Myopathy in familial hypokalaemic periodic paralysis independent of paralytic attacks

Abstract

Case historie and muscle biopsy findings are reported on 2 members of a family suffering from hypokalemic periodic paralysis associated with permanent muscular weakness. The 1st patient, aged 9 yr, as well as her affected sibs, gave a history of a slight and slowly progressing impairment from early childhood on. At age 8 she exhibited slightly reduced muscle strength occasionally in the morning, with a frank paralytic attack only on 2 occasions. Physical examination revealed slight proximal muscle weakness, predominantly in the legs. Light microscopic examination as well as ultrastructural analysis of the biopsy revealed large vacuoles in many muslce fibers, mostly containing glycogen. The 2nd patient, a man aged 18 yr, never experienced a paralytic attack nor any fluctuation in muscle strength. Though his muscular strength was slightly below expectation, no frank paresis could be detected on examination. The EMG [electromyogram] revealed no abnormalities except for slight myopathic changes bilaterally in the adductor magnus. Light microscopic examination of the muscle biopsy showed no pathological changes. Accumulations of glycogen and secondary atrophy and disappearance of muscle fibrils were seen with the electron microscope. In this family, myopathic histological changes do not result from paralytic attacks.