There are two aspects to the diagnosis: the recognition of an acute episode of MH, and the identification of patients with susceptibility to MH. Susceptibility to MH is a sub-clinical condition, although patients may describe feeling uncomfortable exercising in the heat, and some patients may complain of muscle cramps.
Testing for susceptibility to MH by muscle contracture testing and/or genetic screening is part of basic health maintenance for families affected by MH. There can be discordance between genetic testing and muscle contracture testing results. For diagnostic purposes the results of muscle contracture testing should be relied upon. However, when a causative genetic variant is identified, a diagnosis of malignant hyperthermia susceptibility should be applied; in this case, muscle contracture testing is not required.
Key risk factors for MH include exposure to potent inhalation anaesthetic and/or succinylcholine (suxamethonium), known susceptibility to MH, a previous MH episode, and/or a positive family history.
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