Cracking the code of aldosterone synthase deficiency: bridging genetics and biochemistry: a case report.

Objective: Aldosterone synthase deficiency (ASD) is a rare autosomal recessive inherited disease with an overall clinical phenotype of failure to thrive, vomiting, severe dehydration, hyperkalemia, and hyponatremia. Mutations in the CYP11B2 gene encoding AS are responsible for the occurrence of ASD. Defects in CYP11B2 gene have only been reported in a limited number of cases worldwide. Due to this potential life-threatening risk, a comprehensive hormonal investigation followed by genetic confirmation is essential for the clinical management of offspring.

Methods: We report a case of a newborn who was found to have persistent hyponatremia, hyperkalemia, low aldosterone level, raised renin levels, normal cortisol, and normal 17 hydroxyprogesterone level, suggesting the diagnosis of isolated ASD.

Results: Genetic report was suggestive of isolated ASD caused by a novel base pair deletion in exon 3, homozygous CYP11B2 variant (chr8:g.142915123_142915125del; depth: 124x d) (p.Lys175del; ENST00000323110.2). After initial steps of rehydration and salt restoration, the child was started on oral tablet fludrocortisone. The child responded well and showed a good gain in growth and development.

Discussion: We elaborate on the biochemical and genetic work-up performed and describe potential pitfalls in CYP11B2 sequencing due to its homology to CYP11B1.