From Bartter's syndrome to renal tubular acidosis in a patient with Hashimoto's thyroiditis: A case report
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Hashimoto's thyroiditis (HT) is an autoimmune disease that can cause the dysfunction of glands. Moreover, autoimmune disease is an under-recognized cause of several types of tubular dysfunction such as renal tubular acidosis (RTA), Gitelman's syndrome (GS), and Bartter's syndrome (BS). However, the potential mechanism of acquired BS and RTA associated with autoimmune diseases remains unclear. A 55-year-old female patient presented with numbness in both lower extremities for 6 months. She had a 2-year history of HT. Laboratory findings showed hypokalemia, metabolic alkalosis, and elevated plasma aldosterone concentration and renin activity. Urinary analysis revealed renal wasting of potassium, sodium, and chloride. Therefore, she was diagnosed as having HT and secondary BS and was treated with oral methylprednisolone, potassium chloride, and spironolactone. Two weeks later, her serum potassium levels restored to normal. After that, however, the patient was lost to follow-up. Two years later, she was re-hospitalized for progressive muscle weakness and quadriplegia. Laboratory results demonstrated severe hypokalemia, hyperchloremic metabolic acidosis, and inappropriate alkaline urine. Thus, distal RTA (dRTA) was confirmed, and she was prescribed potassium citrate and prednisone, resulting in the correction of hypokalemia and acid-base disturbance within 2 weeks after discharge. We report an HT patient who initially developed hypokalemic metabolic alkalosis and then developed metabolic acidosis within a few years. To our knowledge, this is the first report of two completely opposite acid-base disturbances associated with renal tubular diseases occurring consecutively in the same patient with HT. Our case may provide a valuable clue for exploring the mechanism of renal involvement in autoimmune diseases.