A Novel Homozygous SCNN1B Variant Causing Severe Systemic Pseudohypoaldosteronism Type 1B in a Saudi Infant: A Case Report.

Pseudohypoaldosteronism type 1B (PHA1B) is a rare autosomal recessive disorder characterized by systemic resistance to aldosterone due to pathogenic variants in epithelial sodium channel (ENaC) subunit genes. We report an eight-month-old Saudi male infant, born to consanguineous parents, who initially presented at seven days of life with persistent hyperkalemia, hyponatremia, and metabolic acidosis. Despite aggressive medical management, including sodium supplementation, insulin-dextrose therapy, nebulized salbutamol, and peritoneal dialysis, electrolyte disturbances persisted. Whole-exome sequencing identified a novel homozygous likely pathogenic variant in the SCNN1B gene (NM_000336.2:c.1573C>T; p.Gln525*), confirming the diagnosis of systemic PHA1B.