Aldosterone Synthase Deficiency Research Articles

Neonatal salt wasting syndrome: Aldosterone synthase deficiency caused by a new splicing variant in CYP11B2

Aldosterone synthase deficiency (ASD) is a rare autosomal recessive disorder involving isolated aldosterone deficiency without any compromise of other adrenal hormones. This condition manifests mainly in the neonatal period and in infants as a salt wasting syndrome with vomiting and failure to thrive. Due to its potentially life-threatening effects, ASD requires a careful and early diagnosis based on appropriate hormonal investigations in order to initiate adequate management: rehydration as well as salt and fludrocortisone supplementation. Genetic analysis of the CYP11B2 gene will confirm ASD in most cases. We report the case of a newborn with a typical clinical presentation associated with some uncommon phenotypic features (hyperhidrosis, liver injury). Furthermore, our patient carries a new CYP11B2 splicing variant to be added to the approximately 60 pathogenic or likely pathogenic variants already reported.

A Japanese girl with aldosterone synthase deficiency requiring fludrocortisone until 10 years of age.

A Japanese girl with aldosterone synthase deficiency requiring fludrocortisone until 10 years of age.

Identification of a Novel CYP11B2 Variant in a Family with Varying Degrees of Aldosterone Synthase Deficiency

Isolated aldosterone synthase deficiency is a rare autosomal recessive disorder caused by pathogenic variants in CYP11B2, resulting in impaired aldosterone synthesis. We report on a neonate with isolated aldosterone synthase deficiency caused by a novel homozygous CYP11B2 variant Chr8:NM_000498.3:c.400G>A p.(Gly134Arg). The patient presented shortly after birth with severe signs of aldosterone deficiency. Interestingly, segregation analysis revealed that the patient’s asymptomatic father was also homozygous for the CYP11B2 variant. Biochemical evaluation of the father indicated subclinical enzyme impairment, characterized by elevated aldosterone precursors. Apparently, this homozygous variant led to different clinical phenotypes in two affected relatives. In this manuscript we elaborate on the biochemical and genetic work-up performed and describe potential pitfalls in CYP11B2 sequencing due to its homology to CYP11B1.

Identification of a Novel CYP11B2 Variant in a Family with Varying Degrees of Aldosterone Synthase Deficiency

Isolated aldosterone synthase deficiency is a rare autosomal recessive disorder caused by pathogenic variants in CYP11B2, resulting in impaired aldosterone synthesis. We report on a neonate with isolated aldosterone synthase deficiency caused by a novel homozygous CYP11B2 variant Chr8:NM_000498.3:c.400G>A p.(Gly134Arg). The patient presented shortly after birth with severe signs of aldosterone deficiency. Interestingly, segregation analysis revealed that the patient's asymptomatic father was also homozygous for the CYP11B2 variant. Biochemical evaluation of the father indicated subclinical enzyme impairment, characterized by elevated aldosterone precursors. Apparently, this homozygous variant led to different clinical phenotypes in two affected relatives. In this manuscript we elaborate on the performed biochemical and genetic work-up and describe potential pitfalls of CYP11B2 sequencing due to its homology to CYP11B2.

Excessive bilateral adrenal hyperplasia associated with aldosterone synthase (CYP11B2) deficiency

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Isolated Aldosterone Deficiency Due to an Aldosterone Synthase Mutation: A Rare Cause of Life-Threatening Salt Wasting in Infancy

Purpose: Isolated hypoaldosteronism is a rare cause of salt wasting in infancy caused by the loss of activity of aldosterone synthase (AS), which is encoded by the CYP11B2 gene. This condition may be life-threatening, especially in newborns. Methods: We are reporting the case of a newborn male born to consanguineous parents, who presented at the age of 1 month with severe dehydration, vomiting, and hypotonia. Results: Lab studies showed severe hyponatremia, hyperkalemia, and metabolic acidosis. Hormonal assessment confirmed a normal corticotrope axis with severe deficiency in aldosterone. Genetic analysis revealed a novel mutation in the CYP11B2 gene in the highly conserved donor splice site of exon 3 and confirmed the isolated aldosterone deficiency. The patient was subsequently treated with fludrocortisone and sodium only, without hydrocortisone. Conclusion: AS deficiency is a rare inherited disease. There should be a high index of suspicion of cases with life-threatening salt-wasting in infancy as dramatic clinical improvements and good long-term prognosis can be achieved with timely replacement treatment.

