deltoid muscle. He was identified with a novel homozygous frameshift variant in Phosphoglucomutase type 1 gene (c.405delT p.N135Kfs*9) by whole exome sequencing. Muscle biopsy exhibited minimal variation in fiber size without abnormal glycogen accumulation. Compared with controls', the patient's sample showed no signal at ∼61 kDa using N- or C-terminus antibody of Phosphoglucomutase type 1 in western blotting. A signal at ∼20 kDa was detected in patient using N-terminus antibody. Immunofluorescence revealed trace expression of C-terminus and a much lower expression of N-terminus on the sarcolemma than normal. Our findings indicate that c.405delT encodes a truncated protein with abnormal distribution and expression in skeletal muscle. In conclusion, genes associated with congenital disorders of glycosylation should be analyzed in patients with maxillofacial dysplasia, exertional weakness, cardiac involvement and exercise-induced-ammoniemia, without glycogen storage in skeletal muscle.

Lysosomal degradation of GMPPB is associated with limb-girdle muscular dystrophy type 2T.

OBJECTIVE: GDP-mannose pyrophosphorylase B (GMPPB) related phenotype spectrum ranges widely from congenital myasthenic syndrome (CMS), limb-girdle muscular dystrophy type 2T (LGMD 2T) to severe congenital muscle-eye-brain syndrome. Our study investigates the clinicopathologic features of a patient with novel GMPPB mutations and explores the pathogenetic mechanism. METHODS: The patient was a 22-year-old woman with chronic proximal limb weakness for 9 years without cognitive deterioration. Weakness became worse after fatigue. Elevated serum creatine kinase and decrements on repetitive nerve stimulation test were recorded. MRI showed fatty infiltration in muscles of lower limbs and shoulder girdle on T1 sequence. Open muscle biopsy and genetic analysis were performed. RESULTS: Muscle biopsy showed myogenic changes. Two missense mutations in GMPPB gene (c.803T>C and c.1060G>A) were identified in the patient. Western blotting and immunostaining showed GMPPB and α-dystroglycan deficiency in the patient's muscle. In vitro, mutant GMPPB forming cytoplasmic aggregates completely colocalized with microtubule-associated protein 1 light chain 3-II (LC3-II), a classical marker of autophagosome. Degradation of GMPPB was accompanied by an upregulation of LC3-II, which could be restored by lysosomal inhibitor leupeptin. INTERPRETATION: We identified two novel GMPPB mutations causing overlap phenotype between LGMD 2T and CMS. We provided the initial evidence that mutant GMPPB colocalizes with autophagosome at subcellular level. GMPPB mutants degraded by autophagy-lysosome pathway is associated with LGMD 2T. This study shed the light into the enzyme replacement which could become one of the therapeutic targets in the future study.

Clinicopathologic characterization and abnormal autophagy of CSF1R-related leukoencephalopathy.

BACKGROUND: CSF1R-related leukoencephalopathy, also known as hereditary diffuse leukoencephalopathy with spheroids (HDLS), is a rare white-matter encephalopathy characterized by motor and neuropsychiatric symptoms due to colony-stimulating factor 1 receptor (CSF1R) gene mutation. Few of CSF1R mutations have been functionally testified and the pathogenesis remains unknown. METHODS: In order to investigate clinical and pathological characteristics of patients with CSF1R-related leukoencephalopathy and explore the potential impact of CSF1R mutations, we analyzed clinical manifestations of 15 patients from 10 unrelated families and performed brain biopsy in 2 cases. Next generation sequencing was conducted for 10 probands to confirm the diagnosis. Sanger sequencing, segregation analysis and phenotypic reevaluation were utilized to substantiate findings. Functional examination of identified mutations was further explored. RESULTS: Clinical and neuroimaging characteristics were summarized. The average age at onset was 35.9 ± 6.4 years (range 24-46 years old). Younger age of onset was observed in female than male (34.2 vs. 39.2 years). The most common initial symptoms were speech dysfunction, cognitive decline and parkinsonian symptoms. One patient also had marked peripheral neuropathy. Brain biopsy of two cases showed typical pathological changes, including myelin loss, axonal spheroids, phosphorylated neurofilament and activated macrophages. Electron microscopy disclosed increased mitochondrial vacuolation and disorganized neurofilaments in ballooned axons. A total of 7 pathogenic variants (4 novel, 3 documented) were identified with autophosphorylation deficiency, among which c.2342C > T remained partial function of autophosphorylation. Western blotting disclosed the significantly lower level of c.2026C > T (p.R676*) than wild type. The level of microtubule associated protein 1 light chain 3-II (LC3-II), a classical marker of autophagy, was significantly lower in mutants expressed cells than wild type group by western blotting and immunofluorescence staining. CONCLUSIONS: Our findings support the loss-of-function and haploinsufficiency hypothesis in pathogenesis. Autophagy abnormality may play a role in the disease. Repairing or promoting the phosphorylation level of mutant CSF1R may shed light on therapeutic targets in the future. However, whether peripheral polyneuropathy potentially belongs to CSF1R-related spectrum deserves further study with longer follow-up and more patients enrolled. TRIAL REGISTRATION: ChiCTR, ChiCTR1800015295. Registered 21 March 2018.

