Hypercalcemia in an Infant With Pseudohypoaldosteronism Type 1

Abstract

Background: Pseudohypoaldosteronism type 1 (PHA1) is an aldosterone resistance syndrome due to insensitivity of target tissues to aldosterone action, with supraphysiologic aldosterone and renin levels. PHA1 presents usually in infancy and is divided into autosomal dominant (AD) and autosomal recessive (AR) form. A secondary form of PHA1 associated with UTI and/or renal malformations was described. In AD PHA1, salt loss is due to renal mineralocorticoid resistance while hyponatremia in AR PHA1 is caused by multi-organ salt loss. PHA1 has variable signs/symptoms associated with hyponatremia and hyperkalemia; thus, this clinical picture can be attributed to more common conditions such as dehydration, poor feeding, congenital adrenal hyperplasia. Clinical Case: A 5-month old male was admitted for airway evaluation. He was a 23-week gestation preemie, with chronic lung disease, failure to thrive. Patient was found to have hyponatremia, hyperkalemia, high FeNa of 1.3% (intrinsic renal disease) and elevated BUN/Cr (92/1.15). Renal US found echogenic kidneys with poor cortical medullary differentiation suggesting renal disease. Further evaluation noted high aldosterone (1700 ng/dL) and renin (400 ng/mL/hr) levels. He was placed on low protein formula to help optimize BUN level. Baby was diagnosed with secondary PHA1 due to renal disease and started on NaCl supplementation. This led to normalization of BUN, creatinine and improvement in electrolytes. Patient also had high serum calcium ranging from 11.1 to 12.0 mg/dL. Hyponatremia, hyperkalemia, hypercalcemia could be attributed to possible CAH, however state screen and ACTH stimulation test were normal. Further workup showed high 25-OH-vitamin D > 99 ng/mL, PTH 46.9 pg/mL, phosphorous 5.4 mg/dL and 1,25-OH-vitamin D 63.1 pg/mL. Urine Ca/cr ratio was 0.522. Vitamin D supplementation was stopped and daily total fluids increased. Subsequently, there was improvement in serum Ca at 10.9 mg/dL and 25-OH Vitamin D of 74 pg/mL. Next Generation Sequencing (NGS) was carried out, with a focus on the etiology of persisting hypercalcemia, including familial forms of hypercalcemia and Williams Syndrome. NGS revealed a likely pathogenic variant, c.2365 + 2T>C (p.?), in NR3C2, consistent with a diagnosis of AD PHA 1. Conclusion: This is a case of AD PHA1, marked by renal mineralocorticoid receptor resistance associated with persisting hypercalcemia. Initial hypercalcemia could be explained by hypervitaminosis D. It is important to note that electrolyte abnormalities, including persistent hypercalcemia, could be also secondary to the kidney disease found on renal US. There are only few reports of hypercalcemia in patients with PHA1 in the literature. In children with electrolyte abnormalities and failure to thrive, monitoring of serum and urine electrolytes would facilitate early accurate diagnosis and timely treatment.