Malignant hyperthermia in Japan: mutation screening of the entire ryanodine receptor type 1 gene coding region by direct sequencing.
BACKGROUND
Malignant hyperthermia (MH) is a disorder of calcium homeostasis in skeletal muscle triggered by volatile anesthetics or succinylcholine in susceptible persons. More than 100 mutations in the ryanodine receptor type 1 gene (RYR1) have been associated with MH susceptibility, central core disease, or both. RYR1 mutations may account for up to 70% of MH-susceptible cases. The authors aimed to determine the frequency and distribution of RYR1 mutations in the Japanese MH-susceptible population.


METHODS
The authors selected 58 unrelated Japanese diagnosed as MH-susceptible for having an enhanced Ca-induced Ca release rate from the sarcoplasmic reticulum on chemically skinned muscle fibers. They sequenced the entire RYR1 coding region from genomic DNA. Muscle pathology was also characterized.


RESULTS
Seven previously reported and 26 unknown RYR1 potentially pathogenic sequence variations were identified in 33 patients (56.9%). Of these patients, 48% had cores on muscle biopsy. The mutation detection rate was higher in patients with clear enhancement of Ca-induced Ca release rate (72.4%), whereas all patients with central core disease had RYR1 mutations. Six patients harbored potentially causative compound heterozygous sequence variations.


CONCLUSIONS
Distribution and frequency of RYR1 mutations differed markedly from those of the North American and European MH-susceptible population. Comprehensive screening of the RYR1 gene is recommended for molecular investigations in MH-susceptible individuals, because many mutations are located outside the "hot spots." Based on the observed occurrence of compound heterozygous state, the prevalence of a possibly predisposing phenotype in the Japanese population might be as high as 1 in 2,000 people.
Ibarra M
Carlos A
CA
Department of Neuromuscular Research, National Institute of Neuroscience, Tokyo, Japan.
Wu
Shiwen
S
Murayama
Kumiko
K
Minami
Narihiro
N
Ichihara
Yasuko
Y
Kikuchi
Hirosato
H
Noguchi
Satoru
S
Hayashi
Yukiko K
YK
Ochiai
Ryoichi
R
Nishino
Ichizo
I
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D008305:Malignant Hyperthermia / Q000235:genetics*; D008875:Middle Aged; D009154:Mutation; D020512:Myopathy, Central Core / Q000235:genetics; D016366:Open Reading Frames; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics*; D017422:Sequence Analysis, DNA
D019837:Ryanodine Receptor Calcium Release Channel