Utility of Genetic Analysis in Rare Tubulopathies Presenting with Bilateral Nephrocalcinosis in Adults - Avoiding Harm with Precision Care: A Case Series

In this article we report a classic Bartter syndrome Type III case who had bilateral nephrocalcinosis We represented this case because of no paper in the literature before nbsp; The patient was five months old boy Gestational age was 35 weeks complicated by admission severe polyhydroarnnios His birth weight was 2700 gr At admission he had severe dehydration growth retardation normotension Laboratory studies revealed hypokalemia metabolic alkalosis hyponatremia hypochloremia polyuria and elevated plasma levels of renin and aldosterone There was bilateral grade I medullary nephrocalcinosis in the abdominal ultrasonography Clinical and laboratory findings improved after fluid replacement potassium supplementation and indornethacin Gene analysis revealed CIC NkB mutation confirming the patient s diagnosis as Bartter s syndrome type III Key words: Bartter syndrome hypokalemia metabolic alkalosis hyperreninism

We report a case of 45-year-old women with Bartter's syndrome and concomitant renal dysfunction. In 1986, the patient demonstrated muscle weakness and serum potassium levels as low as 1.1 mEq/l. She was suspected of having Bartter's syndrome because of hypokalemia, metabolic alkalosis, hyperreninemia, hyperaldosteronism and normotension. Pretibial edema developed in 1989 for which she received 40 to 100 mg/week of furosemide intermittently for the next 5 years. Her serum potassium level ranged from 1.5 to 3.9 mEq/l. In 1991, her serum creatinine level rose to 2.1 mg/dl, then continued to increase gradually. She was admitted to our hospital in 1994 for evaluation of the renal dysfunction. Decreased creatinine clearance (44 ml/min) and a defect in urinary concentrating capacity (Fishberg's test, 370 mOsm/kg.H2O) were detected. Renal biopsy revealed juxtaglomerular cell hyperplasia. These findings resulted in the diagnosis of Bartter's syndrome. The renal biopsy also showed diffuse interstitial fibrosis and marked tubular atrophy. We postulate in this case that long-term hypokalemia due to Bartter's syndrome and the administration of furosemide led to chronic interstitial nephritis and renal dysfunction.

Patient: Male, 28-year-oldFinal Diagnosis: Congenital chloride diarrheaSymptoms: Alkalosis • diarrhea • hypokalemiaMedication: —Clinical Procedure: —Specialty: NephrologyObjective:Rare diseaseBackground:Congenital chloride diarrhea (CCD) is an autosomal recessive disease that is usually diagnosed in early childhood. Mutations in the SLC26A3 gene have been attributed to the primary etiology of disease development. Patients with CCD usually present with electrolyte disturbances, metabolic alkalosis, and chronic diarrhea. Early diagnosis is essential to prevent long-term complications that often require genetic testing. Bartter syndrome is another congenital disorder that has clinical features similar to CCD, which might cause a delay in diagnosis in a few patients.Case Report:We describe the case of a 28-year-old man who was misdiagnosed as having Bartter syndrome when he was 5 months old based on the clinical features of hypokalemia, metabolic alkalosis, and a family history of Bartter syndrome. He had multiple admissions with diarrhea and was diagnosed with ulcerative colitis. Unfortunately, the course was complicated by renal failure, and the patient underwent a kidney transplant. Persistent metabolic alkalosis with diarrhea after transplantation was unusual in Bartter syndrome. Therefore, his primary diagnosis was challenged and suspicion of CCD was raised, which was confirmed by genetic testing.Conclusions:CCD is a rare congenital disorder that requires high clinical suspicion and often a genetic test to confirm diagnosis. Here, we report a patient who was misdiagnosed as having Bartter syndrome until early adulthood owing to several misleading factors. We hope by reporting this case it will raise awareness about CCD in high-prevalence areas and the importance of early diagnosis to prevent serious complications.

