[A case of Sjögren's syndrome presenting with hypokalemic myopathy due to renal tubular acidosis].

A 37-year-old woman was admitted to our university hospital because of severe flaccid quadriplegia. Her laboratory data, lip biopsy and muscle biopsy findings were compatible with hypokalemic myopathy due to renal tubular acidosis(RTA) type I associated with primary Sjögren's syndrome. Kidney biopsy revealed chronic tubulointerstitial nephritis(TIN), consisting of focal mononuclear cell infiltration with tubulitis, interstitial fibrosis and tubular atrophy. Immunohistochemical analysis of the renal biopsy specimens showed that the infiltrating mononuclear cells were predominantly CD8+T cells, and CD68+ cells(macrophages), whereas CD4+ T cells were fewer in number. Following potassium administration and alkali therapy, hypokalemia and metabolic acidosis were ameliorated and limb palsy gradually subsided. Finally, RTA improved with prednisolon and short term cyclophosphamide treatment without supplemental potassium and alkali therapy.