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.

Exogenous steroid-induced hypoadrenalism in a person living with HIV caused by a drug-drug interaction between cobicistat and intrabursal triamcinolone.

We report a diagnosis of exogenous steroid-induced hypoadrenalism in a person living with HIV caused by a drug-drug interaction (DDI) between intrabursal triamcinolone and the pharmacokinetic booster cobicistat. A 53-year-old woman living with HIV, managed with dolutegravir and cobicistat-boosted darunavir, presented to the orthopaedic clinic with worsening hip pain. She was diagnosed with greater trochanteric pain syndrome (GTPS) of the hip and was treated with intrabursal injection of bupivacaine and triamcinolone. Seven days following this injection, she presented with Cushingoid features, an undetectable cortisol and was diagnosed with exogenous steroid-induced hypoadrenalism. Cobicistat is a cytochrome P450 3A inhibitor and in this case inhibited clearance of intrabursal triamcinolone, leading to exogenous glucocorticoid excess and adrenal suppression. This is the first report to describe this predictable DDI with cobicistat following intrabursal glucocorticoid injection. This case highlights the complexities in managing non-HIV-related chronic morbidities in people living with HIV.

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.

Disorders of aldosterone synthesis, secretion, and cellular function.

PURPOSE OF REVIEW: The purpose of this review is to describe the renin-angiotensin-aldosterone system and its regulatory control of sodium, potassium, chloride, hydrogen ion, and water homeostasis through its effects on the expression and activity of distal renal tubular cotransporter proteins and to discuss the gene mutations encoding these structures that disturb the function of this system. RECENT FINDINGS: Primary hypoaldosteronism may be the result of acquired or congenital errors in renal juxtaglomerular function (the source of renin), angiotensin generation or activity, or aldosterone synthesis. Secondary hypoaldosteronism (pseudohypoaldosteronism) occurs as a consequence of mutations in genes encoding the mineralocorticoid receptor (MR), the three subunits of the aldosterone-responsive, amiloride-sensitive nonvoltage-gated sodium channel encoded by SCNN1A, SCNN1B, and SCNN1G, the gene that regulates posttranslational phosphorylation (encoded by WNK4) of the thiazide-sensitive sodium chloride cotransporter encoded by SLC12A3, and those that regulate phosphorylation and ubiquitination of cofactors encoded by WNK1, KLH3, and CUL3 that affect WNK4 function. SUMMARY: Acquired disorders of renal function as well as mutations in many genes may adversely affect aldosterone-mediated mineral homeostasis.

[Four cases of aldosterone synthase deficiency in childhood]. / 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.

Novel CYP11B2 mutation causing aldosterone synthase (P450c11AS) deficiency.

UNLABELLED: Aldosterone synthase (P450c11AS) deficiency is a rare autosomal recessive disorder, presenting with severe salt-losing in early infancy. It is caused by inactivating mutations of the CYP11B2 gene. Here, we describe three unrelated Asian patients who have clinical and hormonal features compatible with aldosterone synthase deficiency and identify their CYP11B2 mutations. Patient 1 was a Thai female infant. Patient 2 was an Indian boy, and patient 3 was a Thai male infant. All subjects presented at the age of 1-2 months with diarrhea, failure to thrive, and severe dehydration. Their plasma electrolytes showed hyponatremia, hyperkalemia, and acidosis. All patients had normal cortisol response and had elevated plasma renin activity with low aldosterone levels. The entire coding regions of the CYP11B2 gene were amplified by polymerase chain reaction and sequenced. Patient 1 was homozygous for a previously described mutation, p.T318M. Patient 2 was homozygous for a novel c.666delC mutation inherited from both parents resulting in p.223F>Sfsx295. No CYP11B2 mutation was detected in patient 3. CONCLUSIONS: We report the first CYP11B2 defects in Southeast Asian families responsible for aldosterone synthase deficiency and identified a novel CYP11B2 mutation. However, the affected gene(s) responsible for primary hypoaldosteronism other than CYP11B2 remain to be determined.

Hyperkalemia after acute metabolic decompensation in two children with vitamin B12-unresponsive methylmalonic acidemia and normal renal function.

The patients affected by vitamin B12-unresponsive methylmalonic acidemia (MMA) on the long run develop chronic renal disease with interstitial nephropathy and progressive renal insufficiency. The mechanism of nephrotoxicity in vitamin B12-unresponsive MMA is not yet known. Chronic hyporeninemic hypoaldosteronism has been found in many cases of methylmalonic acidemia, hyperkalemia and renal tubular acidosis type 4. We report 2 patients affected by B12-unresponsive methylmalonic acidemia diagnosed at the age of 23 months and 5 years, respectively, with normal glomerular filtration and function. They showed hyporeninemic hypoaldosteronism and significant hyperkalemia requiring sodium potassium exchange resin (Kayexalate) therapy after an episode of metabolic decompensation leading to diagnosis of MMA. In both children, hyporeninemic hypoaldosteronism and hyperkalemia disappeared after 6 months of good metabolic control.

Hypertension in a patient with aldosterone deficiency.