Catch-up Growth and Discontinuation of Fludrocortisone Treatment in Aldosterone Synthase Deficiency.

Aldosterone synthase deficiency (ASD) caused by mutations in the CYP11B2 gene is characterized by isolated mineralocorticoid deficiency. Data are scarce regarding clinical and biochemical outcomes of the disease in the follow-up. Assessment of the growth and steroid profiles of patients with ASD at the time of diagnosis and after discontinuation of treatment. Children with clinical diagnosis of ASD were included in a multicenter study. Growth and treatment characteristics were recorded. Plasma adrenal steroids were measured using liquid chromatography-mass spectrometry. Genetic diagnosis was confirmed by CYP11B2 gene sequencing and in silico analyses. Sixteen patients from 12 families were included (8 females; median age at presentation: 3.1 months, range: 0.4 to 8.1). The most common symptom was poor weight gain (56.3%). Median age of onset of fludrocortisone treatment was 3.6 months (range: 0.9 to 8.3). Catch-up growth was achieved at median 2 months (range: 0.5 to 14.5) after treatment. Fludrocortisone could be stopped in 5 patients at a median age of 6.0 years (range: 2.2 to 7.6). Plasma steroid profiles revealed reduced aldosterone synthase activity both at diagnosis and after discontinuation of treatment compared to age-matched controls. We identified 6 novel (p.Y195H, c.1200 + 1G > A, p.F130L, p.E198del, c.1122-18G > A, p.I339_E343del) and 4 previously described CYP11B2 variants. The most common variant (40%) was p.T185I. Fludrocortisone treatment is associated with a rapid catch-up growth and control of electrolyte imbalances in ASD. Decreased mineralocorticoid requirement over time can be explained by the development of physiological adaptation mechanisms rather than improved aldosterone synthase activity. As complete biochemical remission cannot be achieved, a long-term surveillance of these patients is required.

Aldosterone signaling defect in young infants: single-center report and review

BackgroundAldosterone (Ald) is a crucial factor in maintaining electrolyte and water homeostasis. Defect in either its synthesis or function causes salt wasting (SW) manifestation. This disease group is rare, while most reported cases are sporadic. This study aimed to obtain an overview of the etiology and clinical picture of patients with the above condition and report our rare cases.MethodsA combination of retrospective review and case studies was conducted at the Pediatric Endocrine unit of The First Affiliated Hospital Sun Yat Sen University from September 1989 to June 2020.ResultsA total of 187 patients with SW were enrolled, of which 90.4% (n = 169) were diagnosed with congenital adrenal hyperplasia (CAH). SW type 21-hydroxylase deficiency accounted for 98.8% (n = 167) of CAH diagnosis, while 1.2% (n = 2) was of lipoid CAH. Non-CAH comprised 9.6% (n = 18) of the total patients whose etiologies included SF-1 gene mutation (n = 1), X-linked adrenal hypoplasia congenita (n = 9), aldosterone synthase deficiency (ASD, n = 4), and pseudo-hypoaldosteronism type 1 (PHA1, n = 1). Etiologies were not identified in three patients. All of patients with ASD and PHA1 exhibited SW syndrome in their early neonatal period. DNA sequencing showed mutations of CYP11B2 for P1-P4 and NR3C2 for P5. P1 and P2 were sibling brothers affected by compound heterozygous mutations of c.1121G > A (p.R374Q) and c.1486delC p.(L496fs); likewise, P4 was identified with compound heterozygous mutations of c.1200 + 1G > A and c.240–1 G > T; meanwhile P3 demonstrated c.1303G > A p.(G435S) homozygous mutation in CYP11B2 gene. Lastly, P5 showed c.1768 C > T p.(R590*) heterozygous mutation in the NR3C2 gene.ConclusionEtiology of infant with aldosterone defect was mostly congenital. Renal and adrenal imaging are recommended to exclude renal causes. If clinical picture is suggestive, normal plasma Ald in early infancy cannot rule out aldosterone insufficiency.