Objective To identify and analyze the variants of the KCNJ1 gene in five Chinese patients with Bartter syndrome type 2 (BS2), and to describe their clinical features as well as treatment results. Methods Data and blood samples of five BS2 patients and their relatives confirmed by Qingdao Municipal Hospital from June 2012 to January 2019 were collected. Whole-exome-sequencing (WES) based on the second generation high throughput sequencing was performed to detect variants. The 2015 American College of Medical Genetics and Genomics Standards and Guidelines were applied to analyze the pathogenicity of the variants. The clinical features and laboratory results were retrospectively studied. The response to treatment and follow-up data were reviewed. Results Ten variants including six novel ones of KCNJ1 gene were identified through WES and verified by Sanger dideoxy sequencing. Missense variants accounted for the highest proportion. The common symptoms and signs of five BS2 patients from high to low incidence were polydipsia and polyuria (5/5), one of them (1/5) presented with diabetes insipidus; maternal polyhydramnios and premature delivery (4/5); growth retardation (3/5). Initially, two patients presented with hypochloremic metabolic alkalosis and hypokalemia, whereas the acid-base disturbance was absent in the others. One patient experienced hyperkalemia. In terms of calcium-phosphorus metabolism, one patient had evident parathyroid hormone (PTH) resistance (hypocalcemia, hyperphosphatemia and markedly elevated serum intact PTH levels), three presented with PTH overacting (hypercalcemia, hypophosphatemia and mild elevated serum intact PTH levels), and one showed normal blood calcium and phosphorus concentrations with high-normal serum intact PTH levels. All patients had nephrocalcinosis or hypercalciuria, and one of them complicated with nephrolithiasis. Indomethacin helped to correct the growth retardation, halt polydipsia polyuria, decrease the elevated urinary calcium excretion, and normalize electrolyte disturbance as well as PTH parameters in some patients. Conclusions This investigation identifies ten variants of KCNJ1 gene, including six ones that have not been previously reported, which will enrich the human gene mutation database (HGMD). These patients in our study have atypical BS phenotype, so that careful differentiation from other parathyroid diseases will be required for clinicians. Key words: Bartter syndrome; Genotype; Phenotype; KCNJ1 gene

The incidence of metastatic calcification is influenced by high serum calcium and phosphate concentrations and local physicochemical conditions, such as pH. A high pH accelerates tissue calcification. Patients with milk-alkali syndrome typically present with renal failure, hypercalcemia, and metabolic alkalosis, which are caused by the ingestion of calcium and absorbable alkali. Among patients with impairment of renal function, milk-alkali syndrome is a major cause of hypercalcemia. Long-term use of furosemide will lead to hypokalemia, metabolic alkalosis, and eventually renal failure (i.e., pseudo-Bartter syndrome). Even if the level of calcium ingestion is relatively low, the renal failure caused by long-term furosemide use can readily lead to milk-alkali syndrome. We describe a case of a 45-year-old woman who was admitted with cough and dyspnea and presented with pulmonary and gastric metastatic calcification. She had been taking alfacalcidol and oral alkaline medications such as sodium bicarbonate and calcium carbonate as well as oral furosemide for a long time. The patient was found to have hypercalcemia, chronic renal failure, and metabolic alkalosis, so milk-alkali syndrome was diagnosed. Saline was administered and oral medications were discontinued. Serum creatinine levels subsequently decreased, but pulmonary metastatic calcification was not diminished. In this case, the milk-alkali syndrome that caused the severe metastatic calcification was exacerbated by multiple factors, including oral alkaline medications such as sodium bicarbonate and calcium carbonate. In addition, metabolic alkalosis and renal failure were affected by long-term furosemide use (i.e., pseudo-Bartter syndrome).

Bartter's Syndrome with Type 2 Diabetes Mellitus

Congenital adrenal hyperplasia is an autosomal recessive disease marked by lack of enzymes required to produce specific hormones. About 90-95% of CAH are caused by steroid 21-hydroxylase deficiency and are the result of mutations in the CYP21A2 gene. Bartter syndrome is a rare autosomal recessive disorder characterized by hyperreninemia, metabolic alkalosis, hypokalaemia, and hypochloremia by activation of the RAS. The underlying renal abnormality results in electrolyte and acid-base imbalance abnormalities. We present a rare case of NCCAH coexisting with Bartter syndrome. A 5 years and 7 months old male was diagnosed with NCCAH at 20 days of life presented with fever and cold for one month, as well as recurrent UTIs for two weeks. General physical examination revealed carpopedal spasm, pubic hairs (+) with penile length (8.5 cm). Investigation revealed kaliuresis, hypercalciuria, metabolic alkalosis, hypokalaemia, and hypochloremia. X-ray of the left wrist revealed bone age as 9 years and genetic analysis was recommended. NCCAH with coexisting BS complicated with central precocious puberty was diagnosed. Symptomatic treatment was administered, and long-term steroid replacement advised. Congenital adrenal hyperplasia and Bartter syndrome is difficult to treat, and there is currently no complete cure. Close monitoring and prompt electrolyte replacement with symptomatic treatment are recommended.

