Mutations in CAV3 cause mechanical hyperirritability of skeletal muscle in rippling muscle disease.

Hereditary rippling muscle disease (RMD) is an autosomal dominant human disorder characterized by mechanically triggered contractions of skeletal muscle. Genome-wide linkage analysis has identified an RMD locus on chromosome 3p25. We found missense mutations in positional candidate CAV3 (encoding caveolin 3; ref. 5) in all five families analyzed. Mutations in CAV3 have also been described in limb-girdle muscular dystrophy type 1C (LGMD1C; refs. 6,7), demonstrating the allelism of dystrophic and non-dystrophic muscle diseases.

Creatine therapy in myophosphorylase deficiency (McArdle disease): a placebo-controlled crossover trial.

OBJECTIVE: To determine whether treatment with creatine can improve exercise intolerance in myophosphorylase deficiency (McArdle disease). DESIGN: Double-blind, placebo-controlled crossover study with oral creatine monohydrate supplementation. PATIENTS: Nine patients with biochemically and genetically proven McArdle disease were treated. INTERVENTION: Five days of daily high-dose creatine intake (150 mg/kg body weight) were followed by daily low-dose creatine intake (60 mg/kg). Each treatment phase with creatine or placebo lasted 5 weeks. MAIN OUTCOME MEASURES: The effect of treatment was estimated at the end of each treatment phase by recording clinical scores, ergometer exercise test results, phosphorus 31 nuclear magnetic resonance spectroscopy, and surface electromyography. RESULTS: Of 9 patients, 5 reported improvement of muscle complaints with creatine. Force-time integrals (P =.03) and depletion of phosphocreatine (P =.04) increased significantly during ischemic exercise with creatine. Phosphocreatine depletion also increased significantly during aerobic exercise (P =.006). The decrease of median frequency in surface electromyograms during contraction was significantly larger (P =.03) with creatine. CONCLUSION: This is the first controlled study indicating that creatine supplementation improves skeletal muscle function in McArdle disease.

Phenotypic variability in rippling muscle disease.

OBJECTIVE: To characterize the phenotype of hereditary rippling muscle disease (RMD) and to report the results of genetic linkage studies. BACKGROUND: RMD is a rare autosomal-dominant inherited muscle disorder. Individuals complain of muscle stiffness, exercise-induced muscle pain, and cramp-like sensations. The characteristic feature of RMD is increased mechanical muscle irritability, which is electrically silent in electromyographic examinations. METHODS: Forty-six individuals from two unrelated German kindreds with RMD were examined. Linkage analysis to the RMD locus on chromosome 1q41-q43 was performed. RESULTS: In kindred A, 15 individuals from four generations, and in kindred B, four individuals from three generations had clinical features of RMD. The most consistent clinical findings were percussion-induced rapid muscle contractions (PIRCs) and muscle mounding, which were present in all 19 affected individuals. Only 12 individuals exhibited muscle rippling, indicating that rippling is not always present in RMD. Twelve of 19 individuals had muscle-related complaints, primarily exertional cramps and stiffness. The mean age at the onset of complaints was 22 years (range, 5 to 54 years). Seven of 19 individuals showed only mechanical-induced muscle irritability but did not have muscular symptoms. Genetic analysis excluded linkage to the RMD locus on chromosome 1q4 in both kindreds. CONCLUSIONS: The phenotype of RMD is variable but generalized PIRCs are the most obvious and reliable clinical feature of RMD. Diagnostic criteria of RMD should include generalized PIRCs in addition to muscle mounding, rippling, and creatine kinase elevation.

A sporadic case of rippling muscle disease caused by a de novo caveolin-3 mutation.