Aldosterone synthase (CYP11B2) deficiency among Palestinian infants: Three novel variants and genetic heterogeneity.

Aldosterone synthase deficiency (ASD) is a rare potentially life-threatening genetic disorder that usually presents during infancy due to pathogenic variants in the CYP11B2 gene. Knowledge about CYP11B2 variants in the Arab population is scarce. Here, we present and analyze five Palestinian patients and their different novel pathogenic variants. Data on clinical presentation, electrolytes, plasma renin activity, and steroid hormone levels of five patients diagnosed with ASD were summarized. Sequencing of the CYP11B2 gene exons was followed by evolutionary conservation analysis and structural modeling of the variants. All patients were from highly consanguineous Palestinian families. The patients presented at 1-4 months of age with recurrent vomiting, poor weight gain, hyponatremia, hyperkalemia, and low aldosterone levels. Genetic analysis of the CYP11B2 gene revealed three homozygous pathogenic variants: p.Ser344Profs*9, p.G452W in two patients from an extended family, and p.Q338stop. A previously described pathogenic variant was found in one patient: p.G288S. We described four different CYP11B2 gene pathogenic variants in a relatively small population. Our findings may contribute to the future early diagnosis and therapy for patients with ASD among Arab patients who present with failure to thrive and compatible electrolyte disturbances.

Molecular Analysis of the CYP11B2 Gene in 62 Patients with Hypoaldosteronism Due to Aldosterone Synthase Deficiency.

Isolated congenital hypoaldosteronism presents in early infancy with symptoms including vomiting, severe dehydration, salt wasting, and failure to thrive. The main causes of this rare autosomal recessive disorder is pathogenic variants of the CYP11B2 gene leading to aldosterone synthase deficiency. To investigate the presence of CYP11B2 pathogenic variants in a cohort of patients with a clinical, biochemical, and hormonal profile suggestive of aldosterone synthase deficiency. Clinical and molecular study. Tertiary academic Children's Hospital, Center for Rare Pediatric Endocrine Diseases. Sixty-two patients (56 unrelated patients and 6 siblings), with hypoaldosteronism and their parents, underwent CYP11B2 gene sequencing after its selective amplification against the highly homologous CYP11B1 gene. In silico analysis of the identified novel variants was carried out to evaluate protein stability and potential pathogenicity. CYP11B2 gene sequencing revealed that 62 patients carried a total of 12 different pathogenic CYP11B2 gene variants, 6 of which are novel. Importantly, 96% of the 56 patients carried the previously reported p.T185I variant either in homozygosity or in compound heterozygosity with another variant. The 6 novel variants detected were: p.M1I, p.V129M, p.R141Q, p.A165T, p.R448C, and the donor splice site variant of intron 8, c.1398 + 1G > A. Molecular diagnosis was achieved in 62 patients with aldosterone synthase deficiency, the largest cohort thus far reported. Six novel genetic variants were identified as possibly pathogenic, extending the spectrum of reported molecular defects of the CYP11B2 gene.

Analysis of novel heterozygous mutations in the CYP11B2 gene causing congenital aldosterone synthase deficiency and literature review

Aldosterone synthase deficiency (ASD) is a rare autosomal recessive disorder characterized by severe hyperkalemia, salt loss, vomiting, severe dehydration and failure to thrive. ASD is a life-threatening electrolyte imbalance in infants resulting from mutations in CYP11B2. We described ASD in a Chinese male infant with vomiting, poor feeding and failure to thrive. He was mildly dehydrated, with a weight of 6 kg (−3.45 SDS) and length of 67 cm (−3.10 SDS). Laboratory tests showed hyponatremia (119 mmol/L), serum potassium 5.4 mmol/L, low plasma aldosterone and plasma renin activity (PRA) levels. Next-generation sequencing of his DNA revealed compound heterozygous mutations in CYP11B2, a known variant c.1391_1393delTGC (p.Leu464del, rs776404064) and a novel variant c.1294delA (p.Arg432Glyfs*37). The HEK-293T expression system was used to investigate the variants, demonstrating negligible aldosterone synthesis compared with WT CYP11B2. The patient started fludrocortisone and subsequently gained 3.2 kg of weight and normalized serum sodium (137 mmol/L). We further reviewed reported cases of ASD, summarizing clinical features and CYP11B2 mutations; missense and nonsense mutations are most frequent. Fludrocortisone treatment is essential for ASD, and the need for mineralocorticoid replacement wanes with age; eventually, therapy can be discontinued for many affected children. Our study broadens the ASD phenotypic spectrum and shows the efficiency of next-generation sequencing for patients with atypical clinical manifestations.

