Malignant hyperthermia

Malignant hyperthermia is an inherited susceptibility to a rapid, dangerous increase in skeletal-muscle metabolism triggered by certain anesthetics. The crisis can cause muscle rigidity, hyperthermia, and organ damage.

Ryanodine receptor 1: A calcium-release channel in skeletal-muscle cells, encoded by the RYR1 gene. Many cases involve altered RYR1 channels that release excessive calcium during anesthetic exposure.
Malignant hyperthermia crisis: An acute episode of uncontrolled skeletal-muscle metabolism triggered by certain anesthetics in a susceptible person. It is the emergency manifestation of the inherited susceptibility.
RYR1: A gene that encodes the ryanodine receptor 1 calcium channel in skeletal muscle. Pathogenic variants in this gene account for many inherited cases.
Neuroleptic malignant syndrome: A rare reaction to dopamine-blocking drugs marked by rigidity, altered mental state, and autonomic instability. It can resemble malignant hyperthermia but is associated with different drugs and mechanisms.
Sarcoplasmic reticulum: A specialized membrane network in muscle cells that stores and releases calcium. It is the calcium reservoir emptied abnormally during a malignant hyperthermia crisis.
Caffeine–halothane contracture test: A laboratory test that measures muscle-fiber contraction after exposure to caffeine and halothane. It can establish susceptibility when genetic testing does not identify a causative variant.
CACNA1S: A gene encoding a voltage-sensing component of skeletal-muscle excitation–contraction coupling. Rare variants in CACNA1S can also confer susceptibility.
Serotonin syndrome: A toxic state caused by excessive serotonergic activity, often after medication exposure or interaction. It can cause fever and muscle abnormalities, but its characteristic neuromuscular findings differ.
Excitation–contraction coupling: The process by which electrical signals in muscle trigger calcium release and contraction. Malignant hyperthermia disrupts this process by sustaining calcium release and muscle activation.
RYR1-related myopathy: A group of inherited muscle disorders caused by variants in the RYR1 gene. Some RYR1 variants can cause both muscle disease and susceptibility to anesthetic-triggered crises.

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