OBJECTIVE: To describe a patient with aldosterone synthase deficiency, who presented with failure to thrive, hypovolemic hyponatremia, and the unexpected finding of hypertension. METHODS: We present a case report, review the related literature, and outline a possible mechanism for the concomitant occurrence of high blood pressure and hyponatremia in this patient. RESULTS: A 5-month-old infant with unambiguous female genitalia was admitted to our hospital with failure to thrive and hyponatremia. Her blood pressure was 115/88 mm Hg (>95% for age). The serum sodium concentration was 123 mEq/L (normal for age, >130), and the potassium level was 5.3 mEq/L (normal, 3.5 to 5.3). A direct renin measurement by immunochemiluminescence assay was 11,400 microU/mL (normal, <5), and the aldosterone level was 4 ng/dL (normal, 2 to 70). These findings indicated a diagnosis of aldosterone synthase deficiency. Treatment with fludrocortisone and sodium chloride was begun, but the hypertension worsened. Therapy with an angiotensin-converting enzyme inhibitor was transiently required. CONCLUSION: Angiotensin II, a potent vasoconstrictor, is an intermediate in the renin-angiotensin system. We believe that this protein was the cause of the hypertension in the setting of aldosterone deficiency in our patient.

Isolated adrenocorticotropin deficiency presenting with impaired renin-angiotensin-aldosterone system and suppressed parathyroid hormone-vitamin D axis.

We report here a 47-year-old woman with isolated adrenocorticotropin (ACTH) deficiency (IAD). She presented impaired renin-angiotensin-aldosterone (R-A-A) system and suppressed parathyroid hormone (PTH)-vitamin D system. She showed severe hyponatremia due to secondary adrenocortical insufficiency, which was deteriorated by hypoaldosteronism. She also showed hyperphosphatemia and relative hypercalcemia with suppressed PTH-vitamin D axis. Moreover, she showed hypothyroidism, which was thought to be important to maintain normal Ca levels under secondary hypoadrenalism via decrease in bone resorption by T3. Replacement with glucocorticoid completely normalized PTH-vitamin D axis and R-A-A system. Thus, the present case implicates that severe adrenocortical deficiency due to IAD might affect both R-A-A system and PTH-vitamin D axis. These findings suggest that the ACTH-cortisol axis has an important role in mineral metabolism in vivo.

Hyperkalaemia and selective hypoaldosteronism in myotonic dystrophy.

Myotonic dystrophy (MyD) is a common genetic neuromuscular disorder in which chromosome 19 gives rise to an abnormal expansion of CTG-trinucleotide repeats. MyD is a highly variable multisystem disorder with muscular and nonmuscular abnormalities. Increasingly, endocrine abnormalities, such as gonadal, pancreatic, and adrenal dysfunction are being uncovered. Herein we present three unrelated cases with MyD with abnormally elevated serum potassium; 2 of the 3 cases presented clinically with cardiac dysrhythmias. Hyperkalaemic conditions such as renal failure, cortisol deficiency, pseudohyperkalaemia, and hyperkalaemic periodic paralysis were excluded. Further endocrine evaluation revealed baseline hypoaldosteronism associated with elevated renin activity. Perturbation of the renin-angiotensin-aldosterone system resulted in appropriately enhanced renin activity but with a subnormal aldosterone response, which appeared to be due to adrenal hyporesponsiveness. The treatment of all cases with fludrocortisone was without effect. Whether the apparent mineralocorticoid abnormality in MyD is due to associated hormonal perturbations (i.e. excessive ACTH responsiveness. elevated cytokines, elevated atrial natriuretic hormone, etc.), adrenal atrophy, and/or a manifestation of the underlying kinase dysfunction is uncertain, but merits further evaluation in view of the clinical consequence of hyperkalaemia.

[Hypertension and mineralocorticoids. Usefulness of renin and aldosterone measurements]. / Hipertensión arterial y mineralocorticoides: utilidad de las mediciones de renina y aldosterona.

Recently, some genetic forms of hypertension have been well characterized. These forms can be globally called mineralocorticoid hypertension and are due to different alterations of the renin-angiotensin-aldosterone system (SRAA). Among these, classic primary hyperaldosteronism and its glucocorticoid remediable variety, in which hypertension is secondary to aldosterone production, must be considered. There are also conditions in which mineralocorticoid activity does not depend on aldosterone production. These conditions generate a hyporeninemic hyperaldosteronism, observed in Liddle syndrome, apparent mineralocorticoid hypertension, 11- and 17-hydroxylase deficiency, among others. The detection of these forms of hypertension is only feasible if the renin-angiotensin-aldosterone system is assessed, measuring renin and aldosterone levels. This article reviews these forms of hypertension, their clinical workup and their relevance in the usual hypertensive patients.

Hyper- and hypoaldosteronism.

