MON-373 Pseudohypoaldosteronism Type 1, a Masquerader: Case Study

Background: Pseudohypoaldosteronism (PHA) Type 1 usually present in the newborn period as failure to thrive, hyponatremia and hyperkalemia. The spectrum of manifestation however ranges from asymptomatic to severe. Initial presentation may be easily confused with more common disease process like poor feeding with inadequate calorie intake, dehydration, Congenital Adrenal Hyperplasia (CAH), adrenal insufficiency (AI), urinary tract abnormality and hypoaldosteronism. Patients with PHA Type 1 have supraphysiological aldosterone and renin levels appropriate for the electrolyte abnormality but ineffective due to an abnormality in mineralocorticoid receptor or epithelial sodium channel (ENaC). Clinical case: We present a Caucasian female who was admitted for failure to thrive. At 3 weeks of age, she was found to have lost 14.5% of birth weight. She was afebrile and there was no vomiting. She had hyperkalemia, hyponatremia, hypercalcemia, and mild transaminitis (Na 129mmol/L (134-142mmol/L), K 6.8mmol/L (4-6.2mmol/L), Cl 91mmol/L (96-110mmol/L), Ca 11.8mg/dl (9-10.9mg/dl), ALT 35unit/L (8-32 units/L) with increased urine output (6-6.5ml/kg/hr (4-5ml/kg/hr). Genital examination, newborn screen, ECG, renal US, thyroid function, 17-OH progesterone, and ACTH stimulation tests were normal. No family history of similar electrolyte abnormalities. Treatment with sodium containing IVF and kayexalate improved her electrolytes. Her diagnosis at discharge was inadequate calorie intake and dehydration. Increased calorie intake resulted in continuous weight gain and resolution of electrolyte abnormality at discharge (Na 137mmol/L, K 5.6mmol/L, Cl 97, Ca 10.8mg/dl). Despite improvement in weight gain and being asymptomatic, follow up outpatient monitoring of electrolyte levels showed persistent hyponatremia and hyperkalemia (Na 129 mmol/L, K 7.8mmol/L). No gastrointestinal symptoms or skin abnormalities. Given her electrolyte abnormalities, the differential diagnoses included SIADH, Adrenal Insufficiency and hypoaldosteronism. The diagnosis of PHA Type 1 was made based on increased aldosterone and renin levels (Aldosterone 1031ng/dl (5-90ng/dl), Renin 277pmol/L (2-37pmol/L). She was started on oral Nacl supplement and high dose fludrocortisone resulting in resolution of electrolyte abnormality. Genetic evaluation is underway. Conclusion: PHA Type 1 is a rare clinical entity that can masquerade as other more common causes of malnutrition and electrolyte abnormality. Delay in prompt diagnosis and treatment of PHA Type 1 can be associated with morbidity and mortality. Follow up monitoring of serum and urine electrolyte levels is important in children presenting with malnutrition and electrolyte abnormalities to enable early recognition and adequate treatment initiation.