Acute Kidney Injury in a Previously Healthy 15-Year-Old Patient: A Subtle Presentation of Addison’s Disease

Introduction: Primary adrenal insufficiency (PAI), also known as Addison’s disease, is a disorder of the adrenal glands characterized by decreased levels of glucocorticoids and mineralocorticoids. It is a rare condition with a prevalence of 120 cases per million and is less frequently seen in the pediatric population. Here, we report a previously healthy 15-year-old patient with acute kidney injury (AKI) and PAI. Case Presentation: The patient was admitted to the hospital after findings of abnormal laboratory studies, which included an elevated BUN (53 mg/dL), creatinine (1.39 mg/dL), calcium (11.3 mg/dL), potassium (5.6 mmol/L), and hyponatremia (126 mmol/L). These were performed at an outpatient visit due to three-week history of back pain, fatigue and emesis. On admission, he had stable vital signs. Physical examination revealed generalized darkening of skin, more noticeable on the knuckles and palmar creases, with hyperpigmented patches in oral mucosa and both upper extremities. Although his renal function, serum potassium and calcium levels normalized after intravenous hydration with normal saline, hyponatremia (128 mmol/L) continued. His urine analysis and renal ultrasound were normal. Due to his hyperpigmentation and persistent hyponatremia, PAI was suspected. An ACTH stimulation test revealed that basal and stimulated serum cortisol levels were low, 2.6 mcg/dL and 2.9 mcg/dL, respectively. His plasma ACTH level was elevated at 1,625 pg/mL and serum aldosterone level was low at <4.0 ng/dL. These results were consistent with PAI. The patient’s hyponatremia resolved after receiving stress dose hydrocortisone. He was discharged home on hydrocortisone and fludrocortisone with endocrinology follow up. Discussion: PAI is well described in the literature, though reports in pediatrics vary. Patients may present with nonspecific symptoms such as unexplained weight loss, fatigue, diffuse abdominal pain, nausea, vomiting and muscular weakness. These symptoms may be of insidious onset, which often leads to delayed diagnosis. Physical signs include hypotension and hyperpigmentation. Characteristic biochemical findings are hyponatremia, hyperkalemia and hypoglycemia. Despite the electrolyte derangements, AKI is not a common presentation of PAI. There are only a few case reports associating these two diseases. In this case, his symptoms and abnormal electrolytes were initially considered to be the result of AKI of unknown origin. PAI only became a suspicion after a careful physical exam and persistent hyponatremia despite improvement of his AKI with fluid resuscitation. His low serum cortisol and aldosterone levels with elevated plasma ACTH confirmed the diagnosis of PAI. Conclusion: This case highlights a unique presentation of PAI in an adolescent. A timely diagnosis reduces the risk of unwanted and potentially life-threatening complications such as an Addisonian crisis.