Aldosterone participates in blood volume and serum potassium homeostasis, which in turn regulate aldosterone secretion by the zona glomerulosa of the adrenal cortex. Autonomous aldosterone hypersecretion leads to hypertension and hypokalemia. Improved screening techniques have led to a re-evaluation of the frequency of primary aldosteronism among adults with hypertension, recognizing that normokalemic cases are more frequent than was previously appreciated. The genetic basis of glucocorticoid remediable aldosteronism has been elucidated and adequately explains most of the pathophysiologic features of this disorder. A new form of familial aldosteronism has been described, familial hyperaldosteronism type II; linkage analysis and direct mutation screening has shown that this disorder is unrelated to mutations in the genes for aldosterone synthase or the angiotensin II receptor. The features of aldosterone hypersecretion may be due to non-aldosterone-mediated mineralocorticoid excess. These include two causes of congenital adrenal hyperplasia (11 beta-hydroxylase deficiency and 17 alpha-hydroxylase deficiency), the syndrome of apparent mineralocorticoid excess (AME) due to 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) deficiency, primary glucocorticoid resistance, Liddle's syndrome due to activating mutations of the renal epithelial sodium channel, and exogenous sources of mineralocorticoid, such as licorice, or drugs, such as carbenoxolone. The features of mineralocorticoid excess are also often seen in Cushing's syndrome. Hypoaldosteronism may lead to hypotension and hyperkalemia. Hypoaldosteronism may be due to inadequate stimulation of aldosterone secretion (hyporeninemic hypoaldosteronism), defects in adrenal synthesis of aldosterone, or resistance to the ion transport effects of aldosterone, such as are seen in pseudohypoaldosteronism type I (PHA I). PHA I is frequently due to mutations involving the amiloride sensitive epithelial sodium channel. Gordon's syndrome (PHA type II) is due to resistance to the kaliuretic but not sodium reabsorptive effects of aldosterone for which the genetic basis is still unknown. This review aims to provide a survey of the clinical disorders of aldosterone excess and deficiency and their clinical management, with a focus on primary aldosteronism and isolated aldosterone deficiency.

Hyporeninemic hypoaldosteronism in patients with nephrotic syndrome.

Five nephrotic patients, who did not present sodium retention when on sodium balance, have been studied. All had membranous nephropathy, were normotensive and renal function was normal in 2 and slightly reduced in 3. The following parameters were measured: 24-hour excretion of aldosterone, the response of plasma renin activity (PRA) and of plasma aldosterone to upright posture, postural changes of the fractional excretion of sodium and lithium, and natriuretic response to spironolactone. The resting values of plasma aldosterone were low in all patients, and after stimulation by upright posture they increased hardly to the low-normal limit only in 1 patient. Resting PRA was normal in all patients and increased slightly, after stimulation. The 24-hour urinary excretion of aldosterone was low in 4 patients and borderline in 1. No natriuretic response to spironolactone was observed in any patients. After upright posture the fractional excretions of sodium and lithium decreased significantly and to the same extent in all patients. Four nephrotic patients with fluctuating, spontaneous episodes of sodium retention and of sodium excretion have been studied as controls. These patients had normal values of urinary aldosterone and of resting PRA and aldosterone. After upright posture the changes of PRA and of aldosterone were clearly evident in 2, and exaggerated in the other 2 patients. In these patients, a significant increase of sodium excretion occurred after treatment with spironolactone. These results suggest that a not negligible number of patients with nephrotic syndrome have hyporeninemic hypoaldosteronism. This diagnosis should be taken into account when investigating the role of aldosterone in sodium retention in nephrotic syndrome.

Genotype-phenotype analysis of a newly discovered family with Liddle's syndrome.

OBJECTIVE: To investigate the clinical, biologic, and molecular abnormalities in a family with Liddle's syndrome and analyze the short- and long-term efficacies of amiloride treatment. PATIENTS: The pedigree consisted of one affected mother and four children, of whom three suffered from early-onset and moderate-to-severe hypertension. METHODS: In addition to the biochemical and hormonal measurements, genetic analysis of the carboxy terminus of the beta subunit of the epithelial sodium channel (beta ENaC) was conducted through single-strand conformation analysis and direct sequencing. The functional properties of the mutation were analyzed using the Xenopus expression system and compared with one mutation affecting the proline-rich sequence of the beta ENaC. RESULTS: Mild hypokalemia and suppressed levels of plasma renin and aldosterone were observed in all affected subjects. Administration of 10 mg/day amiloride for 2 months normalized the blood pressure and plasma potassium levels of all of the affected subjects, whereas their plasma and urinary aldosterone levels remained surprisingly low. A similar pattern was observed after 11 years of follow-up, but a fivefold increase in plasma aldosterone was observed under treatment with 20 mg/day amiloride for 2 weeks. Genetic analysis of the beta ENaC revealed a deletion of 32 nucleotides that had modified the open reading frame and introduced a stop codon at position 582. Expression of this beta 579del32 mutant caused a 3.7 +/- 0.3-fold increase in the amiloride-sensitive sodium current, without modification of the unitary properties of the channel. A similar increase was elicited by one mutation affecting the carboxy terminus of the beta ENaC. CONCLUSIONS: This new mutation leading to Liddle's syndrome highlights the importance of the carboxy terminus of the beta ENaC in the activity of the epithelial sodium channel. Small doses of amiloride are able to control the blood pressure on a long-term basis in this monogenic form of hypertension.