Pain in SCN4A Mutated P.A1156T muscle sodium channelopathy-a postal survey.

INTRODUCTION: The p.A1156T mutation alters the function of the voltage-gated sodium channel Nav1.4 on the muscle sarcolemma, causing a channelopathy without overt myotonia or periodic paralysis but with myalgic pain. METHODS: A postal survey was conducted to assess the prevalence and characteristics of pain and related symptoms in individuals with the p.A1156T mutation. A specific questionnaire, intensity and interference subscales of the Brief Pain Inventory, pain drawing, Widespread Pain Index, quality of life (RAND-36), and the Beck Depression Inventory were completed. RESULTS: Twenty of 24 patients replied. Current pain was reported by 16 respondents; the other 4 had experienced pain previously. Most commonly, pain was widespread and exercise-induced. The severity and the impact of pain on daily life were considerable, although varied. DISCUSSION: This sodium channelopathy is another entity in the growing number of diseases causing widespread myalgic pain that resembles the pain seen in fibromyalgia syndrome. Muscle Nerve 57: 1014-1017, 2018.

Critical neural targets for (the level of) human consciousness: Arousal arrest and unconsciousness after sumatriptan administration.

BACKGROUND: Insufficient understanding of the mechanisms of consciousness can make unconsciousness a diagnostic challenge, directly effecting the treatment and the outcome of the patient. Consciousness is a product of brainstem arousal (wakefulness, the level of consciousness) and cortical information integration (awareness, the contents of consciousness). The thalamus serves as a critical hub in the arousal pathway. The nuclei within the internal medullary lamina, together with the associated thalamocortical connections, have been implicated as being especially important for human consciousness. CASE STUDY: A 17-year old male migraineur developed a sudden episode of unconsciousness after receiving a single dose of intranasal sumatriptan for the treatment of prolonged migraine-associated symptoms. Diffusion-weighted magnetic resonance imaging revealed a small bilateral thalamic infarction affecting the centromedian and parafascicular nuclei and the associated non-specific thalamocortical connections as the likely reason for the impairment of consciousness. With the exception of occasional fatigue due to a persistent lesion on the left thalamus, the patient experienced full recovery. Corresponding to the injury, diffusion tensor tractography imaging revealed a distinctive defect on the thalamocortical fibres originating from the left centromedian/parafascicular nuclei complex. CONCLUSIONS: The presented case offers an outstanding example of the importance of the arousal system and non-specific thalamocortical connectivity for normal waking consciousness.

Distal myopathies in Finnish patients.

Distal myopathies are a group of rare muscular dystrophies comprising more than 20 different genetic entities. The first distal myopathy in Finland, tibial muscular dystrophy, was identified more than 20 years ago. Muscle weakness predominantly affects the feet and hands, although variable weakness can be detected clinically and on muscle MRI in the proximal muscles in the later stages of the disease. Advanced molecular genetic techniques have enabled identification of several distinct distal myopathies in Finland. The clinical findings of different distal myopathies overlap, but there are also distinguishable differences that might help final genetic diagnostics.

Atypical phenotypes in titinopathies explained by second titin mutations.

OBJECTIVE: Several patients with previously reported titin gene (TTN) mutations causing tibial muscular dystrophy (TMD) have more complex, severe, or unusual phenotypes. This study aimed to clarify the molecular cause of the variant phenotypes in 8 patients of 7 European families. METHODS: Clinical, histopathological, and muscle imaging data of patients and family members were reanalyzed. The titin protein was analyzed by Western blotting and TTN gene by reverse transcription polymerase chain reaction (RT-PCR) and Sanger sequencing. RESULTS: Western blotting showed more pronounced C-terminal titin abnormality than expected for heterozygous probands, suggesting the existence of additional TTN mutations. RT-PCR indicated unequal mRNA expression of the TTN alleles in biopsies of 6 patients, 3 with an limb-girdle muscular dystrophy type 2J (LGMD2J) phenotype. Novel frameshift mutations were identified in 5 patients. A novel A-band titin mutation, c.92167C>T (p.P30723S), was found in 1 patient, and 1 Portuguese patient with a severe TMD phenotype proved to be homozygous for the previously reported Iberian TMD mutation. INTERPRETATION: The unequal expression levels of TTN transcripts in 5 probands suggested severely reduced expression of the frameshift mutated allele, probably through nonsense-mediated decay, explaining the more severe phenotypes. The Iberian TMD mutation may cause a more severe TMD rather than LGMD2J when homozygous. The Finnish patient compound heterozygous for the FINmaj TMD mutation and the novel A-band titin missense mutation showed a phenotype completely different from previously described titinopathies. Our results further expand the complexity of muscular dystrophies caused by TTN mutations and suggest that the coexistence of second mutations may constitute a more common general mechanism explaining phenotype variability.

