Guidelines for molecular genetic detection of susceptibility to malignant hyperthermia{dagger}

A. Urwyler1, T. Deufel2, T. McCarthy3 and S. West4,*

1Departments of Anaesthesia and Research, Kantonsspital, University of Basel, CH-4031 Basel, Switzerland. 2Institute for Clinical Chemistry and Laboratory Diagnosis, University of Jena, D-07743 Jena, Germany. 3Department of Biochemistry, University College Cork, Cork, Republic of Ireland. 4Northern Genetics Service, Molecular Genetics Unit, Newcastle upon Tyne NE2 4AA, UK*Corresponding author

{dagger}This article is accompanied by Editorial III.

Accepted for publication: September 12, 2000

Abstract

Malignant hyperthermia (MH) is a potentially fatal pharmacogenetic disease triggered by several anaesthetic agents. The in vitro muscle contracture test (IVCT) is the standard test to establish an individual’s risk of susceptibility to MH. Clinical practitioners and geneticists of the European MH Group have agreed on the present guidelines for the detection of MH susceptibility using molecular genetic techniques and/or IVCT to predict the risk of MH.

Br J Anaesth 2001; 86: 283–7

Keywords: complications, malignant hyperthermia; genetic factors, molecular genetics

Malignant hyperthermia (MH) is a potentially fatal pharmacogenetic disease triggered by commonly used potent inhalation anaesthetics and/or succinylcholine. The in vitro muscle contracture test (IVCT) is the standard test to establish an individual’s risk of susceptibility to MH.1 The European MH Group has developed a standardized protocol for the IVCT and has initiated and fostered international collaborative molecular genetic studies to investigate the molecular basis of MH. Data from these studies demonstrate that MH displays a high level of locus heterogeneity. Thus, it is not feasible to diagnose MH susceptibility, and, more specifically, to exclude MH risk, on the basis of a simple genetic test alone. However, it is of utmost importance to avoid false MH-negative (MHN) diagnoses because of the potential risk of MH during general anaesthesia for these patients and their offspring. These general obstacles notwithstanding, there may be specific situations where genetic data provide additional diagnostic information or contribute information independent of IVCT. It is the purpose of this document to outline recommended procedures for the potential diagnostic use of such genetic findings depending on the different clinical situations that may arise.

Referrals

The usual route of entry for individuals into MH investigations follows a suspected MH crisis and referral of the patient to an MH Investigation Unit, where diagnostic procedures and genetic counselling should be performed according to Figure 1.



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Fig 1 Suggested route for MH susceptibility testing. IVCT=in vitro muscle contracture test; MHN=malignant hyperthermia negative; MHS=malignant hyperthermia susceptible.

 
IVCT

An IVCT is performed on the patient or, if the patient is too young or has not survived the anaesthetic event, his or her parents. If MH susceptibility status is confirmed by IVCT, then there is a clinical responsibility to offer the IVCT to the relatives of the index case, assuming autosomal dominant inheritance and starting with first-degree relatives.

Genetic investigations

Mutation analysis
At this stage, molecular genetic testing for causative mutations in the ryanodine receptor gene (RYR1) of the index case could lead to quicker results for the rest of the kinship. An up-to-date list of mutations that have been shown to directly alter RYRI caffeine or halothane sensitivity is shown in Table 1.


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Table 1 List of RYR1 mutations potentially causative for MH susceptibility (MHS) and central core disease (CCD). Residue numbering within the RYR1 nucleotide and amino acid sequence corresponds to the human RYR1 sequence according to Zorzato and colleagues18 (accession number J05200.1), updated according to Zhang and colleagues16 and Phillips and colleagues.19 Functional characterization of the RYR1 mutations on RYR1 channel activity have been performed by calcium photometry on myotubes and/or COS-7 or HEK cells transfected with RYR1 genes bearing the mutations20–24
 
Genetic analysis should be performed in, or only after consultation with an MH Investigation Unit. Once a causative mutation has been detected in the proband or index patient, it can be used to test relatives who have not yet been tested by the IVCT. Mutation carriers should consequently be regarded as susceptible to MH. However, family members who do not carry the mutation observed in the pedigree should still undergo IVCT investigation. The reason for such caution is the observation in several pedigrees investigated by members of the European MH Group of discordance between genetic and IVCT results, implicating a second MH susceptibility gene segregating in the kinship.2 3

Segregation analysis
Once the MH status of the extended pedigree (e.g. 10 informative meioses) has been determined by the IVCT, it may be possible to undertake genetic segregation analysis with markers close to known MH susceptibility loci. An up-to-date list of recommended markers and details of genetic modelling compiled by the European Malignant Hyperthermia Group, Genetics Section, is available on the internet (http://www.emhg.org).