MON-268 A Rare Case of Primary Hypoaldosteronism in a Newborn

BACKGROUND: Primary aldosterone synthase deficiency (ASD) is a rare but potentially life-threatening cause of mineralocorticoid deficiency primarily due to a defect in CYP11B2, which encodes aldosterone synthase. There are two types of ASDs, both resulting in primary hypoaldosteronism, but due to differences in blockade of the terminal oxidation step, are distinguished by low 18-hydroxycorticosterone (18-OHC) in Type 1 and elevated 18-OHC in Type 2. With a wide variation in clinical severity and presentation, few cases of ASD have been reported. CLINICAL CASE: A 10-day old full term male infant born to unrelated parents of European descent presented with weight loss, poor feeding and dehydration, in the setting of hyponatremia (Na 127 mM, ref 131-145 mM) and hyperkalemia (K 8 mM, ref 3.2-6 mM). He had normal genitalia and no hyperpigmentation on exam. A cosyntropin stimulation test resulted in a cortisol of 19 μg/dL. Electrolytes transiently improved with normal saline but worsened after fluids were discontinued. Oral NaCl was initiated at a dose of 4 mEq/kg/day and titrated to 6 mEq/kg/day. Aldosterone levels while hyponatremic were inappropriately low (<35 ng/dL, ref <218 ng/dL) with elevated plasma renin activity (PRA) of 112 ng/mL/hr (ref 0.25-5.82 ng/mL/hr), consistent with primary hypoaldosteronism. On day 14 of life, fludrocortisone was started at 0.05 mg/day and increased to 0.2 mg/day until Na and K levels normalized. At 20 days of life he was discharged, only to return 3 days later with isolated hyperkalemia (K 6.4 mM), PRA elevation to 80 ng/mL/hr, and lethargy. Prior 18-OHC and corticosterone levels returned significantly low at <26 ng/dL and <40 ng/dL respectively, consistent with a diagnosis of Type 1 ASD. Subsequently, fludrocortisone was increased to 0.3 mg/day and NaCl to 8 mEq/kg/day. At 6 months, the infant continues to do well though growth velocity remains slightly impacted. However, due to suppressed PRA levels and hypertension on exam, fludrocortisone was reduced to 0.05 mg/day and NaCl to 4.5 mEq/kg/day. Given the rarity of Type 1 ASD, he was referred for genetic counseling to obtain molecular confirmation. CONCLUSION: This is a rare case of Type 1 ASD diagnosed in early infancy based on inappropriately low 18-OHC and aldosterone levels during times of hyponatremia or hyperkalemia requiring high doses of mineralocorticoid and salt replacement in the first few months of life. While ASD is generally considered less severe than CAH, it can present with recurrent dehydration, salt wasting and failure to thrive, and be lethal if not recognized promptly. Despite timely treatment, growth retardation can still occur. Long term follow-up is needed to better understand the natural history of ASD, though clinical severity may decrease with age. As it is not included in newborn screening, this case highlights the importance of suspecting ASD in infants with hyponatremia and hyperkalemia.

SAT-069 A Case of Congenital Hypoaldosteronism Due to Aldosterone Synthase Deficiency Misdiagnosed as Classic Congenital Adrenal Hyperplasia

