Addison's Disease Mimicking Cerebral Salt Wasting Syndrome: A Case of Severe Hyponatremia

Hyponatremia is a common electrolyte abnormality with varying degrees of severity.It can be asymptomatic if mild and can cause convulsions and coma if severe.Systematic investigation of hyponatremia helps to find out the etiology and proper management.Here, we are presenting the case of a 67-year-old man who presented with vomiting, hyperpigmentation, and hypovolemic hyponatremia due to Addison's disease.Evaluation of hyponatremia showed elevated urinary sodium as expected in Addison's disease, but there was hypouricemia with increased fractional excretion of uric acid suggestive of cerebral salt wasting syndrome.Even with the correct diagnosis, wrong medication interval can cause inadequate rise in serum sodium.Mild thyroid-stimulating hormone elevation can occur in untreated isolated Addison's disease.Addison's disease should always be considered in unexplained hyponatremia even if laboratory findings are suggestive of cerebral salt wasting syndrome.Hyponatremia in Addison's disease may respond poorly to hypertonic saline until glucocorticoid deficiency is corrected, and steroid and fluid replacement is essential and lifesaving.