Clinical and Genetic Characteristics of Patients with Corticosterone Methyloxidase Deficiency Type 2: Novel Mutations in CYP11B2

Corticosterone methyloxidase deficiency type 2 is an autosomal recessive disorder presenting with salt loss and failure to thrive in early childhood and is caused by inactivating mutations of the CYP11B2 gene. Herein, we describe four Turkish patients from two families who had clinical and hormonal features compatible with corticosterone methyloxidase deficiency and all had inherited novel CYP11B2 variants. All of the patients presented with vomiting, failure to thrive and severe dehydration, except one patient with only failure to thrive. Biochemical studies showed hyponatremia, hyperkalemia and acidosis. All patients had normal cortisol response to adrenocorticotropic hormone stimulation test and had elevated plasma renin activity with low aldosterone levels. Three patients from the same family were found to harbor a novel homozygous variant c.1175T>C (p.Leu392Pro) and a known homozygous variant c.788T>A (p.Ile263Asn) in the CYP11B2 gene. The fourth patient had a novel homozygous variant c.666_667delCT (p.Phe223ProfsTer35) in the CYP11B2 gene which caused a frame shift, forming a stop codon. Corticosterone methyloxidase deficiency should be considered as a differential diagnosis in patients presenting with hyponatremia, hyperkalemia and growth retardation, and it should not be forgotten that this condition is life-threatening if untreated. Genetic analyses are helpful in diagnosis of the patients and their relatives. Family screening is important for an early diagnosis and treatment. In our cases, previously unreported novel variants were identified which are likely to be associated with the disease.

Hyperkalemia in type 4 renal tubular acidosis associated with systemic lupus erythematosus.

Renal tubular acidosis (RTA) is a normal anion gap metabolic acidosis that manifests with insufficiency of hydrogen ion excretion or bicarbonate (HCO3) reuptake as a result of renal tubular dysfunction independent of glomerular filtration rate. Hypokalemic RTA subtypes co-existing with autoimmune diseases particularly appear in Sjogren's syndrome, but rarely in systemic lupus erythematosus (SLE). Type 4 RTA associated with hyperkalemia is very rare during the course of SLE and hence has been scarcely reported in the literature. Here, we report a 42-year-old patient for whom regular follow-up was ongoing due to class IV lupus nephritis when she developed hyperkalemia. The patient had normal anion gap hyperkalemic metabolic acidosis and her urine pH was 5.5. Type 4 RTA was considered and, therefore, tests for renin and aldosterone levels were requested, which revealed that renin was suppressed and aldosterone was decreased. Upon diagnosis of SLE-associated type 4 RTA, short-term oral HCO3 and fludrocortisone were initiated. Potassium (K) and HCO3 levels improved at day 15 of therapy. In this review, we analyzed our case along with five other reports (a total of seven cases) of SLE-associated type 4 RTA we identified through a literature search. We wanted to highlight RTA for differential diagnosis of hyperkalemia emerging during SLE/lupus nephritis and we also discussed possible underlying mechanisms.

Alterations of adrenal steroidomic profiles in preterm infants at birth.

OBJECTIVE: Preterm infants have relative adrenal and kidney immaturity. Recently, we linked their urine sodium loss to a hypoaldosteronism at variance with an appropriate stimulation of the renin-angiotensin system. To investigate this defective aldosterone secretion, we analyse the biosynthesis pathways of adrenal steroids in neonates according to gestational age (GA). DESIGN: Multicentre study (Premaldo) including 152 neonates classified into three groups: group 1 (very preterm (VPT)): <33 gestational weeks (GW); group 2 (preterm (PT)): 33-36 GW and group 3 (term (T)): ≥GW. METHOD: Steroidomic profiles of mineralocorticoids, glucocorticoids and adrenal androgens were established from umbilical cord at birth (n=152) and peripheral blood at day 3 (n=70) using a recently developed liquid chromatography mass spectrometry method (LC-MS/MS). The enzymatic activity of each biosynthesis step was estimated by the product-to-substrate ratio. RESULTS: At birth, VPT infants exhibit a global defect in adrenal steroid synthesis pathways leading to lower levels of aldosterone, cortisol and androstenedione than in term infants. This defect was strongly related to GA. On day 3, steroid precursors (progesterone, 11-deoxycorticosterone (DOC), 17-hydroxyprogesterone(17-OH-P) and 11-deoxycortisol (S)) were higher in VPT and negatively correlated with GA. Despite of precursors' accumulation, aldosterone and cortisol were similar in the three groups. At birth and day 3, a low cortisol/11-deoxycortisol ratio was found in preterm infants, suggesting an 11-beta-hydroxylase activity (CYP11B1) deficiency. CONCLUSIONS: At birth, VPT infants exhibit a global deficit in mineralocorticoids, glucocorticoids and adrenal androgens that attenuates on day 3 of life. Steroid profiling using LC-MS/MS provides evidence for a partial defect in 11-hydroxylase along with prematurity.