Background: The clinical presentation of congenital hypoaldosteronism due to aldosterone synthase (aka corticosterone methyloxidase; CMO) deficiency varies with age and infants present with signs/symptoms of isolated mineralocorticoid deficiency. Classic congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21OHD) is characterized by combined glucocorticoid, mineralocorticoid deficiency and androgen excess. Clinical Case: A 6.8 y/o Female was referred for genetic testing for classic 21OHD CAH. Past History: Birth weight/length: 7.9 lbs/20 inches at term, uncomplicated pregnancy. Normal female genitalia. She presented within the 1st week of life with poor feeding and poor weight gain. Newborn screen - normal. Inpatient admission at 1 month for failure to thrive. Initial workup significant for Na 127 mg/dL (135 - 145), K 6.5 mg/dL (3.4 - 5.3), mildly elevated random 17hydroxyprogesterone (17OHP) 241 ng/dL (32 - 139) and cortisol 11.6 mcg/dL. She was diagnosed with CAH and initiated on hydrocortisone and fludrocortisone therapy. Medications: Hydrocortisone 2.5 mg twice daily (6.3 mg/m2/day), fludrocortisone 50 mcg daily. Family History: Non-contributory, mid-parental height 154.9 cm. Physical exam: Height 115.6 cm (20th %ile), weight 19.8 kg (18th %ile), BP 109/65 mmHg (95th/ 84th %ile). Well-appearing with no cushingoid features. Genital/pubertal exam: Prepubertal, normal female external genitalia. Laboratory tests: ACTH stimulation test was performed which showed - 0min: 17OHP 19 ng/dL, Cortisol 8 mcg/dL; 60min: 17OHP 155 ng/dL (<1000), Cortisol 23.4 mcg/dL (normal response >18), ruling out the diagnosis of classic 21OHD CAH. Hydrocortisone was discontinued. Further workup (holding fludrocortisone for 48hrs) showed mildly elevated plasma renin activity 3.5 ng/mL/hr (0.8 - 2), low aldosterone 1.8 ng/dL (3.5 - 124), normal 18-hydroxycorticosterone 11 ng/dL (6 - 85). 18-hydroxycorticosterone/aldosterone ratio 6.1 (ratio <10) - suggesting the diagnosis of CMO type I deficiency (1). Targeted genetic testing for CYP11B2 revealed a novel homozygous frameshift alteration in exon 3: p.Phe157Serfs*108 (c.451_469dup), a pathogenic variant predicted to lead to protein truncation and loss of function. Conclusions: This case demonstrates that the clinical presentation of isolated mineralocorticoid deficiency often overlaps features of combined glucocorticoid and mineralocorticoid deficiency. Normal newborn screen along with absence of virilization in a female infant should alert a clinician to consider isolated mineralocorticoid axis defects. The gold standard ACTH stimulation test should be performed to rule out classic CAH and avoid unnecessary glucocorticoid replacement and its long-term side effects. Reference: 1. Root AW, Disorders of aldosterone synthesis, secretion, and cellular function. Curr Opin Pediatr. 2014 Aug;26(4):480-6.

MECHANISMS IN ENDOCRINOLOGY: Rare defects in adrenal steroidogenesis.

Congenital adrenal hyperplasia (CAH) is a group of genetic disorders of adrenal steroidogenesis that impair cortisol synthesis, with compensatory increases in ACTH leading to hyperplastic adrenals. The term 'CAH' is generally used to mean 'steroid 21-hydroxylase deficiency' (21OHD) as 21OHD accounts for about 95% of CAH in most populations; the incidences of the rare forms of CAH vary with ethnicity and geography. These forms of CAH are easily understood on the basis of the biochemistry of steroidogenesis. Defects in the steroidogenic acute regulatory protein, StAR, disrupt all steroidogenesis and are the second-most common form of CAH in Japan and Korea; very rare defects in the cholesterol side-chain cleavage enzyme, P450scc, are clinically indistinguishable from StAR defects. Defects in 3β-hydroxysteroid dehydrogenase, which also causes disordered sexual development, were once thought to be fairly common, but genetic analyses show that steroid measurements are generally unreliable for this disorder. Defects in 17-hydroxylase/17,20-lyase ablate synthesis of sex steroids and also cause mineralocorticoid hypertension; these are common in Brazil and in China. Isolated 17,20-lyase deficiency can be caused by rare mutations in at least three different proteins. P450 oxidoreductase (POR) is a co-factor used by 21-hydroxylase, 17-hydroxylase/17,20-lyase and aromatase; various POR defects, found in different populations, affect these enzymes differently. 11-Hydroxylase deficiency is the second-most common form of CAH in European populations but the retention of aldosterone synthesis distinguishes it from 21OHD. Aldosterone synthase deficiency is a rare salt-losing disorder. Mild, 'non-classic' defects in all of these factors have been described. Both the severe and non-classic disorders can be treated if recognized.

