[A case of anti-SRP antibody-positive immune-mediated necrotizing myopathy triggered by human parvovirus B19 infection].

We have reported a case of a 44-year-old woman with anti-signal recognition particle (SRP) antibody-positive immune-mediated necrotizing myopathy triggered by human parvovirus B19 (PVB19) infection. She was admitted to the hospital because of lower leg edema and muscle weakness after erythema infectiosum. Magnetic resonance imaging of the lower extremities revealed high signals in the proximal muscles and subcutaneous edema on STIR. Muscle biopsy showed myofiber regenerative changes and variation in fiber size. A myositis-specific autoantibody profile indicated a positive result for anti-SRP antibodies. We diagnosed the patient with immune-mediated necrotizing myopathy (IMNM). Muscle strength and subcutaneous edema improved gradually in 3 months following immunotherapy. This is the first case report of an IMNM associated with PVB19 infection.

Complex hereditary peripheral neuropathies caused by novel variants in mitochondrial-related nuclear genes.

Mitochondrial disorders are a group of clinically and genetically heterogeneous multisystem disorders and peripheral neuropathy is frequently described in the context of mutations in mitochondrial-related nuclear genes. This study aimed to identify the causative mutations in mitochondrial-related nuclear genes in suspected hereditary peripheral neuropathy patients. We enrolled a large Japanese cohort of clinically suspected hereditary peripheral neuropathy patients who were mutation negative in the prescreening of the known Charcot-Marie-Tooth disease-causing genes. We performed whole-exome sequencing on 247 patients with autosomal recessive or sporadic inheritance for further analysis of 167 mitochondrial-related nuclear genes. We detected novel bi-allelic likely pathogenic/pathogenic variants in four patients, from four mitochondrial-related nuclear genes: pyruvate dehydrogenase beta-polypeptide (PDHB), mitochondrial poly(A) polymerase (MTPAP), hydroxyacyl-CoA dehydrogenase/3-ketoacyl-CoA thiolase/enoyl-CoA hydratase, beta subunit (HADHB), and succinate-CoA ligase ADP-forming beta subunit (SUCLA2). All these patients showed sensory and motor axonal polyneuropathy, combined with central nervous system or multisystem involvements. The pathological analysis of skeletal muscles revealed mild neurogenic changes without significant mitochondrial abnormalities. Targeted screening of mitochondria-related nuclear genes should be considered for patients with complex hereditary axonal polyneuropathy, accompanied by central nervous system dysfunctions, or with unexplainable multisystem disorders.

Treatment of transthyretin familial amyloid polyneuropathy with tafamidis: a case report.

INTRODUCTION: Familial amyloid polyneuropathy (FAP) is a rare hereditary disorder caused by mutations in the transthyretin (TTR) gene. Tafamidis is a TTR stabilizer able to prevent TTR tetramer dissociation, and several studies have demonstrated its safety and efficacy at slowing the progression of neuropathy in FAP caused by the TTR Val30Met mutation. However, nerve conduction study (NCS) and electromyography (EMG) results have yet to be reported in relation to FAP progression during tafamidis therapy. CASE PRESENTATION: A 71-year-old man was admitted to the hospital because of severe numbness and walking difficulties. He did not complain of any autonomic dysfunction or visual disturbance, and he had no family history of neuromuscular disorders. A NCS and EMG indicated length-dependent axonal sensorimotor polyneuropathy. A sural nerve biopsy revealed amyloid deposits, and genetic testing demonstrated a TTR Val30Met mutation. We diagnosed the patient with FAP and treated him using tafamidis therapy. One year later, the patient is still on tafamidis therapy, and his symptoms have shown no significant change. The NCS showed no changes in the compound muscle action potential amplitudes of the left ulnar nerve, while EMG showed the fibrillation/positive sharp wave to have disappeared from the patient's upper limb. We conclude from these findings a slowing of the neurologic progression. CONCLUSIONS: Tafamidis was effective in slowing the neurologic progression over one year in a FAP patient with the TTR Val30Met mutation, and NCS and EMG were useful for assessing this therapeutic effect.

Mitochondrial trifunctional protein deficiency: an adult patient with similar progress to Charcot-Marie-Tooth disease.