[The expanding spectrum of LGMD--recently discovered disease genes are important also in Finnish patients]. / Hartia-lantiodystrofioiden (LGMD) kasvava kirjo--uusia tautigeenejä löytyy myös Suomesta.

Limb-girdle muscular dystrophies (LGMD) are autosomal disorders with a range of manifestations varying from almost asymptomatic late-onset patients to severe childhood onset forms. Recently identified disease genes explain the majority of LGMD cases in Finland. Prognosis, potential cardiac and respiratory complications and symptomatic treatment options differ in different LGMD subtypes. This means that the gold standard of diagnosis is the molecular genetic definition of the disease in each patient. Despite evolving sequencing techniques, the clinical, pathological, neurophysiological and imaging characterisation of patients will not become obsolete, but rather, even more important during the next years to enable targeted genetic diagnostics.

The enigma of 7q36 linked autosomal dominant limb girdle muscular dystrophy.

INTRODUCTION: Two families with autosomal dominant limb girdle muscular dystrophy (LGMD) have previously been linked to a locus on chromosome 7q36 10 years ago. The locus has been termed both LGMD1D and 1E, but because of lack of additional families to narrow down the linked region of interest, this disease has remained elusive. METHODS: A large Finnish family was clinically and genetically investigated. Laboratory parameters were determined, including creatine kinase (CK) value, neurographic and electromyography studies, cardiac and respiratory function examinations, muscle biopsies and muscle imaging by CT or MRI. RESULTS: Patients had onset of muscle weakness in the pelvic girdle between the fourth and sixth decades with an autosomal dominant pattern of inheritance. CK values were slightly elevated and electromyography was myopathic only. Muscle biopsies showed myopathic and/or dystrophic features with very minor rimmed vacuolation and protein aggregation findings. Molecular genetic analysis indicates linkage of the disease to the locus on chromosome 7q36 completely overlapping with the previously reported locus LGMD1D/E. DISCUSSION: Advancement towards the causative gene defect in the 7q36 linked disease needs new additional families to narrow the region of interest. The phenotype in the previously linked families has not been reported in full detail, which may be one reason for the shortage of additional families. A comprehensive clinical and morphological phenotype of chromosome 7q36 linked autosomal dominant LGMD with a restricted and updated 6.4 Mb sized haplotype is reported here.

Discontinuation of carbamazepine due to concerns of long-term consequences of enzyme induction.

OBJECTIVE: Treatment with carbamazepine (CBZ), a potent enzyme inducer, is known to affect the lipid profile, steroid, and vitamin D metabolism. Consequently, it has been postulated that patients on CBZ should be switched to noninducing antiepileptic drugs (AEDs). However, little is known about the seizure outcome following a CBZ switch in seizure-free patients. We aimed to address this issue using a controlled observational study design. METHODS: Fifty-eight patients taking CBZ for focal epilepsy were assessed for discontinuing CBZ treatment due to concerns of long-term adverse-effects; 34 discontinued its therapy and 24 continued with CBZ. Six-month seizure freedom was the primary end point. Furthermore, serum samples (total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglycerides, sex hormone-binding globulin (SHBG), free testosterone, and 25-hydroxyvitamin D levels from before and at least 3 months after discontinuation or continuation were obtained from all patients. RESULTS: Seizure-free patients had a 5-fold elevated odds of seizure recurrence if CBZ was discontinued (95% confidence interval [CI 0.51-49.3; p = 0.17). A significant decrease in serum levels of TC, LDL, HDL, and SHBG as well as a significant increase in that of free testosterone were found in the discontinuation group compared with those who continued CBZ. Nonsignificant changes in triglycerides and vitamin D levels were detected. SIGNIFICANCE: Discontinuation of CBZ in seizure-free patients seems to carry a moderate, but legitimate, risk of relapse. Conversely, our results indicate that CBZ might have unfavorable effects on serum levels of TC, LDL, HDL, SHBG, and free testosterone.

