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Updated: Jan 28, 2026
Crystal Structure of the N-terminal Domain of Ryanodine Receptor from Plutella xylostella
Published on: November 30, 2018
An unusual ryanodine receptor 1 (RYR1) phenotype: Mild calf-predominant myopathy
Manu Jokela1, Giorgio Tasca2, Anna Vihola2
1From the Neuromuscular Research Center (M. Jokela, S.L., J.P., B.U.), Department of Neurology, University Hospital and University of Tampere; Division of Clinical Neurosciences (M. Jokela), Department of Neurology, Turku University Hospital and University of Turku; Kiinamyllynkatu 4-8 (M. Jokela), Turku, Finland; Unità Operativa Complessa di Neurologia (G.T.), Dipartimento di Scienze dell'Invecchiamento, Neurologiche, Ortopediche e della Testa-Collo, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy; Folkhälsan Institute of Genetics and Department of Medical Genetics (A.V., P.-H.J., S.V., M. Johari, M.S.), Haartman Institute, University of Helsinki, Finland; Institute of Pediatric Neurology (E.M., M.P.), Catholic University School of Medicine, Rome, Italy; Department of Pathology (S.H.), Fimlab Laboratories, Tampere University Hospital, Finland; Metabolic and Neuromuscular Unit (M.D.), Meyer Hospital, Florence, Italy; Department of Pediatric Neurology (P.I.), Children's Hospital, University of Helsinki and Helsinki University Hospital; Department of Neurology (P.H.), Kuopio University Hospital and University of Eastern Finland; and Department of Neurology (B.U.), Vasa Central Hospital, Finland. mejoke@utu.fi.
Objective:
To identify the genetic defect causing a distal calf myopathy with cores.
Methods:
Families with a genetically undetermined calf-predominant myopathy underwent detailed clinical evaluation, including EMG/nerve conduction studies, muscle biopsy, laboratory investigations, and muscle MRI. Next-generation sequencing and targeted Sanger sequencing were used to identify the causative genetic defect in each family.
Results:
A novel deletion-insertion mutation in ryanodine receptor 1 (RYR1) was found in the proband of the index family and segregated with the disease in 6 affected relatives. Subsequently, we found 2 more families with a similar calf-predominant myopathy segregating with unique RYR1-mutated alleles. All patients showed a very slowly progressive myopathy without episodes of malignant hyperthermia or rhabdomyolysis. Muscle biopsy showed cores or core-like changes in all families.
Conclusions:
Our findings expand the spectrum of RYR1-related disorders to include a calf-predominant myopathy with core pathology and autosomal dominant inheritance. Two families had unique and previously unreported RYR1 mutations, while affected persons in the third family carried 2 previously known mutations in the same dominant allele.
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