Rarely, a single pedigree may be sufficiently large to establish linkage to a candidate locus with a high probability (lod score >3.0). In such a situation the question arises as to whether or not haplotype analysis can be used to assign MH status. Under these circumstances, individuals carrying the high-risk haplotype should be regarded as susceptible to MH even without confirmation by a positive IVCT. The converse is not true, that is, identification of the low-risk haplotype does not equate with MHN status and such individuals should have IVCT determination of their MH status.

In families where linkage to a candidate gene, RYR1 or another locus, is suggested but not firmly established (i.e. lod score <3.0) haplotype analysis for predictive testing is not appropriate due to the high level of locus heterogeneity in MH. In such families, however, it is desirable to search for unknown mutations in the suggested candidate gene for research purposes.

Failure to reach a lod score of +3.0 in a single family due to the occurrence of a single individual in whom there is recombination between the haplotype and IVCT-determined MH status will require closer scrutiny and possible reassessment of the genetic and bioassay results to attempt to resolve the basis of the discordance. For predictive diagnosis in such families, the more conservative estimation, i.e. the higher risk outcome (either the MH susceptibility test result from the IVCT or the high-risk haplotype) should be the basis for the clinical decision.

Appendix

MH Investigation Units in Europe
Austria

Prof. H. Gilly

Klinik für Anästhesie und allgemeine Intensivmedizin der Universität Wien

Spitalgasse 23

A-1090 Wien

Prof. W.W. Lingnau

Univ. Klinik für Anaesthesie und Allgemeine Intensivmedizin

Anichstrasse 35

A-6020 Innsbruck

Belgium

Prof. L. Heytens

Department of Intensive Care

Universitair Ziekenhuis Antwerpen

Wilrijkstraat 10

B-2650 Edegem

Denmark

Dr K. Glahn

The Danish Malignant Hyperthermia Register

Department of Anaesthesia

Herlev University Hospital

DK-2730 Herlev

France

Prof. R. Krivosic-Horber

Département d’Anesthésie Réanimation

Hôpital B

Centre Hospitalier Régional Universitaire

Bd. du Proffesseur J. Leclercq

F-59037 Lille

Prof. Y. Nivoche

Département d'Anesthésie

Hôpital Robert Debré

48 Bd. Serurier

F-75935 Paris Cedex 19

Germany

Prof. W. Mortier

Klinik für Kinder- und Jugendmedizin der Universität Bochum

St Josefs-Hospital

Alexandrinenstrasse 5

D-44791 Bochum

Priv.-Doz. Dr F. Wappler

University Hospital Eppendorf

Department of Anaesthesiology

Martinistrasse 52

D-20246 Hamburg

Prof. D. Olthoff

Klinik und Poliklinik für Anästhesiologie und Intensivtherapie der Universität Leipzig

Liebigstrasse 20a

D-04103 Leipzig

Dr I. Tzanova

Klinik für Anästhesie

Uniklinik Mainz

Langenbeckstrasse 1

D-55131 Mainz

Prof. F. Lehmann-Horn

Institut für angewandte Physiologie der Universität Ulm

Albert-Einstein-Allee 11

D-89081 Ulm

Dr M. Anetseder

Institut für Anästhesiologie der Universität Würzburg

Josef Schneider Strasse 2

D-97080 Würzburg

Iceland

Prof. S. Sigurdsson

Department of Physiology

University of Iceland

IS-101 Reykjavik

Ireland

Prof. J.J.A. Heffron

Department of Biochemistry

University College

Cork

Italy

Dr V. Tegazzin

Department of Anaesthesiology

Traumatic-Orthopaedic Hospital

Via Facciolati 71

I-35127 Padova

Prof. V. Brancadoro

Institute of Anaesthesiology

Università degli Studi di Napoli Frederico II

Via S. Pansini 5

I-80131 Napoli

Dr S. Cozzolino

Settore Biofarmacologico A.O. Cardarelli

Via S. Giacomo dei Capri 66

I-80131 Napoli

The Netherlands

Dr M. Snoek

Department of Anaesthesiology

CWZ, C40-01

PO Box 9015

N-6500 Nijmegen

Norway

Dr T. Fagerlund

Institute of Medical Genetics

Ullevål Sykehus

N-0407 Oslo

Sweden

Dr G. Islander

Department of Anaesthesia

University Hospital

S-221 85 Lund

Switzerland

Prof. A. Urwyler

Departement Anästhesie

Universitätskliniken

Kantonsspital

CH-4031 Basel

UK

Prof. F.R. Ellis

MH Investigation Unit

Clinical Sciences Building

St James’s University Hospital

Leeds LS9 7TF

Footnotes

* for the European Malignant Hyperthermia Group Back

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