Predominantly myalgic phenotype caused by the c.3466G>A p.A1156T mutation in SCN4A gene.

OBJECTIVE: To characterize the clinical phenotype in patients with p.A1156T sodium channel mutation. METHODS: Twenty-nine Finnish patients identified with the c.3466G>A p.A1156T mutation in the SCN4A gene were extensively examined. In a subsequent study, 63 patients with similar myalgic phenotype and with negative results in myotonic dystrophy type 2 genetic screening (DM2-neg group) and 93 patients diagnosed with fibromyalgia were screened for the mutation. Functional consequences of the p.A1156T mutation were studied in HEK293 cells with whole-cell patch clamp. RESULTS: The main clinical manifestation in p.A1156T patients was not myotonia or periodic paralysis but exercise- and cold-induced muscle cramps, muscle stiffness, and myalgia. EMG myotonic discharges were detected in most but not all. Electrophysiologic compound muscle action potentials exercise test showed variable results. The p.A1156T mutation was identified in one patient in the DM2-neg group but not in the fibromyalgia group, making a total of 30 patients so far identified. Functional studies of the p.A1156T mutation showed mild attenuation of channel fast inactivation. CONCLUSIONS: The unspecific symptoms of myalgia stiffness and exercise intolerance without clinical myotonia or periodic paralysis in p.A1156T patients make the diagnosis challenging. The symptoms of milder SCN4A mutations may be confused with other similar myalgic syndromes, including fibromyalgia and myotonic dystrophy type 2.

Diagnostically important muscle pathology in DNAJB6 mutated LGMD1D.

INTRODUCTION: Limb girdle muscular dystrophies are a large group of both dominantly and recessively inherited muscle diseases. LGMD1D is caused by mutated DNAJB6 and the molecular pathogenesis is mediated by defective chaperonal function leading to impaired handling of misfolded proteins which normally would be degraded. Here we aim to clarify muscle pathology of LGMD1D in order to facilitate diagnostic accuracy. After following six Finnish LGMD1D families, we analysed 21 muscle biopsies obtained from 15 patients at different time points after the onset of symptoms. All biopsies were obtained from the lower limb muscles and processed for routine histochemistry, extensive immunohistochemistry and electron microscopy. RESULTS: Histopathological findings were myopathic or dystrophic combined with rimmed vacuolar pathology, and small myofibrillar aggregates. These myofibrillar inclusions contained abnormal accumulation of a number of proteins such as myotilin, αB-crystallin and desmin on immunohistochemistry, and showed extensive myofibrillar disorganization with excess of Z-disk material on ultrastructure. Later in the disease process the rimmed vacuolar pathology dominated with rare cases of pronounced larger pleomorphic myofibrillar aggregates. The rimmed vacuoles were reactive for several markers of defect autophagy such as ubiquitin, TDP-43, p62 and SMI-31. CONCLUSIONS: Since DNAJB6 is known to interact with members of the chaperone assisted selective autophagy complex (CASA), including BAG3 - a known myofibrillar myopathy causing gene, the molecular muscle pathology is apparently mediated through impaired functions of CASA and possibly other complexes needed for the maintenance of the Z-disk and sarcomeric structures. The corresponding findings on histopathology offer clues for the diagnosis.

Unique Exercise Lactate Profile in Muscle Phosphofructokinase Deficiency (Tarui Disease); Difference Compared with McArdle Disease.