Retinal arterial abnormalities correlate with brain white matter lesions in cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy.

PURPOSE: The aim of this study is to determine the relationship between retinal abnormalities and brain white matter hyper-intensities (WMH) in symptomatic patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL). METHODS: Fifteen patients with CADASIL and fifteen age-matched healthy control individuals were enrolled in this study. Ophthalmological examinations were performed on all subjects and all patients with CADASIL underwent cerebral MRI scanning. Retinal artery abnormalities were graded according to the Keith-Wagener-Barker hypertensive retinopathy classification. WMH were classified as punctuate (Grade 1), nodular or early confluent (Grade 2) and diffusly confluent (Grade 3). Partial correlation was used to assess the relationship between retinal abnormalities and WMH, controlling for age. RESULTS: Retinal arteriole narrowing existed in 15 cases and 2 controls, with Grade 2 and Grade 3 being the most common grading of retinal artery narrowing in patients with CADASIL. All patients had WMH on MRI, rated as Grade 1 in one patient, Grade 2 in five patients and Grade 3 in nine patients. The correlation coefficient of retinal arteriole narrowing and WMH was 0.546 (P < 0.05). CONCLUSION: Retinal arteriole narrowing may be associated with the severity of the cerebral lesions in CADASIL.

[Mitochondrial DNA mutation analysis in 97 Chinese patients with mitochondrial cephalomyopathy].

OBJECTIVE: To investigate the characteristics of mitochondrial DNA mutations and genotype-phenotype correlations in mitochondrial encephalomyopathies. METHODS: Biopsy of skeletal muscle and collection of peripheral blood samples were conducted among 97 patients with mitochondrial encephalomyopathies. Southern blotting, PCR-RFLP and direct sequencing of PCR products were performed to search large scale deletions, and common and uncommon pathological point mutations in the muscle and/or blood mtDNA. RESULTS: Seventy-seven patients were identified to be with mitochondrial DNA mutations, including single large deletion (n = 21), multiple large-scale deletions (n = 4), A3243G point mutation (n = 43), A8344G point mutation (n = 6), T8993G mutation (n = 1), T8993C mutation (n = 1), and T3271C mutation (n = 1). Total mtDNA sequencing revealed 4 different novel point mutations in four unrelated patients with isolated mitochondrial myopathy. CONCLUSION: The type and frequency of mtDNA mutations in this series of Chinese mitochondrial encephalopathies are consistent with those reported abroad, Although there is some association between the genotype and phenotype, heterogeneity in phenotype and genotype is also a prominent feature seen in this series of patients, especially those with A3243G mutation.

Progressive myoclonus epilepsy without renal failure in a Chinese family with a novel mutation in SCARB2 gene and literature review.

PURPOSE: To describe the clinical and genetic features of a Chinese progressive myoclonus epilepsy (PME) patient related with SCARB2 mutation without renal impairment and review 27 SCARB2-related PME patients from 11 countries. METHODS: The patient was a 27-year-old man with progressive action myoclonus, ataxia, epilepsy, dysarthria and absence of cognitive deterioration. Renal functional test was normal. Electroencephalography (EEG) showed progressively slowed background activity and sporadic generalized spike-and-wave discharges. Electromyography (EMG) showed slowed motor and sensory nerve conduction velocities and distal motor latency delay accompanied by normal compound motor action potential (CMAP) and amplitudes of sensory nerve action potential (SNAP). The amplitude of cortical components of brainstem auditory-evoked potential (BAEP) was normal with slightly prolonged latencies. Generalized atrophy, ventricle enlargement and white matter degeneration was observed in brain magnetic resonance imaging (MRI). Open muscle biopsy and genetic analysis were performed. Two hundred healthy individuals were set for control. Quantitative real time PCR (qPCR), western blotting and immunofluorescence were carried out to evaluate the fate of the SCARB2 mRNA and lysosomal-membrane type 2 (LIMP2) protein level. RESULTS: One homozygous mutation in SCARB2 gene (c.1187 + 5G > T) was identified in the patient. Each of his parents carried a heterozygous variant. This mutation was not detected among the healthy controls and predicted to be damaging or disease causing by prediction tools. qPCR revealed a significantly lower level of SCARB2 mRNA in peripheral blood cell of the proband compared with his parents and healthy control individuals. Muscle biopsy showed mild variation in fiber size. Western blotting and immunofluorescence detected an extremely weak signal of LIMP2 protein from skeletal muscle of the proband. CONCLUSION: In this study, we identified a SCARB2-related PME patient with normal renal function and a novel homozygous splicing mutation. SCARB2 gene should be analyzed in patients with progressive action myoclonus, epilepsy, peripheral neuropathy, without cognitive deterioration or renal failure.

