Aldosterone Synthase Deficiency Type I in a Neonate: Diagnostic, Genetic, and Therapeutic Insights From a Novel CYP11B2 Variant.

Aldosterone synthase deficiency (ASD), also known as corticosterone methyl oxidase deficiency, is a rare autosomal recessive disorder caused by inactivating mutations in the CYP11B2 gene (Cytochrome P450 family 11 subfamily B member 2). ASD is classified into two subtypes: type I (Corticosterone methyl oxidase (CMO) I) and type II (CMO II), with type I characterized by minimal or absent aldosterone production and a more severe clinical phenotype. We report the case of a four-year-old male child who presented neonatally with respiratory distress, hyperkalemia, and hyponatremia. Comprehensive workup, including genetic analysis, confirmed CMO I deficiency due to a novel homozygous CYP11B2 variant (NM_000498.3:c.239+1G>A), located at the donor splice site of intron 1. Early initiation of fludrocortisone and hydrocortisone led to favorable growth and development. This case underscores the importance of early recognition, genetic confirmation, and tailored therapy in managing rare neonatal electrolyte imbalances such as ASD type I.