INTRODUCTION: Glycogen storage disease V (GSDV, McArdle disease) and GSDVII (Tarui disease) are the most common of the rare disorders of glycogen metabolism. Both are associated with low lactate levels on exercise. Our aim was to find out whether lactate response associated with exercise testing could distinguish between these disorders. METHODS: Two siblings with Tarui disease, two patients with McArdle disease and eight healthy controls were tested on spiroergometric exercise tests with follow-up of venous lactate and ammonia. RESULTS: A late increase of lactate about three times the basal level was seen 10-30 min after exercise in patients with Tarui disease being higher than in McArdle disease and lower than in the controls. Ammonia was increased in Tarui disease. DISCUSSION: Our results suggest that follow-up of lactate associated with exercise testing can be utilized in diagnostics to distinguish between different GSD diseases.

PFKM gene defect and glycogen storage disease GSDVII with misleading enzyme histochemistry.

OBJECTIVE: To elaborate the diagnostic methods used as "gold standard" in one of the most common glycogen storage diseases (GSDs), Tarui disease (GSDVII). METHODS: Two siblings with disease suggestive of GSD underwent thorough clinical analysis, including muscle biopsy, muscle MRI, exercise tests, laboratory examinations, and whole-exome sequencing (WES). RESULTS: Both siblings had juvenile-onset exercise intolerance with cramping and infrequent myoglobinuria. Muscle biopsy showed extralysosomal glycogen accumulation, but because of normal phosphofructokinase histochemistry, GSDVII was thought to be excluded. However, WES revealed a causative homozygous PFKM gene defect, R39Q, in both siblings, establishing the diagnosis of GSDVII, which was confirmed by very low residual phosphofructo-1-kinase (PFK) enzyme activity in biochemical studies. CONCLUSIONS: We suggest that in patients with suspicion of GSD and extralysosomal glycogen accumulation, biochemical activity assay of PFK followed by molecular genetics should be performed even when enzyme histochemistry is normal.

Novel mutations in DNAJB6 gene cause a very severe early-onset limb-girdle muscular dystrophy 1D disease.

DNAJB6 is the causative gene for limb-girdle muscular dystrophy 1D (LGMD1D). Four different coding missense mutations, p.F89I, p.F93I, p.F93L, and p.P96R, have been reported in families from Europe, North America and Asia. The previously known mutations cause mainly adult-onset proximal muscle weakness with moderate progression and without respiratory involvement. A Finnish family and a British patient have been studied extensively due to a severe muscular dystrophy. The patients had childhood-onset LGMD, loss of ambulation in early adulthood and respiratory involvement; one patient died of respiratory failure aged 32. Two novel mutations, c.271T > A (p.F91I) and c.271T > C (p.F91L), in DNAJB6 were identified by whole exome sequencing as a cause of this severe form of LGMD1D. The results were confirmed by Sanger sequencing. The anti-aggregation effect of the mutant DNAJB6 was investigated in a filter-trap based system using transient transfection of mammalian cell lines and polyQ-huntingtin as a model for an aggregation-prone protein. Both novel mutant proteins show a significant loss of ability to prevent aggregation.

Spontaneous activity in electromyography may differentiate certain benign lower motor neuron disease forms from amyotrophic lateral sclerosis.

There is limited data on electromyography (EMG) findings in other motor neuron disorders than amyotrophic lateral sclerosis (ALS). We assessed whether the distribution of active denervation detected by EMG, i.e. fibrillations and fasciculations, differs between ALS and slowly progressive motor neuron disorders. We compared the initial EMG findings of 43 clinically confirmed, consecutive ALS patients with those of 41 genetically confirmed Late-onset Spinal Motor Neuronopathy and 14 Spinal and Bulbar Muscular Atrophy patients. Spontaneous activity was more frequently detected in the first dorsal interosseus and deltoid muscles of ALS patients than in patients with the slowly progressive motor neuron diseases. The most important observation was that absent fibrillations in the first dorsal interosseus muscle identified the benign forms with sensitivities of 66%-77% and a specificity of 93%. The distribution of active denervation may help to separate ALS from mimicking disorders at an early stage.