OBJECTIVE: To determine the cause of sporadic rippling muscle disease (RMD) in a 24-year-old patient. BACKGROUND: RMD is a rare myopathy characterized by percussion-induced rapid muscle contractions (PIRC), muscle mounding, and rippling waves. We have recently found that autosomal dominant RMD is caused by mutations in the caveolin-3 gene (CAV3) on chromosome 3p25. Possibly, increased activity of neuronal nitric oxide synthase (nNOS) contributes to the clinical characteristics of increased mechanical muscle hyperexcitability. METHODS: Clinical examination, mutational analysis, and immunohistochemistry of muscle tissue were performed in a patient with sporadic RMD. RESULTS: The authors observed a de novo CAV3 missense mutation Arg26Gln. Immunohistochemistry showed reduced caveolin-3 surface expression in a muscle biopsy. In addition, the authors found normal sarcolemmal nNOS expression and a reduced expression of alpha-dystroglycan in muscle fibers. CONCLUSIONS: These data confirm that RMD is caused by CAV3 mutations. Moreover, there is evidence that CAV3 mutations may also be found in patients without a positive family history of RMD.

A common mutation (epsilon1267delG) in congenital myasthenic patients of Gypsy ethnic origin.

OBJECTIVE: Mutation analysis of the acetylcholine receptor (AChR) epsilon subunit gene in patients with sporadic or autosomal recessive congenital myasthenic syndromes (CMS). BACKGROUND: The nicotinic AChR of skeletal muscle is a neurotransmitter-gated ion channel that mediates synaptic transmission at the vertebrate neuromuscular junction. Mutations in its gene may cause congenital myasthenic syndromes. A recently described mutation in exon 12 of the AChR epsilon subunit (epsilon1267delG) disrupts the cytoplasmic loop and the fourth transmembrane region (M4) of the AChR epsilon subunit. METHODS: Forty-three CMS patients from 35 nonrelated families were clinically classified as sporadic cases of CMS (group III according to European Neuromuscular Centre consensus) and were analyzed for epsilon1267delG by PCR amplification and sequence analysis. RESULTS: The authors report the complete genomic sequence and organization of the gene coding for the epsilon subunit of the human AChR (accession number AF105999). Homozygous epsilon1267delG was identified in 13 CMS patients from 11 independent families. All epsilon1267delG families were of Gypsy or southeastern European origin. Genotype analysis indicated that they derive from a common ancestor (founder) causing CMS in the southeastern European Gypsy population. Phenotype analysis revealed a uniform pattern of clinical features including bilateral ptosis and mild to moderate fatigable weakness of ocular, facial, bulbar, and limb muscles. CONCLUSIONS: The mutation epsilon1267delG might be frequent in European congenital myasthenic syndrome patients of Gypsy ethnic origin. In general, patients (epsilon1267delG) were characterized by the onset of symptoms in early infancy, the presence of ophthalmoparesis, positive response to anticholinesterase treatment, and the benign natural course of the disease.

A G468-T AMPD1 mutant allele contributes to the high incidence of myoadenylate deaminase deficiency in the Caucasian population.

Myoadenylate deaminase deficiency is the most common metabolic disorder of skeletal muscle in the Caucasian population, affecting approximately 2% of all individuals. Although most deficient subjects are asymptomatic, some suffer from exercise-induced myalgia suggesting a causal relationship between a lack of enzyme activity and muscle function. In addition, carriers of this derangement in purine nucleotide catabolism may have an adaptive advantage related to clinical outcome in heart disease. The molecular basis of myoadenylate deaminase deficiency in Caucasians has been attributed to a single mutant allele characterized by double C to T transitions at nucleotides +34 and +143 in mRNA encoded by the AMPD1 gene. Polymerase chain reaction-based strategies have been developed to specifically identify this common mutant allele and are considered highly sensitive. Consequently, some laboratories preferentially use this technique over other available diagnostic tests for myoadenylate deaminase deficiency. We previously identified a G468-T mutation in one symptomatic patient who was only heterozygous for the common AMPD1 mutant allele. In this report, nine additional individuals with this compound heterozygous genotype are revealed in a survey of 48 patients with documented deficiency of skeletal muscle adenosine monophosphate deaminase and exercise-induced myalgia. Western blot analysis of leftover biopsy material from one of these individuals does not detect any immunoreactive myoadenylate deaminase polypeptide. Baculoviral expression of the G468-T mutant allele produces a Q156H substitution enzyme exhibiting labile catalytic activity. These combined results demonstrate that the G468-T transversion is dysfunctional and further indicate that AMPD1 alleles harboring this mutation contribute to the high incidence of partial and complete myoadenylate deaminase deficiency in the Caucasian population. Consequently, genetic tests for abnormal AMPD1 expression designed to diagnose patients with metabolic myopathy, and to evaluate genetic markers for clinical outcome in heart disease should not be based solely on the detection of a single mutant allele.

