Acquired Gitelman syndrome in a patient with primary Sjögren syndrome

Acquired Gitelman syndrome (GS) associated with Sjögren syndrome (SS) is rare, and the test to determine the pathophysiological state of acquired GS in patients with primary SS has not been reported previously. A 47-year-old woman with sicca complex presented to our clinic with intermittent muscle cramping and weakness involving both lower extremities over several months. Laboratory findings showed hypokalemic metabolic alkalosis, hypomagnesemia, and hypocalciuria, which met the criteria for GS. Diagnostic evaluation identified primary SS as the cause of the acquired GS. Light microscopic examination of renal tissue from the patient showed mild tubulointerstitial nephritis. Immunohistochemical staining of renal tissue showed the absence of the sodium-chloride cotransporter (NCCT) in the distal convoluted tubules. Incubation of the patient's serum with normal mouse kidney tissue showed a pattern of NCCT in the distal convoluted tubules similar to that of incubation of normal mouse kidney with the rabbit polyclonal anti-NCCT antibody. This is a rare case of acquired GS associated with primary SS, and our findings suggest the presence of circulating autoantibodies to NCCT.