A 45-year-old man presented to us due to slowly progressive muscle weakness and sensory disturbances in his lower limbs since his 40's. He reported multiple episodes of exercise-induced severe muscle fatigue and brown urine in his childhood, which disappeared by age 20. A nerve conduction study showed peripheral axonal neuropathy and then Charcot-Marie-Tooth disease (CMT) was considered as the most likely diagnosis; however, exome sequencing failed to identify a mutation in the known genes of CMTs. Since age 55, he recurrently developed severe rhabdomyolysis that required hospitalization. On suspicion of lipid metabolism disorders, we performed serum acylcarnitine analysis, and which revealed mildly elevated long-chain fatty acids. We re-examined variants obtained via exome sequencing and found a mutation in HADHB. Mitochondrial trifunctional protein (MTP) deficiency is a rare autosomal recessive disorder of mitochondrial fatty acid beta-oxidation caused by HADHA or HADHB mutation. It can be a life-threatening multiorgan disorder with early infantile onset, but it can also present in childhood or adolescence with peripheral neuropathy and recurrent rhabdomyolysis. This case of adult-diagnosed MTP deficiency was characterized by slowly progressive peripheral neuropathy masquerading CMT in addition to muscular symptoms. MTP deficiency should be considered in patients with the combination of peripheral neuropathy and recurrent rhabdomyolysis.

Imaging-based differential diagnosis between multiple system atrophy and Parkinson's disease.

There are many tools for differentiating between multiple system atrophy with predominant parkinsonian features (MSA-P) and Parkinson's disease (PD). These include middle cerebellar peduncle (MCP) width, apparent diffusion coefficient (ADC) value of the putamen and cerebellum, and (123)I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy images. We aimed to directly compare the above-mentioned methods, and to determine the optimal tool for differential diagnosis. Eleven patients with MSA-P and 36 patients with PD were enrolled. Of these, 7 patients with MSA-P and 14 patients with PD were chosen as background-matched subjects. We measured MCP width, ADC value of the putamen and cerebellum, and MIBG myocardial scintigraphy images. Area under curve (AUC) of receiver operating characteristic (ROC) was assessed to compare the above-mentioned methods. MCP width and ADC value of the putamen may be helpful for differentiating between MSA-P and PD relative to other methods in background-matched patients (MCP, AUC=0.95; putamen ADC, AUC=0.88; cerebellar ADC, AUC=0.70; MIBG, AUC=0.78). Similar AUCs were seen in all patients with different backgrounds. Our findings suggested that MCP width and ADC value of the putamen could be superior to ADC value of the cerebellum and MIBG uptake for differentiating between MSA-P and PD.

Late-onset myasthenia gravis is predisposed to become generalized in the elderly.

OBJECTIVE: The continuous increase in the number of patients presenting with late-onset myasthenia gravis (LOMG) underscores the need for a better understanding of the clinical course and the establishment of an optimal therapeutic strategy. We aimed to clarify factors associated with clinical outcomes in LOMG. METHODS: We retrospectively reviewed the clinical profiles of 40 patients with early-onset MG (EOMG) (onset age: 49 years or younger), 30 patients with non-elderly LOMG (onset age: 50-64 years), and 28 patients with elderly LOMG (onset age: 65 years or older) and compared the subgroups according to onset age and thymus status. The evaluated parameters were MGFA classification before treatment, MG-ADL score, complicating diseases, antibody titer, treatment, and MGFA post-intervention status. RESULTS: Elderly LOMG patients showed transition to generalized symptoms at a higher frequency and underwent thymectomy less frequently than EOMG and non-elderly LOMG patients (p < 0.001). The frequencies of crisis and plasmapheresis were significantly lower in thymectomized LOMG patients without thymoma than in thymectomized LOMG patients with thymoma or non-thymectomized LOMG patients (p < 0.01, P < 0.05, respectively). However, the outcome was not significantly different. All of the thymectomized LOMG patients without thymoma presenting with hyperplasia or thymic cyst had a favorable clinical course. CONCLUSIONS: Our study showed that elderly LOMG patients are more prone to severity, suggesting that they require aggressive immunomodulatory therapy.

Late-onset spastic paraplegia: Aberrant SPG11 transcripts generated by a novel splice site donor mutation.

We identified a novel homozygous mutation in the splice site donor (SSD) of intron 30 (c.5866+1G>A) in consanguineous Japanese SPG11 siblings showing late-onset spastic paraplegia using the whole-exome sequencing. Phenotypic variability was observed, including age-at-onset, dysarthria and pes cavus. Coding DNA sequencing revealed that the mutation affected the recognition of the constitutive SSD of intron 30, splicing upstream onto a nearby cryptic SSD in exon 30. The use of constitutive splice sites of intron 29 was confirmed by sequencing. The mutant transcripts are mostly subject to degradation by the nonsense-mediated mRNA decay system. SPG11 transcripts, escaping from the nonsense-mediated mRNA decay pathway, would generate a truncated protein (p.Tyr1900Phefs5X) containing the first 1899 amino acids and followed by 4 aberrant amino acids. This study showed a successful clinical application of whole-exome sequencing in spastic paraplegia and demonstrated a further evidence of allelic heterogeneity in SPG11. The confirmation of aberrant transcript by splice site mutation is a prerequisite for a more precise molecular diagnosis.

