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- Broman, M, et al.
(författare)
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Malignant hyperthermia and central core disease causative mutations in Swedish patients.
- 2007
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Ingår i: Acta Anaesthesiologica Scandinavica. - : Wiley. - 0001-5172 .- 1399-6576. ; 51:Nov 1, s. 50-53
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Tidskriftsartikel (refereegranskat)abstract
- Background: Malignant hyperthermia (MH) susceptibility is a pharmacogenetic disorder of intracellular calcium homeostasis. In susceptible individuals, halogenated anaesthetics and/or suxamethonium may trigger an MH reaction. The diagnosis of MH susceptibility is made by an in vitro contracture test of biopsied muscle strips. Methods: In 27 MH susceptible (MHS) probands and four MH negative (MHN) probands, exons 17, 39, 40, 45 and 46 of the RYR1 gene were screened for MH causative mutations. In addition, in three patients with established central core disease (CCD), exons 17, 39, 40, 45 and 46 and exons 95, 100, 101 and 102 were screened for MH and CCD causative mutations. All screenings were performed by direct sequencing of the entire exons. Results: MH causative mutations were found in five of the 27 MHS probands (19%). CCD causative mutations were found in two of three CCD patients in the C-terminal exons. None of the CCD patients showed a mutation in N-terminal exon 17 or in the central exons. Conclusions: In a Swedish population, screening of N-terminal exon 17 and the central exons for MH causative mutations in the RYR1 gene covers 19% of families. Thus, other mutations must also be responsible for MH susceptibility in Sweden. Although the number of CCD patients in this study was small, screening of the C-terminal exons for CCD causative mutations seems to be a promising tool in the process of making a diagnosis.
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| 2. |
- Broman, M, et al.
(författare)
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Mutation screening of the RYR1-cDNA from peripheral B-lymphocytes in 15 Swedish malignant hyperthermia index cases.
- 2009
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Ingår i: British Journal of Anaesthesia. - : Elsevier BV. - 1471-6771 .- 0007-0912. ; 102:5, s. 642-649
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Malignant hyperthermia (MH), linked to the ryanodine receptor 1 gene (RYR1) on chromosome 19, is a potentially lethal pharmacogenetic disorder which may lead to a disturbance of intracellular calcium homeostasis when susceptible individuals are exposed to halogenated anaesthetics, suxamethonium, or both. Central core disease (CCD) is a rare dominantly inherited congenital myopathy allelic to MH-susceptibility. METHODS: In this study, 14 unrelated MH-susceptible probands and one CCD patient from Sweden were screened for mutations in the RYR1. Since the RYR1 is also expressed in B-lymphocytes, RYR1-cDNA was transcribed from total RNA extracted from white blood cells. RESULTS: We detected two known RYR1 mutations and two previously described unclassified sequence variants. In addition, six novel sequence variants were detected. All mutations or sequence variants were verified on genomic DNA. Seven of the probands did not show any candidate mutation, although the total coding region of RYR1 was sequenced. Segregation data in in vitro contracture tested family members of three probands support a causative role of three of the novel sequence variants. CONCLUSIONS: Our study contributes to the genetic aetiology of MH in Sweden, but also raises questions about the involvement of genes other than RYR1 since nearly half of the probands did not show any sequence variants in the total coding region of the RYR1.
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| 3. |
- Islander, Gunilla, et al.
(författare)
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Male preponderance of patients testing positive for malignant hyperthermia susceptibility.
- 2007
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Ingår i: Acta Anaesthesiologica Scandinavica. - : Wiley. - 0001-5172 .- 1399-6576. ; 51:5, s. 614-620
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Tidskriftsartikel (refereegranskat)abstract
- Malignant hyperthermia susceptibility is diagnosed using an in vitro contracture test (IVCT). In families in which the mutation is known, genetic tests are also available. The inheritance pattern is regarded as autosomal dominant, which predicts equal proportions of men and women affected. The aim of this study was to investigate whether there were sex differences in the diagnostic outcome of the 1407 patients tested for malignant hyperthermia in Sweden between 1985 and 2005. Methods: Information about sex, diagnosis, IVCT result and kinship was analysed. Comparisons were made between the two sexes. Probands and relatives were analysed separately in order to eliminate bias caused by the type of surgery performed in the two sexes. Results: Males, more than females, revealed a pathological outcome in IVCT. Amongst male relatives, the fraction of pathological outcome in IVCT was 0.70 [95% confidence interval (CI), 0.66-0.74]; the corresponding value for females was 0.40 (95% CI, 0.36-0.44). Conclusion: A significant difference was observed in the sex distribution of outcome of IVCT, with significantly more males revealing a pathological IVCT. This indicates the influence of one or several factors related to sex in the outcome of IVCT, for example different expression of calcium handling proteins in the sexes, a complex pattern of inheritance or unknown environmental factors.