Mechanisms of renal control of potassium homeostasis in complete aldosterone deficiency.

Aldosterone-independent mechanisms may contribute to K(+) homeostasis. We studied aldosterone synthase knockout (AS(-/-)) mice to define renal control mechanisms of K(+) homeostasis in complete aldosterone deficiency. AS(-/-) mice were normokalemic and tolerated a physiologic dietary K(+) load (2% K(+), 2 days) without signs of illness, except some degree of polyuria. With supraphysiologic K(+) intake (5% K(+)), AS(-/-) mice decompensated and became hyperkalemic. High-K(+) diets induced upregulation of the renal outer medullary K(+) channel in AS(-/-) mice, whereas upregulation of the epithelial sodium channel (ENaC) sufficient to increase the electrochemical driving force for K(+) excretion was detected only with a 2% K(+) diet. Phosphorylation of the thiazide-sensitive NaCl cotransporter was consistently lower in AS(-/-) mice than in AS(+/+) mice and was downregulated in mice of both genotypes in response to increased K(+) intake. Inhibition of the angiotensin II type 1 receptor reduced renal creatinine clearance and apical ENaC localization, and caused severe hyperkalemia in AS(-/-) mice. In contrast with the kidney, the distal colon of AS(-/-) mice did not respond to dietary K(+) loading, as indicated by Ussing-type chamber experiments. Thus, renal adaptation to a physiologic, but not supraphysiologic, K(+) load can be achieved in aldosterone deficiency by aldosterone-independent activation of the renal outer medullary K(+) channel and ENaC, to which angiotensin II may contribute. Enhanced urinary flow and reduced activity of the thiazide-sensitive NaCl cotransporter may support renal adaptation by activation of flow-dependent K(+) secretion and increased intratubular availability of Na(+) that can be reabsorbed in exchange for K(+) secreted.

Pathophysiology, diagnosis, and treatment of mineralocorticoid disorders.

The renin-angiotensin-aldosterone system (RAAS) is a major regulator of blood pressure control, fluid, and electrolyte balance in humans. Chronic activation of mineralocorticoid production leads to dysregulation of the cardiovascular system and to hypertension. The key mineralocorticoid is aldosterone. Hyperaldosteronism causes sodium and fluid retention in the kidney. Combined with the actions of angiotensin II, chronic elevation in aldosterone leads to detrimental effects in the vasculature, heart, and brain. The adverse effects of excess aldosterone are heavily dependent on increased dietary salt intake as has been demonstrated in animal models and in humans. Hypertension develops due to complex genetic influences combined with environmental factors. In the last two decades, primary aldosteronism has been found to occur in 5% to 13% of subjects with hypertension. In addition, patients with hyperaldosteronism have more end organ manifestations such as left ventricular hypertrophy and have significant cardiovascular complications including higher rates of heart failure and atrial fibrillation compared to similarly matched patients with essential hypertension. The pathophysiology, diagnosis, and treatment of primary aldosteronism will be extensively reviewed. There are many pitfalls in the diagnosis and confirmation of the disorder that will be discussed. Other rare forms of hyper- and hypo-aldosteronism and unusual disorders of hypertension will also be reviewed in this article.

A case of primary selective hypoaldosteronism carrying three mutations in the aldosterone synthase (Cyp11b2) gene.

An infant with a clinical phenotype of early onset hypoaldosteronism has been screened for mutation analysis of the Cyp11b2 gene encoding aldosterone synthase enzyme. We have described a novel nonsense mutation in exon 3 (c.508C>T) that gave rise to a shorter protein (Q170X) and two known concurrent missense mutations (c.594A>C in exon 3 and c.1157T>C in exon 7) that led to substitution of glutamic acid for aspartic acid at amino acid position 198 (E198D) and of valine for alanine at amino acid position 386 (V386A). The father, who carried E198D plus V386A mutations, showed a fractional sodium excretion of 1.25% that was unmodified by dietary salt restriction, suggesting a mild haploinsufficiency. We examined by in silico analysis the effect of the mutations on the secondary and tertiary structures of aldosterone synthase to explain the inefficient enzymatic activity. The Q170X mutation produced a truncated protein, which was consequently associated with a loss of catalytic activity. As predicted by JPred web system and Dock 6.3 software, the concurrent expression of E198D and V386A mutations induced a significant secondary structure rearrangement and a shift of the heme group and the 18-hydroxycorticosterone substrate from their optimal placement.

Apparent mineralocorticoid excess syndrome: report of one family with three affected children.