Congenital primary adrenal insufficiency and selective aldosterone defects presenting as salt-wasting in infancy: a single center 10-year experience.

BackgroundSalt-wasting represents a relatively common cause of emergency admission in infants and may result in life-threatening complications. Neonatal kidneys show low glomerular filtration rate and immaturity of the distal nephron leading to reduced ability to concentrate urine.MethodsA retrospective chart review was conducted for infants hospitalized in a single Institution from 1st January 2006 to 31st December 2015. The selection criterion was represented by the referral to the Endocrinology Unit for hyponatremia (serum sodium <130 mEq/L) of suspected endocrine origin at admission.ResultsFifty-one infants were identified. In nine infants (17.6 %) hyponatremia was related to unrecognized chronic gastrointestinal or renal salt losses or reduced sodium intake. In 10 infants (19.6 %) hyponatremia was related to central nervous system diseases. In 19 patients (37.3 %) the final diagnosis was congenital adrenal hyperplasia (CAH). CAH was related to 21-hydroxylase deficiency in 18 patients, and to 3β-Hydroxysteroid dehydrogenase (3βHSD) deficiency in one patient. Thirteen patients (25.5 %) were affected by different non-CAH salt-wasting forms of adrenal origin. Four familial cases of X-linked adrenal hypoplasia congenita due to NROB1 gene mutation were identified. Two unrelated girls showed aldosterone synthase deficiency due to mutation of the CYP11B2 gene. Two unrelated infants were affected by familial glucocorticoid deficiency due to MC2R gene mutations. One girl showed pseudohypoaldosteronism related to mutations of the SCNN1G gene encoding for the epithelial sodium channel. Transient pseudohypoaldosteronism was identified in two patients with renal malformations. In two infants the genetic aetiology was not identified.ConclusionsEmergency management of infants presenting with salt wasting requires correction of water losses and treatment of electrolyte imbalances. Nevertheless, the differential diagnosis may be difficult in emergency settings, and sometimes hospitalized infants presenting with salt-wasting are immediately started on steroid therapy to avoid life-threatening complications, before the correct diagnosis is reached. Physicians involved in the management of infants with salt-wasting of suspected hormonal origin should remember that, whenever practicable, a blood sample for the essential hormonal investigations should be collected before starting steroid therapy, to guide the subsequent diagnostic procedures and in particular to address the analysis of candidate genes.

Aldosterone synthase deficiency due to a novel mutation in CYP11B2

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

The clinical significance of aldosterone synthase deficiency: report of a novel mutation in the CYP11B2 gene

BackgroundAldosterone synthase (CYP11B2) deficiency is a rare autosomal recessive disorder, usually presenting with severe salt-wasting in infancy or stress-induced hyperkalaemia and postural hypotension in adulthood. Neonatal screening for congenital adrenal hyperplasia, another cause of salt wasting, using 17-hydroxyprogesterone measurement would fail to detect aldosterone synthase deficiency, a diagnosis which may be missed until the patient presents with salt-wasting crisis. Due to this potential life-threatening risk, comprehensive hormonal investigation followed by genetic confirmation for suspected patients would facilitate clinical management of the patient and assessment of the genetic implication in their offspring.Case presentationWe describe a 33-year old Chinese man who presented in infancy with life-threatening hyponatraemia and failure to thrive, but remained asymptomatic on fludrocortisone since. Chromosomal analysis confirmed a normal male karyotype of 46, XY. Plasma steroid profile showed high plasma renin activity, low aldosterone level, and elevated 18-hydroxycorticosterone, compatible with type 2 aldosterone synthase deficiency. The patient was heterozygous for a novel CYP11B2 mutation: c.977C > A (p.Thr326Lys) in exon 3. He also carried a heterozygous mutation c.523_525delAAG (p.Lys175del) in exon 6, a known pathogenic mutation causing aldosterone synthase deficiency. Sequencing of CYP11B2 in his parents demonstrated that the mother was heterozygous for c.977C > A, and the father was heterozygous for c.523_525delAAG.ConclusionAlthough a rare cause of hyperreninaemic hypoaldosteronism, aldosterone synthase deficiency should be suspected and the diagnosis sought in patients who present with life-threatening salt-wasting in infancy, as it has a good long-term prognosis when adequate fludrocortisone replacement is instituted. To our knowledge, this is the first Chinese patient in which the molecular basis of aldosterone synthase deficiency has been identified.