The effect of tremor onset on middle cerebellar peduncle of Parkinson's disease.

The majority of studies of Parkinson's disease (PD) focused on basal ganglia initially; however, accumulating evidence suggests cerebellar involvement in pathophysiology. We aimed to investigate the effects of tremor onset on middle cerebellar peduncle (MCP) width of PD patients and of disease duration on differential diagnosis. We measured MCP width of 81 PD, 34 multiple system atrophy (MSA) and 16 normal controls, using MRI. A meta-analysis was performed including two previous and the present studies. We carried out correlation analysis between disease duration and MCP width separately in subgroup of PD with or without tremor onset. Receiver operating characteristic curves were analyzed. Our meta-analysis indicated that MCP width was significantly smaller in MSA relative to PD with homogeneous studies. There was significant correlation between disease duration and MCP width in PD without tremor onset. In contrast, there was no correlation observed in PD with tremor onset. Subclassification according to disease duration showed improved area under curve of PD vs. MSA with predominant parkinsonian features. MCP width could be a valuable tool for differential diagnosis. Our finding suggested that MCP was impaired in advanced stage of PD without tremor onset as part of the abnormality of the cerebellar system.

Abnormal gating of axonal slow potassium current in cramp-fasciculation syndrome.

OBJECTIVE: Cramp-fasciculation syndrome (CFS) is a heterogeneous condition with multiple underlying causes. Although dysfunction of slow K(+) channels has been reported in patients with CFS, testing all potential candidates for this problem using conventional in vitro functional analysis would be prohibitively cost- and labor-intensive. However, relatively economical and non-invasive nerve-excitability testing can identify ion channel dysfunction in vivo when combined with numerical modeling. METHODS: Patients with CFS underwent nerve conduction study, needle electromyography, and nerve excitability testing. Mathematical modeling of axonal properties was applied to identify the pathophysiology. RESULTS: Four patients had distinct electrophysiological findings (i.e., fasciculation potentials, doublet/multiplet motor unit potentials, and sustained F responses); excitability testing showed the following abnormalities: reduction of accommodation during prolonged depolarization, lack of late sub excitability after a supramaximal stimulation, and reduction of the strength-duration time constant. Mathematical modeling showed a loss of voltage-dependence of a slow K(+) current. None of these patients had a mutation in the KCNQ2, 3, or 5 genes. CONCLUSIONS: This study showed that patients with CFS might have abnormal kinetics in a slow K(+) current. SIGNIFICANCE: Nerve-excitability testing may aid the decision to start therapeutic intervention such as administration of slow K(+) channel openers.

Which target is best for patients with Parkinson's disease? A meta-analysis of pallidal and subthalamic stimulation.

BACKGROUND: There is a growing body of evidence demonstrating that deep brain stimulation (DBS) of globus pallidus internus (GPi DBS) and subthalamic nucleus (STN DBS) are effective treatment for patients with Parkinson's disease (PD). However, it remains controversial whether the best stimulation target for a PD patient is GPi or STN. METHODS: A computer literature search of PubMed was carried out. We included randomised studies with direct comparison between targets. The outcome of unified PD rating scale (UPDRS) III was expressed as the standardised mean difference (SMD) between targets in baseline to endpoint change. Pooled risk ratio (RR) between targets was also used to assess adverse events. RESULTS: Four studies, comprising a total sample size of 502 PD patients (254 GPi DBS, 248 STN DBS), were included in this meta-analysis. The overall effect of GPi DBS on UPDRS III was not significantly different from STN DBS (SMD=0.19, 95% CI -0.2 to 0.58, p=0.34, four studies, n=448). This result was heterogeneous (p=0.03, I(2)=66%). In terms of adverse events, depression was significantly less frequent in patients with GPi DBS than STN DBS with homogeneous studies (pooled RR=0.53, 95% CI 0.31 to 0.90, p=0.02, three studies, n=479, I(2)=48%). CONCLUSIONS: The effect of GPi DBS was similar to STN DBS except for depression, however, only three studies described depression as adverse events. We need additional randomised trials with direct comparison between targets based on unified scoring of adverse events.

Exome sequencing reveals a novel MRE11 mutation in a patient with progressive myoclonic ataxia.

