Congenital hypoaldosteronism: the Visser-Cost syndrome revisited

Severe Aldosterone Synthase Deficiency in a 9-Day-Old Lebanese Boy: The Importance of Functional Studies to Establish Pathogenicity of Seemingly Benign Variants in CYP11B2

INTRODUCTION

Aldosterone synthase deficiency is a rare autosomal recessive disease characterized by vomiting, dehydration, salt wasting, life-threatening hyperkalemia in infancy, followed by failure to thrive. It results from pathogenic variants in CYP11B2.

CASE PRESENTATION

A boy, born in Montreal to Lebanese parents who are first cousins, was referred at 9 days of life for severe dehydration. A diagnosis of primary adrenal insufficiency was made, and treatment was started with fludrocortisone and hydrocortisone. Exome sequencing revealed a homozygous variant p.(Asn201Asp)(N201D) in CYP11B2. In silico, this variant was considered benign, but in vitro functional expression studies established it caused the severe aldosterone deficiency. It ended the diagnostic odyssey and allowed to safely stop hydrocortisone replacement.

CONCLUSION

If a gene variant co-segregates with a phenotype, in vitro functional studies are required even if in silico studies are negative.

Hyponatremia and Hyporeninemic-Hypoaldosteronism in a Pediatric Intensive Care Unit Patient

Hyponatremia is one of the most commonly encountered electrolyte abnormalities encountered in the pediatric world. Defined as a serum or plasma sodium less than 135 mEq/L, the etiology of hyponatremia is one that can typically be determined by performance of a thorough history. However, occasionally the etiology of a patient's hyponatremia is more elusive and determined only after laboratory evaluation. We present a 6-year-old girl with a complex medical history including spinal muscular atrophy, tracheostomy and ventilator dependence, who was admitted to the pediatric intensive care unit for treatment and evaluation of seizures with hyponatremia that was initially thought to be due to syndrome of inappropriate anti-diuretic hormone or cerebral salt wasting. However, during her hospital course, it was determined that the hyponatremia was more indicative of a rarer and much less common cause of hyponatremia, hyporeninemic-hypoaldosteronism. The physiological factors controlling serum sodium are reviewed, the etiologies of hyponatremia are presented and the treatment of hyporeninemic-hypoaldosteronism is discussed.

Congenital hyperreninemic hypoaldosteronism due to aldosterone synthase deficiency type I in a Portuguese patient - Case report and review of literature

Hyperreninemic hypoaldosteronism due to aldosterone synthase (AS) deficiency is a rare condition typically presenting as salt-wasting syndrome in the neonatal period. A one-month-old Portuguese boy born to non-consanguineous parents was examined for feeding difficulties and poor weight gain. A laboratory workup revealed severe hyponatremia, hyperkaliaemia and high plasma renin with unappropriated normal plasma aldosterone levels, raising the suspicion of AS deficiency. Genetic analysis showed double homozygous of two different mutations in the CYP11B2 gene: p.Glu198Asp in exon 3 and p.Val386Ala in exon 7. The patient maintains regular follow-up visits in endocrinology clinics and has demonstrated a favourable clinical and laboratory response to mineralocorticoid therapy. To our knowledge, this is the first Portuguese case of AS deficiency reported with confirmed genetic analysis.

Ashwagandha root in the treatment of non-classical adrenal hyperplasia

Congenital adrenal hyperplasia (CAH) is a well-characterised family of disorders of the adrenal cortices, resulting in varying degrees of cortisol, aldosterone and androgen deficiency or androgen excess, depending on the enzyme(s) affected and the degree of quantitative or functional enzyme deficit. Withania somnifera (WS), commonly known as Ashwagandha, is a medicinal plant that has been employed for centuries in ayurvedic medicine. Preclinical studies have shown that WS increases circulating cortisol levels and improves insulin sensitivity. We report the case of a 57-year-old woman with non-classical adrenal hyperplasia due to both 3-β-ol dehydrogenase deficiency and aldosterone synthase deficiency who was self-treated with WS for 6 months. After 6 months of treatment her serum 18-OH-hydroxycorticoserone, 17-OH-pregnenolone, corticosterone and 11-deoxycortisol decreased by 31%, 66%, 69% and 55%, respectively. The biochemical improvement was accompanied by a noticeable reduction in scalp hair loss.

Mutation THR-185 ILE is associated with corticosterone methyl oxidase deficiency type II

Two boys presenting with infection-triggered, life-threatening salt-loss and hyperkalaemia were published in 1991 in the European Journal of Pediatrics. In both boys, the diagnosis of corticosterone methyl oxidase (CMO) deficiency type II has been established on the basis of determinations of plasma and urinary steroids. We had the opportunity to perform a molecular genetic study in one of the two boys. This boy had an elevated plasma 18-hydroxycorticosterone/aldosterone ratio which is pathognomonic for CMO deficiency type II. Sequence analysis of the CYP11B2 gene revealed a homozygous single base exchange in codon 185 of CYP11B2 causing an amino acid substitution Thr185Ile.

CONCLUSION

A Thr185Ile mutation in the CYP11B2 gene was found in a patient with CMO deficiency type II. This mutation may change the secondary structure of the enzyme leading to its decreased activity.

Hereditary defect in biosynthesis of aldosterone: aldosterone synthase deficiency 1964-1997

We studied two of the three patients with a hereditary defect in the biosynthesis of aldosterone originally described by Visser and Cost in 1964. All three presented as newborns with salt-losing syndrome and failure to thrive. The original biochemical studies showed a defect in the 18-hydroxylation of corticosterone. According to the nomenclature proposed by Ulick, this defect would be termed corticosterone methyl oxidase deficiency type I. We measured plasma steroids in the untreated adult patients and performed molecular genetic studies. Aldosterone and 18-OH-corticosterone were decreased, whereas corticosterone and 11-deoxycorticosterone were elevated, thus confirming the diagnosis of corticosterone methyl oxidase deficiency type I. Cortisol and its precursors were in the normal range. Genetic defects in the gene CYP11B2 encoding aldosterone synthase (P450c11Aldo) have been described in a few cases. We identified a homozygous single base exchange (G to T) in codon 255 (GAG) causing a premature stop codon E255X (TAG). This mutation destroys a Aoc II restriction site. Digestion of a PCR fragment containing exon 4 of CYP11B2 (261 bp) with this restriction enzyme revealed in the two patients homozygous for the E255X mutation only a 261-bp fragment, whereas the heterozygous parents had three fragments (261 bp from the mutant allele and 194 and 67 bp from the wild-type allele). The mutant enzyme had lost the five terminal exons containing the heme binding site, and thus there was a loss of function enzyme. We conclude that the biochemical phenotype of these prismatic cases of congenital hypoaldosteronism can be explained by the patients genotype.