顕著な左右差を呈したhypokalemic mypopathyの1例

A Case of Hypokalemic Myopathy Mimicking Hemiparesis

はじめに

　Hypokalemic myopathyは，体内からのカリウム（K）喪失あるいは摂取不足によって体内K含有量が低下し，creatine kinase（CK）などの筋原性酵素の上昇を伴って軀幹・四肢の筋力低下を生じる疾患である。通常，急性あるいは亜急性に発症し，筋力低下は下肢近位筋に始まり，上肢近位筋ないしは軀幹・頸部筋群に波及する^1－3）。今回，われわれは甘草を含む漢方薬の内服と飲酒を原因とし，一見すると片麻痺と捉えられるほどの顕著な左右差を呈したhypokalemic myopathyの1例を経験したので報告する。

Abstract

　We report the case of an 86-year-old female with licorice-induced hypokalemic myopathy.　For four years, she had been taking two kinds of Chinese medicines containing licorice.　The patient presented with difficulty in holding her head up and proximal-dominant tetraparesis with significant laterality.　In manual muscle tests, the right extremities showed grade 2/5 and the left extremities, grade 4/5.　The general reflexes were decreased, and the bilateral Chaddock's reflexes were repeatedly positive.　The sensory, cerebellar and autonomic systems were normal and discrete movements of all extremities were well preserved.　Laboratory tests showed elevated levels of CK (559IU/l), hypokalemia (1.6mEq/l), and metabolic alkalosis (pH 7.51, base excess 10.9mmol/l).　Magnetic resonance imaging showed mild compression of the spinal cord due to cervical spondylosis.　Electromyography revealed myopathic patterns in the deltoid muscle.　Steady clinical recovery was noted following treatment including cessation of licorice intake and administration of potassium supplementation.　Neck weakness, tetraparesis with laterality and Chaddock's reflexes were diminished.　We conclude that the pathologic reflex was caused by the aggravation of cervical spondylotic myelopathy due to neck weakness and that tetraparesis with laterality was caused by hypokalemic myopathy.