Pharmacological in-vitro studies in malignant hyperthermia in childhood.

In 91 children the caffeine-halothane test was performed according to the technique used by Britt et al and Kalow et al. The muscles investigated, 12 mm long and 2 to 3 mm in diameter, showed concentration dependent contractures to caffeine and a distinct potentiation after adding halothane. Compared to adults children above the age of 2 show a higher range for caffeine-induced contractures but infants below this age responded the strongest in range and average. While children with neuromuscular diseases usually revealed contractures less than average compared to the reference group there are special myopathies and muscle conditions which lead to a normal reaction to caffeine but increased ones to caffeine plus halothane. The reason for this remains unknown but the patients concerned should be treated like individuals with the proven trait for MH. Out of 22 patients being possibly MH susceptible [9] or having survived an anaesthetic complication [13] 4 showed decreased caffeine thresholds and increased contractures to caffeine plus halothane which is in accordance with MH susceptibility. Basically the pharmacological in-vitro test may reveal false negative results due to diseased muscle fibres or a shifted sensitivity of the contractile elements to calcium. Practically most important however is the inconvertible diagnosis of MH in a given patient, which in the very end will allow decision on the validity of the pharmacological test being used.

Lymphocyte capping in muscular dystrophies.

Since reports of lymphocyte capping in muscular dystrophies of various authors revealed controversial results, we investigated 47 patients and carriers with Duchenne or Becker-Kiener muscular dystrophy according to different methods. There was no significant reduction of cap formation compared to 64 healthy controls, both groups showing a mean of about 75% caps. Reduced numbers of caps, however, could be demonstrated in three otherwise healthy probands aged 70 years or more, two patients under interferon treatment, four patients under high dose methotrexate therapy as well as one patient with untreated chronic myeloic leukemia. Thus lymphocyte capping in our experience is far from being a valid method for carrier detection or prenatal diagnosis of muscular dystrophies.

Mitochondrial myopathies with necrotizing encephalopathy of the Leigh type.

Two patients with mitochondrial encephalomyopathy (MEP) serve to emphasize the variability of this group of diseases. Cerebral insults, mitochondrial cardiopathy, relapsing ileus, cerebral angioma, ataxia, and myoclonic seizures characterized the first case of an adult man with similar diseases in his family, interpreted as transitional form between mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) and myoclonus epilepsy associated with ragged red fibers (MERRF). The second patient, a floppy infant with cardiomyopathy and myoclonism, statomotoric and mental retardation showed combined defects in mitochondrial respiratory chain at NADH-CoQ reductase and cytochrome c oxidase and a deficiency of carnitine. In both patients neuropathologically criteria of Leigh's syndrome could be demonstrated in the cerebral cortex, in case 2 also clinically. The classificatory problems of the relationships between KSS, MELAS, MERRF, Leigh's as well as Alpers' syndromes are discussed.

Congenital myasthenic syndromes: clinical and genetic analysis of 18 patients.