A 10-year-old boy was admitted to hospital with a 3 month history of intermittent spasms of the wrists and ankles, and twitching of the eyelids. He also had polyuria, polydipsia, nocturnal enuresis, fatigue and constipation since he was a toddler. Physical examination revealed normal blood pressure, myokymia on the right eyelid and bilateral carpopedal spasms. Laboratory investigation revealed hypocalcemia, hypokalemia, increased plasma renin and aldosterone , hypercalciuria, metabolic alkalosis, and bilateral medullary nephrocalcinosis. Cranial computed tomography was normal. Based on the clinical and laboratory findings he was diagnosed as having Bartter’s syndrome, which is characterized by hypochloremia, hypokalaemia and metabolic alkalosis associated with potassium renal leakage, with normal blood pressure despite increased plasma renin activity. It is well known that tetany is not uncommon in the neonatal form of Bartter’s syndrome and nephrocalcinosis is usually not present in the classic form. Interestingly, our patient had both the clinical manifestations of the neonatal form and of the classic form of Bartter’s syndrome. In conclusion, we would like to emphasize that both the clinical manifestations of neonatal and classic forms of Bartter’s syndrome (as an overlapping syndrome) might be seen in children and that Bartter’s syndrome should also be considered in children with tetany as in our case. (J Pediatr Neurol 2004; 2 (1): 45-47).

The utility of next generation sequencing in the correct diagnosis of congenital hypochloremic hypokalemic metabolic alkalosis

Progressive renal failure in patients with classic Bartter's syndrome (cBS) due to inactivating mutations in CLCNKB gene is extraordinarily rare. We describe a 17-year-old Chinese boy who presented with progressive muscle weakness and renal failure. He was diagnosed as BS of unknown type at the age of 9 months and treated with indomethacin (2 mg/kg/day) and potassium chloride (KCl) supplementation (1.5 mEq/kg/day) for hypokalemia (2.5 mmol/l). At the age of 12 years, serum K+ was 3.0 mmol/l and creatinine reached 2.0 mg/dl. On admission, his blood pressure was normal but volume status was depleted. Urinalysis was essentially normal. Biochemical studies showed hypokalemia (K+ 2.4 mmol/l) with a high transtubular K+ gradient (TTKG) 9.6, metabolic alkalosis (HCO3- 28.4 mmol/l), normomagnesemia (2.0 mg/dl), severe renal failure (BUN 94 mg/dl, Cr 6.3 mg/dl), and hypocalciuria (urine calcium/creatinine ratio 0.02 mg/mg). Abdominal sonography revealed bilateral small size kidneys without nephrocalcinosis or renal stones. After the withdrawal of indomethacin with regular KCl and adequate fluid supplementation for 1 year, serum creatinine and K+ levels have been maintained at 4.0 mg/dl and 3.3 mmol/l, respectively. Direct sequencing of NKCC2, ROMK, ClC-Kb, and NCCT in this patient disclosed a novel homozygous missense mutation (GGG to GAG, G470E) in CLCNKB. This G470E mutation was not identified in 100 healthy Chinese subjects. Long-term therapy of non-steroidal anti-inflammatory drugs (NSAIDs), prolonged hypokalemia, chronic volume depletion, and underlying genetic variety may contribute to the deterioration of his renal function. The cautious use of NSAIDs, aggressive correction of hypokalemia, and avoidance of severe volume depletion may prevent the irreversible renal damage in patients with BS due to a Cl- channel defect.

Bartter syndrome, a group of disorders that encompasses multiple genetic defects with similar clinical presentation, has been divided into six different genotypes, according to different genetic defects, and into three main clinical variants (or phenotypes). Classic laboratory findings in all variants include hypochloremia, hypokalemia, and metabolic alkalosis with excessive excretion of chloride and potassium. Classic Bartter syndrome, neonatal Bartter syndrome, and Gitelman syndrome are the three main clinical variants. Classic Bartter syndrome and neonatal Bartter syndrome have defects in genes that affect transport channels in the ascending loop of Henle, where as in Gitleman syndrome the defect occurs in the transport channels of the distal convoluted tubule. Classic Bartter syndrome and neonatal Bartter syndrome have similar presenting symptoms, potential outcomes, and treatment, but different ages at presentation. Gitelman syndrome, a more benign condition than the other clinical variants, has the classic hallmark finding of hypomagnesemia and low to normal excretion of calcium. This differentiates it from the classic and neonatal variants of the disease. With early diagnosis and proper treatment, Bartter syndrome has a good prognosis. But failure to identify it can lead to tubulointerstitial nephritis and renal failure. We present a case of a 6-month-old boy with Bartter syndrome who presented with poor weight gain and an abdominal mass.

The counter-regulatory arm of the renin-angiotensin system and COVID-19: insights from Gitelman's and Bartter's syndromes.

