Histopathologic and MRI findings in hypokalemic myopathy induced by glycyrrhizin

[Two cases with dropped head syndrome caused by hypokalemic myopathy]

We reported two women (78 and 85 years of age) with dropped head syndrome caused by hypokalemic myopathy restricted to the posterior cervical muscles. Both presented with relatively rapid onset of severe neck extensor weakness. Needle EMG demonstrated myogenic changes in the cervical paraspinal muscles and there were high intensity signals in the posterior cervical muscles on the neck MRI. Dropped head syndrome resolved in both patients as potassium normalized. One of the patients relapsed 11 months later with recurrent hypokalemia, but recovered rapidly with supplementation of potassium. Focal myopathy localized in the posterior cervical muscles due to hypokalemia should be considered as one of the possible causes of dropped head syndrome.

Giardiasis as a cause of hypokalemic myopathy in congenital immunodeficiency

Hypokalemic myopathy may occur in several infections. We report a case of severe and transient myopathy secondary to hypokalemia induced by chronic intestinal infection with Giardia lamblia in a patient with common variable hypogammaglobulinemia. Hypokalemic myopathy is documented by serum enzymes, electromyography (reduction in the number of voluntarily activated motor unit action potentials and an increase in polyphasic motor unit action potentials, and pathological changes (hematoxylin-eosin, ATPase staining). The case reported involves hypokalemic myopathy induced by giardiasis in a patient with primary immunodeficiency; the histopathological changes observed in a skin/muscle biopsy from this patient are described for the first time.