Hyponatremia secondary to multiple etiologies: a case report.

We herein describe a rare case of hyponatremia that was aggravated by a burn injury. The patient was also found to have hypothyroidism, followed by SIADH, and finally CSWS, which showed complicated clinical features. A 68-year-old man was admitted for evaluation and treatment of a thermal burn. On admission, the patient was dehydrated, which was evidenced by physical signs. The patient had hyponatremia (serum Na 123 mmol/L) with high excretion of urinary sodium. Plasma AVP levels related to plasma osmolality were high. Plasma levels of renin and aldosterone were low, while the plasma ANP level was normal. However, there was no deficiency of mineralocorticoid or glucocorticoid. After admission, the hyponatremia worsened, and edema with hypoproteinemia developed. The patient was found to have hypothyroidism due to chronic thyroiditis. However, hyponatremia was not completely recovered with replacement of thyroid hormone. The hyponatremia was normalized by administration of DMC. The skin injury was treated with a skin graft. After DMC was discontinued, hyponatremia developed once again. However, this time, there was no inappropriate antidiuresis and the hyponatremia was normalized with the administration of fludrocortisone. These findings revealed that the hyponatremia in this patient may have been primarily due to CSWS. It was most likely exacerbated by hypothyroidism, burn injury, and SIADH caused by the infection. The patient showed physical signs of dehydration and edema. Furthermore, biochemical laboratory data were unable to distinguish between hypovolemia and non-hypovolemia. These complicated features were explained by multiple disorders