The study of exercise tests in paroxysmal kinesigenic dyskinesia.

OBJECTIVE: To unravel if there was muscular ion channel dysfunction in paroxysmal kinesigenic dyskinesia (PKD) patients using the exercises tests (ET). METHODS: Sixty PKD patients including 28 PRRT2 mutations carriers were enrolled in this study, as well as 19 hypokalaemic periodic paralysis (HypoPP) patients as the positive controls and 45 healthy subjects as the negative controls. ET including long exercise test (LET) and short exercise test (SET) was performed in the corresponding subjects. RESULTS: In the LET, both the overall PKD patients and HypoPP patients had greater CMAP amplitude and area increments during exercise than healthy controls. At most 25% of PKD patients were identified from the normality with greater amplitude increment than the area. On the contrary, 50% of HypoPP patients were differentiated with greater area increment than the amplitude. More percentage of PRRT2- patients than PRRT2+ patients had abnormal average amplitude increment. Unexpectedly, five PKD patients had abnormal maximum CMAP amplitude decrements after exercise in the LET, and one had abnormal maximum immediate amplitude decrement in the SET. CONCLUSIONS: Distinct ET manifestations were found in PKD patients compared to normal controls and HypoPP patients. SIGNIFICANCE: Abnormal muscle membrane excitability might be involved in the mechanisms responsible for PKD.

Novel ATM mutations with ataxia-telangiectasia.

Ataxia telangiectasia is an autosomal recessive multisystem disorder characterized by progressive cerebellar ataxia with onset in childhood, oculocutaneous telangiectasia, increased serum alpha-fetoprotein, immunodeficiency, chromosomal instability, and radiation hypersensitivity. Ataxia-telangiectasia mutated gene (ATM) is one of the known genes to be associated with ataxia telangiectasia. We reported the clinical and genetic findings of three early-onset Chinese patients who demonstrated ataxia, oculomotor apraxia, choreoathetosis, myoclonus and telangiectasia of eyes. Sequence analysis of ATM revealed two known nonsense mutations c.8287C>T and c.9139C>T in the siblings. Though the siblings carried the same mutations, they showed different clinical features involving strephenopodia, exotropia, torsion dystonia, myoclonus and extrapyramidal impairments. The other patient was compound heterozygotes for ATM: c.8911C>T and c.7141_7151delAATGGAAAAAT, both of which were not reported previously and not found in 200 control chromosomes. This study widens the spectrum of mutations and phenotypes in ataxia telangiectasia.

Mutations of SCN4A gene cause different diseases: 2 case reports and literature review.

SCN4A encodes the Nav1.4 channel and mutations in SCN4A lead to different ionic channelopathies. In this study, one sporadic individual of periodic paralysis, one paramyotonia family and 200 normal healthy controls are enrolled. Genomic DNA was extracted from peripheral blood leukocytes, followed by polymerase chain reaction and DNA sequencing of candidate genes, including SCN4A and CACNA1S. As a result, heterozygous mutations c.2024G>A (R675Q) and c.1333G>A (V445M) of gene SCN4A were identified in the hypokalemic periodic paralysis patient and the paramyotonia congenita family respectively. Both mutations were not detected in healthy controls. Compared with reported cases, patients with mutation R675Q usually do not present hypokalemic periodic paralysis but hyperkalemic or normokalemic periodic paralysis. The mutation V445M was first reported in Chinese patients with nondystrophic myotonias. In addition, we carried out literature review by summarizing clinical features of the 2 mutations and establish the genotype-phenotype correlations to provide guidance for diagnosis.

Myotonia congenita: novel mutations in CLCN1 gene.

Myotonia congenita belongs to the group of non-dystrophic myotonia caused by mutations of CLCN1gene, which encodes human skeletal muscle chloride channel 1. It can be inherited either in autosomal dominant (Thomsen disease) or recessive (Becker disease) forms. Here we have sequenced all 23 exons and exon-intron boundaries of the CLCN1 gene, in a panel of 5 unrelated Chinese patients with myotonia congenita (2 with dominant and 3 with recessive form). In addition, detailed clinical analysis was performed in these patients to summarize their clinical characteristics in relation to their genotypes. Mutational analyses revealed 7 different point mutations. Of these, we have found 3 novel mutations including 2 missense (R47W, V229M), one splicing (IVS19+2T>C), and 4 known mutations (Y261C,G523D, M560T, G859D). Our data expand the spectrum of CLCN1 mutations and provide insights for genotype-phenotype correlations of myotonia congenita in the Chinese population.