Two novel mutations of the CYP11B2 gene in a Japanese patient with aldosterone deficiency type 1

Isolated hypoaldosteronism is a rare and occasionally life-threatening cause of salt wasting in infancy. A 2-month-old Japanese boy of unrelated parents was examined for failure to thrive and poor weight gain. Laboratory findings were hyponatremia, hyperkalemia, high plasma renin and low aldosterone levels. Spot urine analysis by gas chromatography-mass spectrometry (GC-MS) showed that urinary excretion of corticosterone metabolites was elevated. Whereas excretion of 18-hydroxycortricosterone metabolites was within the normal range, excretion of aldosterone metabolites was undetectable. The patient was therefore suspected to have aldosterone synthase deficiency type 1. Sequence analysis of CYP11B2, the gene encoding aldosterone synthase (CYP11B2), showed that the patient was a compound heterozygote for c.168G>A, p.W56X in exon 1 and c.1149C>T, p.R384X in exon 7. p.W56X was inherited from his mother and p.R384X was from his father. Since both alleles contain nonsense mutations, a lack of CYP11B2 activity was speculated to cause his condition. To our knowledge, this is the first Japanese patient in which the molecular basis of aldosterone synthase deficiency type 1 has been clarified. This case also indicates that spot urinary steroid analysis is useful for diagnosis.

Déficit en aldostérone-synthase : 4 observations pédiatriques

Neonatal salt-wasting syndromes are rare but potentially serious conditions. Isolated hypoaldosteronism is an autosomal recessive inherited disorder of terminal aldosterone synthesis, leading to selective aldosterone deficiency. Two different biochemical forms of this disease have been described, called aldosterone synthase deficiency or corticosterone methyl oxydase, types I and II. In type I, there is no aldosterone synthase activity and the 18 hydroxycorticosterone (18 OHB) level is low, whereas in type II, a residual activity of aldosterone synthase persists and 18 OHB is overproduced. We report on four patients with isolated hypoaldosteronism. In 2 of them, who were recently diagnosed with aldosterone synthase deficit, we discuss the symptoms and treatment. The 2 other patients are now adults. We discuss the long-term outcome, the quality of adult life, aldosterone synthase deficits, as well as the pathophysiology and molecular analysis.

Homozygosity for a mutation in the CYP11B2 gene in an infant with congenital corticosterone methyl oxidase deficiency type II

Isolated aldosterone synthase deficiency can be the source of life-threatening salt wasting and failure to thrive in infancy. We studied an infant with failure to thrive and persistent hyponatremia despite oral sodium supplementation. Initial analyses revealed highly elevated plasma renin but normal values of plasma aldosterone. The biochemical diagnosis of corticosterone methyl oxidase deficiency type II was established by multisteroid analysis, revealing a pathognomonic pattern with a highly elevated ratio of 18-OH-corticosterone to aldosterone. This reflects an enzymatic defect in the aldosterone synthase that is responsible for the terminal steps in the aldosterone biosynthesis. Molecular genetic analysis supported the diagnosis revealing homozygosity for a pathogenic c.554C>T (p.T185I) variation in exon 3 of the CYP11B2 gene encoding aldosterone synthase. Homozygosity for two other polymorphic variations c.504C>T (p.F168F) and c.518A>G (p.K173R) were identified as well. Treatment with fludrocortisone resulted in catch-up growth. Discontinuation of treatment at the age of 9 years was later possible without any clinical or biochemical deterioration. Isolated deficiency in aldosterone biosynthesis should be considered in neonates and infants with failure to thrive and salt wasting. Normal levels of plasma aldosterone compared with highly elevated levels of plasma renin indicate an impaired aldosterone biosynthesis and suggest the disorder. Recognition of its existence is important as fludrocortisone replacement therapy effectively normalizes sodium balance and growth.