Progressive myopathy in hyperkalemic periodic paralysis

Arch Neurol. 1990 Sep;47(9):1013-7.

Progressive myopathy in hyperkalemic periodic paralysis.

Bradley WG, Taylor R, Rice DR, Hausmanowa-Petruzewicz I, Adelman LS, Jenkison M, Jedrzejowska H, Drac H, Pendlebury WW.

Department of Neurology, University of Vermont School of Medicine, Medical Center Hospital, Burlington 05405.

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.

PMID: 2396930

Genotype-Phenotype Correlation & Therapy in HyperKPP

Genotype-phenotype correlation and therapeutic rationale in hyperkalemic periodic paralysis.
Neurotherapeutics. 2007 Apr;4(2):216-24.
Jurkat-Rott K, Lehmann-Horn F.
Department of Applied Physiology, Ulm University, Ulm, Germany.

Familial hyperkalemic periodic paralysis (PP) is a dominantly inherited muscle disease characterized by attacks of flaccid weakness and intermittent myotonia. Some patients experience muscle stiffness that is aggravated by cold and exercise, bordering on the diagnosis of paramyotonia congenita. Hyperkalemic PP and paramyotonia congenita are allelic diseases caused by gain-of-function mutations of the skeletal muscle sodium channel, Nav1.4, which is essential for the generation of skeletal muscle action potentials. In this review, the functional and clinical consequences of the mutations and therapeutic strategies are reported and the differential diagnoses discussed.

Also, the question is addressed of whether hyperkalemic PP is truly a different entity than normokalemic PP. Additionally, the differential diagnosis of Andersen-Tawil syndrome in which hyperkalemic PP attacks may occur will be briefly introduced. Last, because hyperkalemic PP has been described to be associated with an R83H mutation of a MiRP2 potassium channel subunit, evidence refuting disease-causality in this case will be discussed.

PMID: 17395131