Dystrophic Myopathy of the Diaphragm with Recurrent Severe Respiratory Failure is Congenital Myasthenic Syndrome 11.

We here present the case of a patient with a congenital myasthenic syndrome (CMS) due to pathogenic variants in the RAPSN gene. During childhood he experienced recurrent episodes of respiratory failure during respiratory infections. This and other cases were reported as isolated dystrophy of the diaphragmatic musculature. In adulthood, whole exome sequencing revealed two heterozygous pathogenic variants in the RAPSN gene. This led to the revision of the diagnosis to rapsyn CMS11 (OMIM:616326, MONDO:0014588). EMG, muscle ultrasound and the revision of muscle biopsies taken in childhood support this diagnosis. After the revision of the diagnosis, treatment with pyridostigmine was started. This resulted in a reduction of fatigability and an improvement in functional abilities and quality of life.

Impaired oxygen utilization in skeletal muscle of CRPS I patients.

BACKGROUND: The purpose of this study was to evaluate oxygen extraction and utilization in end stage chronic complex regional pain syndrome type I (CRPS I) patients undergoing amputation and to relate these to muscle histology of the amputated limb. MATERIALS AND METHODS: In 25 patients with severe CRPS I requiring amputation of the affected limb venous blood samples and in 11 patients skeletal muscle specimens were analyzed. RESULTS: The mean venous oxygen saturation (S(v)O(2)) value (94.3% ± 4.0%) of the affected limb was significantly higher than S(v)O(2) values found in healthy subjects (77.5% ± 9.8%) pointing to a severely decreased oxygen diffusion or utilization within the affected limb. Histologic analysis showed a significant decrease of type I fibers and a significant increase of type IIB fibers. Ultrastructural investigations of soleus skeletal muscle capillaries revealed thickened endothelial cells and thickened basement membranes. Muscle capillary densities were decreased in comparison with literature data. High venous oxygen saturation levels were partially explained by impaired diffusion of oxygen due to thickened basement membrane and decreased capillary density. CONCLUSION: This study shows that venous oxygen saturation is significantly increased in chronic end stage CRPS I patients corresponding with impaired oxygen diffusion. The abnormal skeletal muscle findings points to severe disuse but only partially explain the impaired diffusion of oxygen; mitochondrial dysfunction seems a likely explanation in addition.

Muscle 3243A-->G mutation load and capacity of the mitochondrial energy-generating system.

OBJECTIVE: The mitochondrial energy-generating system (MEGS) encompasses the mitochondrial enzymatic reactions from oxidation of pyruvate to the export of adenosine triphosphate. It is investigated in intact muscle mitochondria by measuring the pyruvate oxidation and adenosine triphosphate production rates, which we refer to as the "MEGS capacity." Currently, little is known about MEGS pathology in patients with mutations in the mitochondrial DNA. Because MEGS capacity is an indicator for the overall mitochondrial function related to energy production, we searched for a correlation between MEGS capacity and 3243A-->G mutation load in muscle of patients with the MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes) syndrome. METHODS: In muscle tissue of 24 patients with the 3243A-->G mutation, we investigated the MEGS capacity, the respiratory chain enzymatic activities, and the 3243A-->G mutation load. To exclude coinciding mutations, we sequenced all 22 mitochondrial transfer RNA genes in the patients, if possible. RESULTS: We found highly significant differences between patients and control subjects with respect to the MEGS capacity and complex I, III, and IV activities. MEGS-related measurements correlated considerably better with the mutation load than respiratory chain enzyme activities. We found no additional mutations in the mitochondrial transfer RNA genes of the patients. INTERPRETATION: The results show that MEGS capacity has a greater sensitivity than respiratory chain enzymatic activities for detection of subtle mitochondrial dysfunction. This is important in the workup of patients with rare or new mitochondrial DNA mutations, and with low mutation loads. In these cases we suggest to determine the MEGS capacity.

The oxidative response in the chronic constriction injury model of neuropathic pain.