The syndrome of apparent mineralocorticoid excess (AME) is an autosomal recessive disorder characterized by hypertension, hypokalemia, low renin, and hypoaldosteronism. It is caused by deficiency of 11ß-hydroxysteroid dehydrogenase, which results in a defect of the peripheral metabolism of cortisol to cortisone. As a consequence, the serum cortisol half-life (T½) is prolonged, ACTH is suppressed, and serum cortisol concentration is normal. The hormonal diagnosis of the disorder is made by the increased ratio of urine-free cortisol to cortisone. In patients with AME, this ratio is 5-18, while in normal individuals it is <0.5. These studies suggest that an abnormality in cortisol action or metabolism results in cortisol behaving as a potent mineralocorticoid and causing the syndrome of AME. We report three siblings - two female and one male - with the syndrome of apparent mineralocorticoid excess who presented with hypertension, hypokalemia, low renin, and low aldosterone levels. The finding of abnormally high ratios of 24-h urine-free cortisol to cortisone in our three patients (case 1, 8.4; case 2, 25; and case 3, 7.5) confirmed the diagnosis of apparent mineralocorticoid excess syndrome in these children. They were treated with oral potassium supplements. The addition of spironolactone resulted in a decrease in blood pressure, rise in serum potassium and a gradual increase in plasma renin activity in all three. In this study, the genetic testing of those three siblings with the typical clinical features of AME has detected missense mutation c.662C>T (p.Arg208Cys) in exon 3 of the HSD11B2 gene in the homozygous state.

[Drug-induced exacerbation of hypoaldosteronism in autoimmune polyglandular syndrome type 2]. / Polekowe nasilenie hipoaldosteronizmu w autoimmunologicznym zespole wielogruczolowym typu 2.

Hypoaldosteronism is a clinical condition resulting from inadequate stimulation of aIdosterone secretion (hyporeninemic hypoaIdosteronism), defects in adrenal synthesis of aldosterone (hyperreninemic hypoaldosteronism), or resistance to the peripheral action of this hormone (pseudohypoaldosteronism). The disease is characterized by a wide spectrum of clinical manifestations, ranging from asymptomatic hyperkalemia to life-threatening volume depletion, and, if unrecognized and untreated, it increases morbidity and mortality rates. In this paper, we report a case of a woman diagnosed with autoimmune polyglandular syndrome type 2. As a consequence of adrenal cortex destruction, the patient developed subclinical hypoaldosteronism which was effectively treated with small doses of fludrocortisone. Two and fours years later, she required ibuprofen and atenolol treatment and each of these treatments was accompanied by a transient deterioration in mineralocorticoid activity which resolved after drug withdrawal. This case shows for the first time that drugs reducing plasma renin activity may unmask subclinical hypoaldosteronism in subjects with autoimmune polyglandular syndromes, and that they should be avoided in patients with even small disturbances in the hormonal function of the zona glomerulosa.

Clinical and molecular characterization of a family with a dominant renin gene mutation and response to treatment with fludrocortisone.

BACKGROUND: A family was identified with autosomal dominant inheritance of anemia, polyuria, hyperuricemia, and chronic kidney disease. Mutational analysis revealed a novel heterozygous mutation c.58T > C resulting in the amino acid substitution of cysteine for arginine in the preprorenin signal sequence (p.cys20Arg) occurring in all affected members. METHODS: Effects of the identified mutation were characterized using in vitro and in vivo studies. Affected individuals were clinically characterized before and after administration of fludrocortisone. RESULTS: The mutation affects endoplasmic reticulum co-translational translocation and posttranslational processing, resulting in massive accumulation of non-glycosylated preprorenin in the cytoplasm. This affects expression of intra-renal RAS components and leads to ultrastructural damage of the kidney. Affected individuals suffered from anemia, hyperuricemia, decreased urinary concentrating ability, and progressive chronic kidney disease. Treatment with fludrocortisone in an affected 10-year-old child resulted in an increase in blood pressure and estimated glomerular filtration rate. CONCLUSIONS: A novel REN gene mutation resulted in an alteration in the amino acid sequence of the renin signal sequence and caused childhood anemia, polyuria, and kidney disease. Treatment with fludrocortisone improved renal function in an affected child. Nephrologists should consider REN mutational analysis in families with autosomal dominant inheritance of chronic kidney disease, especially if they suffer from anemia, hyperuricemia, and polyuria in childhood.

Hyperreninemic hypoaldosteronism syndrome, plasma concentrations of interleukin-6 and outcome in critically ill patients with liver cirrhosis.

