Related Experiment Video
Updated: Feb 16, 2026
Clinical Examination Protocol to Detect Atypical and Classical Scrapie in Sheep
Published on: January 19, 2014
Atypical periodic paralysis and myalgia: A novel RYR1 phenotype
Emma Matthews1, Christoph Neuwirth2, Fatima Jaffer2
1From the MRC Centre for Neuromuscular Diseases (E.M., F.J., R.S.S., D.F., M.P., D.R.R., K.S., H.H., E.H., R.Q., J.L.H., M.G.H.), Department of Molecular Neuroscience, UCL Institute of Neurology and National Hospital for Neurology and Neurosurgery, Queen Square, London, UK; Neuromuscular Diseases Unit/ALS Clinic (C.N.), Kantonsspital St. Gallen, Switzerland; Neurogenetics Unit (R.S., H.H.) and Department of Neuropathology (J.L.H.), National Hospital for Neurology and Neurosurgery, Queen Square, London, UK; Human Genetics Laboratory Genetica (R.S.), Zurich, Switzerland; Genetics Department (R.M.), Viapath, Guy's Hospital, London; Wellcome Trust Centre for Mitochondrial Research (A.S.), University of Newcastle, Framlington Place, Newcastle Upon Tyne, UK; Institute of Pathology (E.H.), Belfast Health and Social Care Trust, Northern Ireland; Department of Neurology (J.P.), John Radcliffe Hospital, Oxford, UK; Departments of Biomedicine and Anesthesia (S.T.), Basel University Hospital, Switzerland; Department of Life Sciences (S.T.), Microbiology and Applied Pathology Section, University of Ferrara, Italy; Department of Paediatric Neurology (H.J.), Neuromuscular Service, Evelina Children's Hospital, St. Thomas' Hospital; and Department of Basic and Clinical Neuroscience (H.J.), Institute of Psychiatry, Psychology and Neuroscience, and Randall Division of Cell and Molecular Biophysics (H.J.), Muscle Signalling Section, King's College, London, UK. emma.matthews@ucl.ac.uk.
Objective:
To characterize the phenotype of patients with symptoms of periodic paralysis (PP) and ryanodine receptor (RYR1) gene mutations.
Methods:
Cases with a possible diagnosis of PP but additional clinicopathologic findings previously associated with RYR1-related disorders were referred for a tertiary neuromuscular clinical assessment in which they underwent detailed clinical evaluation, including neurophysiologic assessment, muscle biopsy, and muscle MRI. Genetic analysis with next-generation sequencing and/or targeted Sanger sequencing was performed.
Results:
Three cases with episodic muscle paralysis or weakness and additional findings compatible with a RYR1-related myopathy were identified. The McManis test, used in the diagnosis of PP, was positive in 2 of 3 cases. Genetic analysis of known PP genes was negative. RYR1 analysis confirmed likely pathogenic variants in all 3 cases.
Conclusions:
RYR1 mutations can cause late-onset atypical PP both with and without associated myopathy. Myalgia and cramps are prominent features. The McManis test may be a useful diagnostic tool to indicate RYR1-associated PP. We propose that clinicopathologic features suggestive of RYR1-related disorders should be sought in genetically undefined PP cases and that RYR1 gene testing be considered in those in whom mutations in SCN4A, CACNA1S, and KCNJ2 have already been excluded.
Related Concept Videos
03:25The Periodic Table
01:21Antipsychotic Drugs: Typical and Atypical Agents
04:00Periodic Classification of the Elements
01:07Effective Value of a Periodic Waveform
The effective value of a periodic current represents the direct current (DC) that conveys the same average power to a resistor as the periodic current itself. This concept is crucial when assessing AC circuits. To determine the...
00:57The Periodic Table and Organismal Elements
01:27The Periodic Table and Organismal Elements
Periodic Table Provides Information...