BACKGROUND: In the chronic constriction injury model of rat neuropathic pain, oxidative stress as well as antioxidants superoxide dismutase and reduced glutathione (GSH) are important determinants of neuropathological and behavioral consequences. Studies of the chronic constriction injury model observed (indirect) signs of inflammation. We, therefore, investigated the level of oxidative stress and antioxidant enzymes in skeletal muscle tissue of the rat hind paw and (jugular vein) plasma at d 7 after nerve injury. MATERIALS AND METHODS: The level of reactive oxygen and nitrogen species (RONS) was determined as a measure of oxidative stress. Reduced GSH levels and the ceruloplasmin/transferrin ratio were determined as measures of overall antioxidant activity. RONS and overall antioxidant activity were measured in skeletal muscle tissue of the hind paw and jugular vein plasma. The level of RONS in muscle was determined using spin trapping combined with electron paramagnetic resonance spectroscopy. Using electron paramagnetic resonance spectroscopy, we also determined plasma levels of transferrin and ceruloplasmin. GSH levels were determined using high-performance liquid chromatography. RESULTS: In skeletal muscle tissue, the level of RONS was lower in nerve-injured hind paws than in controls. The plasma level (jugular vein) of RONS did not differ between nerve-injured and control rats. In skeletal muscle tissue, the level of GSH was higher in nerve-injured hind paws than in controls. The ceruloplasmin/transferrin ratio tended to be higher in (jugular vein) plasma of nerve-injured rats as compared to controls. CONCLUSIONS: This study shows that, at d 7 after nerve injury, oxidative stress-induced changes are present also in skeletal muscle tissue of the rat hind paw. Our findings of a decreased level of RONS in combination with an increased level of the antioxidant GSH suggest that an overshoot of antioxidant activity overrules initial oxidative stress.

Early diagnosis of ALS: the search for signs of denervation in clinically normal muscles.

AIM AND METHODS: We prospectively investigated whether early diagnosis of amyotrophic lateral sclerosis (ALS) could be facilitated by demonstrating signs of denervation in a muscle of a clinical and electromyographical unaffected region. Muscle fibre conduction velocity (MFCV) was determined in 18 patients in whom the diagnosis ALS was considered but not established beyond a level of clinically possible ALS according to the revised El Escorial criteria. A muscle biopsy was obtained from the same muscle, to demonstrate neurogenic changes. The study followed the guidelines from the STARD initiative. RESULTS AND CONCLUSION: Results were analysed with respect to the final diagnosis. After a mean follow-up of 16 months, 9 patients developed probable or definite ALS. Sensitivity of abnormal MFCV for developing ALS was 89%. Muscle biopsy confirmed that denervation was the cause of abnormal MFCV. We concluded that MFCV can be used to detect denervation in muscles that show no clinical or electromyographical signs of lower motor neuron disease, and thus may contribute to early diagnosis of probable laboratory-supported ALS.

Severe congenital muscular dystrophy in a LAMA2-mutated case.

Clinical features and molecular data are described for a patient with undetectable expression of laminin alpha2 chain (merosin) and severe congenital muscular dystrophy. Molecular analysis of the LAMA2 gene revealed two previously un-described mutations. The patient achieved independent sitting at age 2, but lost head balance at age 7; he was never able to stand unsupported. Cerebral magnetic resonance imaging revealed diffuse hypomyelination in both cerebral hemispheres; electrophysiological assessment revealed progressive sensorimotor axonal polyneuropathy. Investigation of the primary molecular defect in congenital muscular dystrophy patients is important for genetic counseling, because the clinical features of the various forms overlap, and because significant laminin alpha2 chain reduction may occur in patients with primary defects in other genes.

Secondary mitochondrial dysfunction in propionic aciduria: a pathogenic role for endogenous mitochondrial toxins.

Mitochondrial dysfunction during acute metabolic crises is considered an important pathomechanism in inherited disorders of propionate metabolism, i.e. propionic and methylmalonic acidurias. Biochemically, these disorders are characterized by accumulation of propionyl-CoA and metabolites of alternative propionate oxidation. In the present study, we demonstrate uncompetitive inhibition of PDHc (pyruvate dehydrogenase complex) by propionyl-CoA in purified porcine enzyme and in submitochondrial particles from bovine heart being in the same range as the inhibition induced by acetyl-CoA, the physiological product and known inhibitor of PDHc. Evaluation of similar monocarboxylic CoA esters showed a chain-length specificity for PDHc inhibition. In contrast with CoA esters, non-esterified fatty acids did not inhibit PDHc activity. In addition to PDHc inhibition, analysis of respiratory chain and tricarboxylic acid cycle enzymes also revealed an inhibition by propionyl-CoA on respiratory chain complex III and alpha-ketoglutarate dehydrogenase complex. To test whether impairment of mitochondrial energy metabolism is involved in the pathogenesis of propionic aciduria, we performed a thorough bioenergetic analysis in muscle biopsy specimens of two patients. In line with the in vitro results, oxidative phosphorylation was severely compromised in both patients. Furthermore, expression of respiratory chain complexes I-IV and the amount of mitochondrial DNA were strongly decreased, and ultrastructural mitochondrial abnormalities were found, highlighting severe mitochondrial dysfunction. In conclusion, our results favour the hypothesis that toxic metabolites, in particular propionyl-CoA, are involved in the pathogenesis of inherited disorders of propionate metabolism, sharing mechanistic similarities with propionate toxicity in micro-organisms.