OBJECTIVE: To investigate the relation between the adrenal production of gluco- and mineralocorticoids, the inflammatory status and the outcome in critically ill patients with liver cirrhosis. DESIGN: Prospective descriptive study. SETTING: Medical intensive care unit (ICU) in a university hospital. PATIENTS: Fifty consecutive patients with liver cirrhosis. INTERVENTIONS: A corticotropin stimulation test within 12h following ICU admission. Plasma cortisol concentration was measured before and after the test. Renin and aldosterone concentrations, as well as interleukin-6 (IL-6) level to assess the pro-inflammatory status, were measured only before the test. Impaired adrenal function was defined as cortisol response to the test less than 9microg/dl. Hyperreninemic hypoaldosteronism syndrome was defined as basal renin over aldosterone ratio (RRA) higher than 2. MEASUREMENTS AND RESULTS: Forty-one (82%) patients had impaired adrenal function, and 26 patients (52%) presented with RRA > 2. Patients with RRA > 2 exhibited greater disease severity and organ dysfunction scores at baseline, higher levels of serum renin and IL-6, and a greater ICU mortality rate, but risk-adjusted mortality rates were not different between the two groups. Renin and IL-6 plasma concentrations were positively correlated. Finally, in a Cox regression analysis, independent predictors of 30-day mortality were hyperreninemic hypoaldosteronism syndrome, IL-6 higher than 400pg/ml and severe renal failure. CONCLUSIONS: Adrenal dysfunction was common in critically ill cirrhotic patients. Hyperreninemic hypoaldosteronism syndrome was related to a greater pro-inflammatory status and degree of acute organ failure, and was independently associated with a worse prognosis.

Aldosterone synthase deficiency and related disorders.

Aldosterone's main actions are to regulate intravascular volume and serum electrolytes by controlling sodium absorbtion and potassium excretion in the distal nephron. Inherited defects in aldosterone biosynthesis thus cause hypovolemia, hyponatremia and hyperkalemia. Defective aldosterone biosynthesis may be caused by congenital adrenal hyperplasia due to 21-hydroxylase (CYP21) deficiency, in which case cortisol biosynthesis is also affected, or as an isolated defect termed aldosterone synthase (corticosterone methyloxidase, CYP11B2) deficiency. Many mutations have been documented in each of these genes; in general enzymatic activity must be reduced to <1% of normal for aldosterone biosynthesis to be impaired. An additional form of familial hyperreninemic hypoaldosteronism has been described that is not due to mutations in CYP11B2, but its etiology remains to be elucidated.

Selective hypoaldosteronism due to combined defects of the conversion from inactive renin to active renin and the aldosterone biosynthesis from corticosterone.

A 24-year-old Japanese woman with IgA nephropathy exhibited a decreased serum aldosterone level with normal plasma renin activity after toxemia of pregnancy. Our studies revealed selective hypoaldosteronism with normal adrenoglucocorticoid functions. Levels of serum corticosterone and deoxycorticosterone were normal. Resting plasma renin activity was normal, and plasma levels of total and inactive renin were increased. Rapid ACTH administration failed to stimulate any secretion of aldosterone, whereas it adequately increased serum cortisol, deoxycorticosterone, and corticosterone concentrations. Responses of both plasma renin activity and serum aldosterone level to the furosemide-posture challenge were blunted. Angiotensin II also failed to stimulate any secretion of aldosterone despite a progressive rise in blood pressure and an appropriate increase in serum corticosterone. These results suggest that combined defects of the conversion from inactive renin to active renin and aldosterone biosynthesis are the causes of selective hypoaldosteronism in our patient.

[Histochemical characteristics of aldosteromas and adrenal tissue of patients with primary hyperaldosteronism]. / Gistokhimicheskaia kharakteristika al'dosterom i adrenalovoi tkani bol'nykh s pervichnym giperal'dosteronizmom.

The authors analyze the data of histochemical examinations of 30 patients with tumorous and nontumorous forms of low-renin hyperaldosteronism, as well as the findings of clinical and hormonal examinations of these patients. The activities of enzymes involved in steroidogenesis (3-beta OSD, NAD and NADP tetrazolium reductases, G-6-PD) were measured, as were levels and distribution patterns of lipids involved in steroidogenesis (free and bound cholesterol, etc.). A high functional activity of aldosteromas of any structure was proved, and a trend to increase of steroidogenic activity of malignant aldosteromas demonstrated. Atrophic changes in the cortex adjacent to aldosteroma were found to involve no reduction of adrenal tissue functional activity. In contrast to this, hyperplastic changes in the cortex adjacent to adenoma were characterized by a lower level of functional activity as against adrenal tissue activity in nontumorous hyperaldosteronism. The authors come to a conclusion that adrenocortical elements hyperplasia associated with some aldosteromas does not participate in aldosterone hyperproduction whereas hyperaldosteronism in nontumorous variants is caused by cortical cell hyperplasia and hormone hyperproduction.