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| 4. |
- Islander, Gunilla, et al.
(författare)
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Reproducibility of in vitro contracture test results in patients tested for malignant hyperthermia susceptibility.
- 2002
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Ingår i: Acta Anaesthesiologica Scandinavica. - : Wiley. - 0001-5172. ; 46:9, s. 1144-1149
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The in vitro contracture test (IVCT) is the golden standard to diagnose malignant hyperthermia susceptibility (MHS). A high reproducibility is important for a high validity of a test. METHODS: We have therefore analyzed IVCT in 838 patients, investigated in two laboratories. Each halothane and caffeine test was performed in two muscle strips. The test results were analyzed with respect to reproducibility of abnormal outcomes within pairs of tested muscle strips and size of contractures, thresholds and quality criteria. The patients were tested according to the European Malignant Hyperthermia Group protocol (EMHG). To fulfill quality criteria in the EMHG protocol the twitch height should be 10 mN (1 g) or more. For the caffeine test a minimum contracture of 50 mN (5 g) or more at 32 mmol l-1 caffeine could be used as an alternative quality criterion RESULTS: There was better reproducibility with larger contractures. The correlation between size of contractures and fraction of muscle strips with abnormal contractures was 0.77 or larger. Contractures < 5 mN (0.5 g) were reproducible in less than half of the tests. There was no difference in reproducibility or size of contractures between tests fulfillling all quality criteria and those not fulfillling these criteria. CONCLUSIONS: IVCT responses close to cut off limits, i.e. <5 mN (0.5 g) in the EMHG protocol, are less reproducible and must scientifically be considered as less reliable. The clinical cut off limits must remain unchanged for reasons of clinical safety. The outcome of quality measurements does not influence the test results.
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| 6. |
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| 7. |
- Vukcevic, Mirko, et al.
(författare)
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Functional Properties of RYR1 Mutations Identified in Swedish Patients with Malignant Hyperthermia and Central Core Disease
- 2010
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Ingår i: Anesthesia and Analgesia. - 1526-7598. ; 111:1, s. 185-190
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: A diagnosis of malignant hyperthermia susceptibility by in vitro contraction testing can often only be performed at specialized laboratories far away from where patients live. Therefore, we have designed a protocol for genetic screening of the RYR1-cDNA and for functional testing of newly identified ryanodine receptor 1 (RYR1) gene variants in B lymphocytes isolated from peripheral blood samples drawn at local primary care centers. METHODS: B lymphocytes were isolated for the extraction of RYR1-mRNA and genomic DNA and for establishment of lymphoblastoid B cell lines in 5 patients carrying yet unclassified mutations in the RYR1. The B lymphoblastoid cell lines were used to study resting cytoplasmic calcium concentration, the peak calcium transient induced by the sarco(endo)plasmic reticulum Ca-ATPase inhibitor thapsigargin, and the dose-dependent calcium release induced by the ryanodine receptor agonist 4-chloro-m-cresol. RESULTS: It was possible to extract mRNA for cDNA synthesis and to create B lymphocyte clones from all samples. All B lymphoblastoid cell lines carrying RYR1 candidate mutations showed significantly increased resting cytoplasmic calcium levels as well as a shift to lower concentrations of 4-chloro-m-cresol inducing calcium release compared with controls. CONCLUSIONS: Peripheral blood samples are stable regarding RNA and DNA extraction and establishment of lymphoblastoid B cell lines after transportation at ambient temperature over large distances by ordinary mail. Functional tests on B cells harboring the newly identified amino acid substitutions indicate that they alter intracellular Ca2+ homeostasis and are most likely causative of malignant hyperthermia. (Anesth Analg 2010;111:185-90)
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