Congenital myasthenic syndromes (CMS) are a group of rare gentic disorders in which neuromuscular transmission is compromised by a variety of mechanisms, other than autoimmunity. Recently, substantial progress has been made by the identification of mutations in acetylcholine receptor (AChR) genes which cause CMS. We report on the clinical and genetic analysis of 18 independent CMS patients. All patients were clinically classified as sporadic cases of CMS (group III according to ENMC consensus). In order to investigate the prevalence of AChR mutations in this group we analyzed structural domains of the AChR genes at strategically important sites - the channel pore-lining regions (M2 domains) of the alpha, beta and epsilon subunits, and the extracellular domain close the acetylcholine (ACh) binding site. All patients showed wild-type sequence in these regions, mutations were not detected. Therefore, we conclude, that point mutations in domains which are known to cause slow channel congenital myasthenic syndromes (SCCMS) are rare in group III-patients in Germany. Determining the genetic defects causing CMS may have implications for diagnosis and genetic counseling of CMS patients. Moreover, this may be important for the therapeutic management of CMS as some patients may profit form quinidine sulfate. Therefore, further efforts will be undertaken to elucidate the underlying defects of CMS.

Anesthesia in neuromuscular diseases.

Neuromuscular diseases raise a lot of anesthesia related problems. The first is the hitherto unknown disease discovered by an unexpected adverse reaction to anesthetics or/and muscle relaxants up to a life-threatening incident. A second problem is the probable, suspected or proven disposition to malignant hyperthermia in patients with other neuromuscular diseases. Furthermore, severe rhabdomyolysis can be induced in myopathic muscle by the application of succinylcholine alone or in combination with inhalational anesthetics resulting in hyperkalemia, myoglobinuria and CK-elevation, sometimes followed by cardiac arrest. Cardiomyopathy is a common feature in many neuromuscular diseases. All cardiodepressant agents must be avoided. Specific problems with muscle relaxants arise in myasthenia gravis and in the myotonias. In the later stages of severe neuromuscular diseases the main problem concerning anesthesia is respiratory failure. The individual risk of every patient has to be evaluated before anesthesia. Recommendations for the anesthetic management are given.

Quick scheme for evaluation of atomic charges in arbitrary aluminophosphate sieves on the basis of electron densities calculated with DFT methods.

It is demonstrated that unique and simple analytical functions are justified for the atomic charge dependences q of the T (T = Al, P) and O atoms of aluminophosphates (AlPOs) using DFT calculations with several basis sets, starting from STO-3G to 3-21G and 6-21G**. Three internal (bonds, angles, ...) coordinates for the charge dependences of the T atoms and four coordinates for the O are sufficient to reach a precision of 1.8% for the fitted q(Al), 1.0% for q(P), and 2.5% for q(O) relatively to the values calculated at any basis set level. The proposed strategy consists in an iterative scheme starting from charge dependences based on the neighbor's positions only. Electrostatic potential values are computed to illustrate the differences between the calculated and fitted charges in the considered AlPO models.

[Neuromuscular diseases 2: muscular dystrophies (MD)]. / Neuromuskuläre Erkrankungen (NME).

Traditionally, muscular dystrophies (MDs) are progressive, hereditary, and primarily degenerative myopathies. Nowadays, due to molecular biology, MDs are looked upon as clinically and genetically heterogeneous myopathies characterized by protein defects of muscle tissue resulting most often in muscle weakness. They are caused by gene mutations leading to a decrease of structural proteins or enzymes. The site of the primary defect and the protein function are different. The disorders are defined according to the underlying protein defect (dystrophinopathy, calpainopathy, and others). The gene or gene product are not yet known in all forms of MD (for example, facioscapulohumeral muscular dystrophy). Therefore, the nomenclature based on the protein defects and the term MD are used concurrently. Clinical symptoms, pathogenesis, diagnosis, therapy, prognosis, and possible prevention of the more frequent MDs are discussed: dystrophinopathies (Duchenne, Becker type), Emery-Dreifuss syndrome (3 forms), facioscapulohumeral MD, limb-girdle MD (17 forms), myotonic dystrophies (2 forms), and congenital MD (11 forms). This article highlights the significance of molecular analyses and the possible multisystemic symptoms in these myopathies.