Neurology 2018 01 3;90(5):e412-e418. Epub 2018 Jan 3.
From 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.
Objective: To characterize the phenotype of patients with symptoms of periodic paralysis (PP) and ryanodine receptor () gene mutations.
Methods: Cases with a possible diagnosis of PP but additional clinicopathologic findings previously associated with 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 -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. analysis confirmed likely pathogenic variants in all 3 cases.
Conclusions: 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 -associated PP. We propose that clinicopathologic features suggestive of -related disorders should be sought in genetically undefined PP cases and that gene testing be considered in those in whom mutations in , and have already been excluded.