A case of neuromuscular mimicry.

Recognizing an ALS-mimic can be challenging. Here, we describe a patient with a slowly progressive dysarthria and dysphagia, with fasciculations of the tongue and general hyperreflexia, fulfilling the diagnostic criteria of 'clinical probable ALS'. Because of a non-conclusive EMG, a muscle biopsy was performed that surprisingly showed widespread nemaline rods. The clinical features and the histological findings were compatible with a sporadic late onset nemaline myopathy. Three years after initial presentation the patient died and post-mortem examination not only showed nemaline bodies in every muscle examined, but also revealed an unsuspected final diagnosis: sarcoid brainstem encephalitis. Nemaline rods can be found in various disorders, and neurosarcoidosis should be added to this list.

Novel mutations in three patients with LGMD2C with phenotypic differences.

Limb-girdle muscular dystrophy type 2C is an autosomal-recessive disorder caused by mutations in gamma-sarcoglycan encoding gene. This disease is characterized by childhood onset of progressive muscular dystrophy. Because of the clinical presentation, this disorder may be misdiagnosed as a dystrophinopathy. Two males (Patients A and B) from one Turkish family and one male (Patient C) from a Moroccan family had progressive walking disturbances for several years, exercise intolerance, and leg pains. Clinical examination revealed limb-girdle weakness and calf hypertrophy. Serum creatine kinase levels ranged from 1100 to 19000 U/L. The initial findings and course of the disease were less severe in Patient B compared with his brother (Patient A) at the same age. By means of immunohistochemistry on muscle biopsy all patients manifested reduced expression of alpha-, beta-, gamma-, and delta-sarcoglycans. DNA sequence analysis revealed a homozygous splice site mutation in exon 5 (IVS5+2T>C) in the Turkish family. In the patient from the Moroccan family a homozygous nonsense mutation in exon 2 (93G>A;Trp31X) was present. In conclusion, this report describes the clinical, histologic, and immunohistochemical characteristics of three children with limb-girdle muscular dystrophy type 2C. Two novel mutations in the gamma-sarcoglycan gene were present. We found phenotypic differences in two brothers.

Multiple oxidative phosphorylation deficiencies in severe childhood multi-system disorders due to polymerase gamma (POLG1) mutations.

Failure to thrive, feeding difficulties, variable forms of infantile epilepsy or psychomotor developmental delay and hypotonia were the most frequent clinical disease presentations in eight children with combined oxidative phosphorylation enzyme complex deficiencies carrying mutations in the polymerase gamma (POLG1) gene. Five out of eight patients developed severe liver dysfunction during the course of the disease. Three of these patients fulfilled the disease criteria for Alpers syndrome. Most children showed deficiencies of respiratory chain enzyme complexes I and III, in combination with complex II, complex IV and/or PDHc in muscle, whereas in fibroblasts normal enzyme activities were measured. All children carried homozygous or compound heterozygous mutations in the POLG1 gene, including two novel mutations in association with mtDNA depletion. Conclusion We suggest performing POLG1 mutation analysis in children with combined oxidative phosphorylation deficiencies in muscle, even if the clinical picture is not Alpers syndrome.

Null mutations and lethal congenital form of glycogen storage disease type IV.

Glycogen branching enzyme deficiency (glycogen storage disease type IV, GSD-IV) is a rare autosomal recessive disorder of the glycogen synthesis with high mortality. Two female newborns showed severe hypotonia at birth and both died of cardiorespiratory failure, at 4 and 12 weeks, respectively. In both patients, muscle biopsies showed deposits of PAS-positive diastase-resistant material and biochemical analysis in cultured fibroblasts showed markedly reduced glycogen branching enzyme activity. Direct sequencing of GBE1 gene revealed that patient 1 was homozygous for a novel c.691+5 g>c in intron 5 (IVS5+5 g>c). RT-PCR analysis of GBE1 transcripts from fibroblasts cDNA showed that this mutation produce aberrant splicing. Patient 2 was homozygous for a novel c.1643G>A mutation leading to a stop at codon 548 in exon 13 (p.W548X). These data underscore that in GSD-IV a severe phenotype correlates with null mutations, and indicate that RNA analysis is necessary to characterize functional consequences of intronic mutations.