Progressive myoclonic ataxia (PMA) is a clinical syndrome defined as progressive ataxia and myoclonus and infrequent seizures in the absence of progressive dementia. Due to the extremely heterogeneous nature of PMA, a large proportion of PMA cases remain molecularly undiagnosed. The aim of this study was to clarify the molecular etiology of PMA. The patient was a 52-year-old female from consanguineous parents. She developed a jerking neck movement at age 9, which gradually expanded to her entire body. On physical examination at age 47, she exhibited generalized, spontaneous myoclonus that occurred continuously. She also presented with mild limb and truncal ataxia. An electroencephalogram revealed no abnormalities. A brain MRI displayed no atrophy of the cerebellum. Electrophysiological studies suggested myoclonus of a subcortical origin. For further evaluation, we performed exome sequencing, and we identified a novel homozygous missense mutation in the MRE11 gene (NM_005590:c.140C>T:p.A47V). Subsequently, we analyzed the expression of MRE11 and related proteins (RAD50 and NBS1) via Western blot, and they were markedly decreased compared to a healthy control. Mutations in the MRE11 gene have been known to cause an ataxia-telangiectasia-like (ATLD) disorder. Accumulating evidence has indicated that its wide phenotypic variations in ATLD correspond to genotypic differences. Interestingly, our case exhibited a relatively mild decrease in NBS1 compared to previously reported cases of a homozygous missense mutation, which may account for the milder phenotype in this patient. Moreover, together with a recently reported case of an MRE11 mutation, it is suggested that MRE11 mutations can present as PMA.

[Dystonia genes and elucidation of their roles in dystonia pathogenesis].

Identification of causative genes for hereditary dystonia and elucidation of their functions are crucial for better understanding of dystonia pathogenesis. As seen in other hereditary neurologic disorders, intra- and inter-familial clinical variations have been demonstrated in hereditary dystonia. Asymptomatic carriers can be found due to alterations in penetrance, generally reduced in succeeding generations. Current known dystonia genes include those related to dopamine metabolism, transcription factor, cytoskeleton, transport of glucose and sodium ion, etc. It has been reported that effects of deep brain stimulation can vary significantly depending on genotype. Accumulation of genotype-outcome correlations would contribute to treatment decisions for dystonia patients.

[New medications for dystonia].

Although there are some newly-developed options to treat dystonia, its medical treatment is not always satisfactory. Zolpidem, an imidazopyridine agonist with a high affinity to benzodiazepine receptor subtype ω1, has been reported to improve clinical symptoms of dystonia in some cases. We conducted an open-label study to assess the efficacy of zolpidem in 34 patients with primary dystonia patients, The Burke Fahn Marsden Dystonia Rating Scale (BFMDRS) scores in the patients were decreased from 7.2 ± 7.9 to 5.5 ± 5.0 after zolpidem therapy (P=0.042). Next we evaluated 55 patients with primary and secondary dystonia, 16 of 55 patients (29%) responded to zolpidem, and secondary dystonia, particularly post-traumatic dystonia, was more responsive than primary dystonia (5 of 11 [46%] vs 11 of 44 [25%]). The efficacy of zolpidem was comparable to that of other oral medications in our previous study; 33 of 89 dystonia patients (37%) responded to trihexyphenidil, 13 of 53 (25%) responded to clonazepam, and 4 of 21 (19%) responded to baclofen. In conclusion, our large scale study suggested that zolpidem may be a therapeutic option for dystonia, particularly post-traumatic dystonia.

Efficacy of zolpidem for dystonia: a study among different subtypes.

Although there are some newly developed options to treat dystonia, its medical treatment is not always satisfactory. Zolpidem, an imidazopyridine agonist with a high affinity on benzodiazepine subtype receptor BZ1 (ω1), was found to improve clinical symptoms of dystonia in a limited number of case reports. To investigate what subtype of dystonia is responsive to the therapy, we conducted an open label study to assess the efficacy of zolpidem (5-20 mg) in 34 patients suffering from miscellaneous types of dystonia using the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS). Patients were entered into the study if they had been refractory to other medications as evaluated by BFMDRS (no change in the previous two successive visits). After zolpidem therapy, the scores in the patients as a whole were decreased from 7.2 ± 7.9 to 5.5 ± 5.0 (P = 0.042). Patients with generalized dystonia, Meige syndrome/blepharospasm, and hand dystonia improved in the scale by 27.8, 17.8, and 31.0%, respectively, whereas no improvement was found in cervical dystonia patients. Overall response rate among patients were comparable to that of trihexyphenidyl. Zolpidem may be a therapeutic option for generalized dystonia, Meige syndrome, and hand dystonia including musician's. Drowsiness was the dose-limiting factor.