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September 1990

Progressive Myopathy in Hyperkalemic Periodic Paralysis

Author Affiliations

From the Departments of Neurology and Neuropathology, Universities of Vermont, Burlington (Drs Bradley, Taylor, and Pendlebury), Warsaw (Poland) (Drs Hausmanowa-Petruzewicz, Jedrzejowska, and Drac), and Newcastle-Upon-Tyne (England) (Ms Jenkison), and Tufts-New England Medical Center, Boston, Mass (Drs Adelman and Rice). Dr Taylor is now with Mountain Neurological Center, PA, Asheville, NC; Dr Rice is now in private practice in Pomona, Calif.

Arch Neurol. 1990;47(9):1013-1017. doi:10.1001/archneur.1990.00530090091018

• A progressive degenerative myopathy has been well described in hypokalemic periodic paralysis but is not as widely recognized in hyperkalemic periodic paralysis. We studied four families with the latter disease in which some members developed a progressive myopathy. Episodes of paralysis were prolonged, lasting for months in some cases, and in one case paralysis was sufficiently severe to require ventilatory support. The progressive myopathy tended to develop at a time when attacks of paralysis were decreasing in frequency. Muscle biopsy specimens showed variability in fiber size, internal nuclei, and fibers with vacuoles. Electron microscopy showed myofibrillary degeneration and tubular aggregates. An abnormal biopsy specimen was more common in older patients. Our experience suggests that a progressive myopathy is as common in hyperkalemic periodic paralysis as it is in the hypokalemic disorder.