Neuromuscular conditions associated with malignant hyperthermia in paediatric patients: A 25-year retrospective study
Ahmed K Bamaga1, Sheila Riazi2, Kimberly Amburgey1
1Division of Neurology, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
Abstract:
Malignant Hyperthermia (MH) is a rare pharmacogenetic syndrome that can be fatal and the risk of MH in non RYR1-related disorders is unknown. We conducted a retrospective study to determine the prevalence of neuromuscular disorders among patients with MH at our centre. Patients who were admitted to the Hospital for Sick Children during the study period of January 1, 1990 to April 1, 2015 with a CK level > 8000 IU/L, or who received dantrolene, or who had a clinical diagnosis of MH were included. Medical records of 166 patients who met the inclusion criteria were reviewed and 13 patients were identified with MH-like reactions. Nine patients were classified as having true MH after review of the anaesthesia record and genetic testing results were available for 7 patients, 5 of whom had mutations in RYR1. Of the four patients who had severe reactions to anaesthesia but did not meet the criteria for true MH, two had Duchenne muscular dystrophy (DMD). In this retrospective study over 25 years, RYR1 mutations were the most common cause of MH in our cohort, and of these, one third had an underlying neuromuscular diagnosis. Genetic testing of RYR1 is indicated for all patients with MH, and anaesthetic precautions should be considered for any child with symptoms of neuromuscular disease.
Insights
Malignant Hyperthermia (MH) is a rare genetic disorder. RYR1 gene mutations are the primary cause of MH, and many patients have underlying neuromuscular conditions.
Area of Science:
- Pharmacogenetics
- Neuromuscular Disorders
- Anesthesiology
Background:
- Malignant Hyperthermia (MH) is a rare, potentially fatal pharmacogenetic disorder.
- The risk of MH in patients with non-RYR1-related disorders is not well understood.
- Identifying underlying neuromuscular conditions in MH patients is crucial for management.
Purpose of the Study:
- To determine the prevalence of neuromuscular disorders in patients diagnosed with Malignant Hyperthermia.
- To investigate the association between RYR1 mutations and MH in a pediatric cohort.
- To inform anesthetic precautions for children with neuromuscular diseases.
Main Methods:
- Retrospective study of patients admitted between January 1, 1990, and April 1, 2015.
- Inclusion criteria: CK level > 8000 IU/L, dantrolene administration, or clinical MH diagnosis.
- Review of medical records, anesthesia records, and genetic testing results for RYR1 mutations.
Main Results:
- 166 patients met inclusion criteria; 13 had MH-like reactions.
- Nine patients were classified as true MH; 5/7 with genetic testing had RYR1 mutations.
- Two of four patients with severe anesthesia reactions (not true MH) had Duchenne muscular dystrophy (DMD).
Conclusions:
- RYR1 mutations are the most common cause of MH in this pediatric cohort.
- Approximately one-third of MH patients with RYR1 mutations had an underlying neuromuscular diagnosis.
- Genetic testing of RYR1 is indicated for all MH patients; anesthetic precautions are advised for children with neuromuscular disease symptoms.
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