New immunohistochemical method for improved myotonia and chloride channel mutation diagnostics.

OBJECTIVE: The objective of this study was to validate the immunohistochemical assay for the diagnosis of nondystrophic myotonia and to provide full clarification of clinical disease to patients in whom basic genetic testing has failed to do so. METHODS: An immunohistochemical assay of sarcolemmal chloride channel abundance using 2 different ClC1-specific antibodies. RESULTS: This method led to the identification of new mutations, to the reclassification of W118G in CLCN1 as a moderately pathogenic mutation, and to confirmation of recessive (Becker) myotonia congenita in cases when only one recessive CLCN1 mutation had been identified by genetic testing. CONCLUSIONS: We have developed a robust immunohistochemical assay that can detect loss of sarcolemmal ClC-1 protein on muscle sections. This in combination with gene sequencing is a powerful approach to achieving a final diagnosis of nondystrophic myotonia.

Mutations affecting the cytoplasmic functions of the co-chaperone DNAJB6 cause limb-girdle muscular dystrophy.

Limb-girdle muscular dystrophy type 1D (LGMD1D) was linked to chromosome 7q36 over a decade ago, but its genetic cause has remained elusive. Here we studied nine LGMD-affected families from Finland, the United States and Italy and identified four dominant missense mutations leading to p.Phe93Leu or p.Phe89Ile changes in the ubiquitously expressed co-chaperone DNAJB6. Functional testing in vivo showed that the mutations have a dominant toxic effect mediated specifically by the cytoplasmic isoform of DNAJB6. In vitro studies demonstrated that the mutations increase the half-life of DNAJB6, extending this effect to the wild-type protein, and reduce its protective anti-aggregation effect. Further, we show that DNAJB6 interacts with members of the CASA complex, including the myofibrillar myopathy-causing protein BAG3. Our data identify the genetic cause of LGMD1D, suggest that its pathogenesis is mediated by defective chaperone function and highlight how mutations in a ubiquitously expressed gene can exert effects in a tissue-, isoform- and cellular compartment-specific manner.

Distinct distal myopathy phenotype caused by VCP gene mutation in a Finnish family.

Inclusion body myopathy with Paget disease and frontotemporal dementia (IBMPFD) is caused by mutations in the valosin-containing protein (VCP) gene. We report a new distal phenotype caused by VCP gene mutation in a Finnish family with nine affected members in three generations. Patients had onset of distal leg muscle weakness and atrophy in the anterior compartment muscles after age 35, which caused a foot drop at age 50. None of the siblings had scapular winging, proximal myopathy, cardiomyopathy or respiratory problems during long-term follow-up. Three distal myopathy patients developed rapidly progressive dementia, became bedridden and died of cachexia and pneumonia and VCP gene mutation P137L (c.410C>T) was then identified in the family. Late onset autosomal dominant distal myopathy with rimmed vacuolar muscle pathology was not sufficient for exact diagnosis in this family until late-occurring dementia provided the clue for molecular diagnosis. VCP needs to be considered in the differential diagnostic work-up in patients with distal myopathy phenotype.

Four new Finnish families with LGMD1D; refinement of the clinical phenotype and the linked 7q36 locus.

The objective is to refine the clinical and morphological phenotype and the chromosomal region of interest, in the recently reported 7q36 linked autosomal dominant limb-girdle muscular dystrophy (LGMD1 D/E), by describing four new informative Finnish families. Examinations of the patients included serum CK, neurophysiological studies, cardiac and respiratory function examinations, muscle biopsies and muscle imaging. DNA samples were analyzed by genotyping. Patients in all families had very similar phenotypes with onset of muscle weakness in the pelvic girdle muscles between the fourth and sixth decade, later involvement of the shoulder girdle, and marked walking difficulties in the eighth decade. Muscle biopsies showed myopathic and/or dystrophic features. Genotyping confirmed linkage to the same locus at chromosome 7q36 in all families by one identically segregating haplotype. The linked region was narrowed down from <6.3 to <3.4Mb. Sequencing of the genes in the area is ongoing, aiming to identify the genetic defect.