Extreme hyponatraemia with intact neurological outcome in a young child with Addison's disease

Renal involvement in adrenal insufficiency (Addison disease): can we always recognize it?

Addison disease is due to the destruction or dysfunction of the entire adrenal cortex. Nowadays, the causes of adrenal insufficiency are autoimmune disease for 70-90% and tuberculosis for 7-20%. Many typical signs and symptoms, such as hyponatremia, hyperkalaemia, or renal insufficiency can represent the reasons for a nephrology consultation, especially in conditions of urgency, and they can easily be confused with other causes. Moreover, the fact that in a short time range we have diagnosed the three cases described as a guide in this review, has aroused our attention as nephrologists on a disease in which we have probably already encountered but without recognizing it. The blood tests showed in all three patients severe electrolyte disorders and acute renal failure which will be discussed in their physiopathogenetic mechanisms. In a peculiar way, these alterations were not controlled with repolarizing solutions, fluid replacement and increased volemia, but only after steroid administration. In conclusion, in this review all the known pathogenic mechanisms causing disorders of nephrological interest in adrenal insufficiency are discussed.

Severe hyponatraemia with absence of hyperkalaemia in rapidly progressive Addison's disease

We present a case of rapidly progressing Addison's disease in adrenal crisis with severe hyponatraemia and absence of hyperkalaemia in a 10-year-old girl. She presented with 2 weeks of vomiting, fatigue and weight loss. Her serum electrolytes obtained 1 week prior to presentation were normal, except for mild hyponatraemia at 131 mmol/L, which dropped to 112 mmol/L on admission. She had normal serum potassium, low-serum osmolality, with elevated urine sodium and osmolality, indistinguishable from syndrome of inappropriate antidiuretic hormone (SIADH). Subsequently, Addison's disease was diagnosed on the basis of gingival hyperpigmentation and undetectable cortisol on adrenocorticotropic hormone stimulation test. She rapidly responded to stress dose hydrocortisone, followed by hydrocortisone and fludrocortisone replacement therapy. The absence of hyperkalaemia in the presence of severe hyponatraemia cannot rule out Addison's disease in children. The mechanism of hypo-osmolar hyponatraemia in primary adrenal insufficiency and clinical clues to differentiate it from SIADH are discussed.