Investigation of a family following fulminant malignant hyperthermia.

UNLABELLED: Malignant hyperthermia (MH) is a pharmacogenetic neuromuscular disorder triggered by inhalational anesthetics or succinylcholine. We studied in detail 24 relatives of a patient who died after experiencing MH. All steps of the screening procedure follow developments in testing for the diagnosis of MH susceptibility from 1984 until 2002. PATIENTS AND METHODS: : The screening procedure contained a general assessment and a clinical examination; creatine kinase (CK) measurement; genomic DNA isolation for linkage analysis and mutation screening; muscle samples were tested according to the in vitro contracture test protocol (IVCT) and examined histologically; and cultured skeletal muscle cells were used to examine the effect of halothane on the intracellular calcium concentration. RESULTS: : No correlation was found between IVCT results, serum CK, or abnormal findings after histologic examination, although CK elevation and the observation of cores seemed indicative for MH susceptibility in this family. Linkage analysis implicated RYR1 on chromosome 19q13.1 as the disease susceptibility locus in the family. The calcium response was found to be significantly different. CONCLUSION: : Following 3 decades of screening for MH, the gold standard for diagnosis remains the IVCT for detection of susceptibility to MH.

Muscle-fiber conduction velocity and electromyography as diagnostic tools in patients with suspected inflammatory myopathy: a prospective study.

Combinations of different techniques can increase the diagnostic yield from neurophysiological examination of muscle. In 25 patients with suspected inflammatory myopathy, we prospectively performed needle electromyography (EMG) and measured muscle-fiber conduction velocity (MFCV) in a single muscle, using a technique with direct muscle-fiber stimulation and recording. Results of MFCV were compared with final diagnosis, EMG, and needle muscle biopsy. Diagnostic accuracy of combined MFCV and EMG studies was 72%, compared to 60% for EMG alone. This improvement was due to a gain in specificity. The MFCV did not prove useful in discriminating inflammatory myopathy from other myopathies. Furthermore, we found a correlation of 92% between variability of MFCV and myopathic changes in muscle biopsy. We conclude that the utility of electrodiagnostic examination can be increased if EMG examination is combined with MFCV studies.

Congenital hypertrophic cardiomyopathy, cataract, mitochondrial myopathy and defective oxidative phosphorylation in two siblings with Sengers-like syndrome.

UNLABELLED: We describe two siblings with a Sengers-like syndrome, who presented with congenital hypertrophic cardiomyopathy, infantile cataract, mitochondrial myopathy, lactic acidosis and normal mental development. A mitochondrial adenine nucleotide translocator 1 (ANT1) defect was detected since the ANT1 protein was not detectable by immmunoblotting in muscle samples of the patients. Additionally to these features of classical Sengers syndrome (OMIM 212350), we found that the mitochondrial oxidative phosphorylation, measured by biochemical analysis, was severely compromised in skeletal muscle in both children. Biochemical and morphological analysis of the fibroblasts revealed normal results. The association of significantly decreased pyruvate oxidation rates, deficient energy production and decreased multiple mitochondrial enzyme-complex activities in the muscle samples of our patients is a new finding which differs from previous results in patients with Sengers syndrome. CONCLUSION: we recommend a muscle biopsy and the biochemical analysis of the oxidative phosphorylation system in patients with muscle hypotonia, cardiomyopathy and congenital or infantile cataract.

Concomitant dermatomyositis and myasthenia gravis presenting with respiratory insufficiency.

We report a 28-year-old woman with a history of chronic immune-mediated hepatitis, in whom the simultaneous manifestation of dermatomyositis and myasthenia gravis resulted in severe neck extensor weakness and subacute respiratory insufficiency, followed by proximal muscle weakness and external ophthalmoplegia. Radiological signs of a thymoma were absent. The distinguishing clinical, electrophysiological, and biopsy findings are discussed. We suggest that an underlying immunoregulatory disorder was present, explaining the occurrence of three rare immune-mediated diseases in one patient.