Bartter syndrome (BS) is a rare congenital salt-losing renal tubular transport disorder, characterized by salt wasting, polyuria, biochemical abnormalities, and acid-base homeostasis imbalance. The syndrome has five different genetic forms, and novel mutations of CLCNKB gene lead to type 3 BS also known as classic BS. In this case, we report clinical and molecular findings from a newborn baby with BS. A 10-day-old male infant born at 37 weeks of gestation by cesarean section following a pregnancy complicated with polyhydramnios, and fetal distress to a 30-year-old gravida 3, para 3 mother, with a 2500 g birth weight was brought to the pediatric emergency department due to weight loss and jaundice. The neonate was referred to the neonatal intensive care unit (NICU) with a preliminary diagnosis of hyponatremic dehydration (Na: 122 mmol/L, 10% dehydration) and hypokalemic hypochloremic metabolic alkalosis (K: 2.13 mmol/L, Cl: 63 mmol/L, pH: 7.62, pCO2 : 39 mmHg, HCO3 : 40.8 mmol/L, BE: 16.9 mmol/L), and hypocalcemia (ionized Ca: 0.72 mmol/L). On arrival to the NICU, symptomatic focal seizures, and polyuria complicated his course. Spot urine biochemistry revealed a renal salt wasting and hypercalciuria: Creatine 11.4 mg/dL Na: 51 mmol/L (54-150), K: 26 mmol/L (20-80), Cl: 164 mmol/L, fractional excretion of sodium (FENa): 3% (0.9-1.6), fractional excretion of chloride (FECl): 17% (<0.5%) and Ca/Cr: 0.33 (<0.2). Biochemical abnormalities disappeared through intravenous fluid and electrolyte therapy, but he could not achieve adequate weight gain, and polyuric urine output (6.5 cc/kg/h), and metabolic alkalosis continued as the enteral feedings advance. Patient's serum renin: 184 pg/mL (5-27 pg/mL) and aldosterone: 1670 pg/mL (1-180 ng/dL) were elevated. Polyuria, renal salt wasting, electrolyte and acid-base disturbances, and hyperreninemic hyperaldosteronism established the diagnosis as Bartter syndrome. An oral indomethacin (1 mg/kg/day) treatment, on the 8th day. ensured the weight gain, and normalized daily urine output. He achieved the goal of birth weight on the 30th day and he was 3520 g weight at discharge on day 42. The genetic tests of the patient as KCNJ1 SLC12A1 gene sequence analysis revealed a novel homozygous mutation in the 14th exon of the CLCNKB gene, the c.1334_1338del CTTTT (p. Ser445fs*4) variant was identified. The diagnosis of BS should be considered in the presence of a medical history of severe polyhydramnios of fetal origin. Postnatally, polyuria, signs of dehydration, renal salt wasting, and hypokalemic-metabolic alkalosis should prompt the clinician to request genetic testing for BS in the neonatal period. This case is presented to emphasize that early diagnosis of BS should be considered in newborns presenting with electrolyte abnormalities and metabolic alkalosis accompanying dehydration and favorable growth results can be achieved by starting indomethacin treatment in the early neonatal period. The clinical exome sequencing illustrated a novel missense variant in the CLCNKB gene leading to the molecular diagnosis of BS type 3.

Bartter syndrome is a genetic disorder with hypokalemic metabolic alkalosis and is classified into five types. Type IV Bartter syndrome is a type of neonatal Bartter syndrome with sensorineural deafness and has been recently shown to be caused by mutations in the BSND gene. Owing to the rarity of this disease, only a limited number of mutations have been reported. We analyzed the BSND gene in a patient with type IV Bartter syndrome. The patient was delivered at 37 weeks, with normal body weight, and his neonatal course was uneventful. He was examined for developmental delay and polyuria at age 1 year 8 months and was found to have hypokalemia, metabolic alkalosis, hyperreninemic hyperaldosteronism, and sensorineural deafness. He developed end-stage renal failure at age 15 years, and renal transplantation was performed. We identified compound heterozygous mutations (Q32X and G47R) in the BSND gene. Each mutation was inherited from the parents. The Q32X mutation is a novel mutation and the first nonsense mutation identified in this gene. The mild perinatal clinical features of the patient were similar to those of a patient reported with a homozygous G47R mutation. However, the severity of renal failure suggested that factors other than this gene might affect the manifestation of renal abnormalities.

Objective To analyze the mutations of causal genes in sixteen Chinese patients with suspicious Bartter syndrome, and follow up their treatment results. Methods Mutations were identified by the next generation sequencing and the multiplex ligation-dependent probe amplification (MLPA). Clinical and biochemical features at the first presentation as well as follow-up results were reviewed. Results 15 different CLCNKB gene mutations were identified in sixteen patients with BS, including 11 novel ones. A novel missense mutation and a novel small deletion were found from SLC12A1 gene. A novel gross deletion was found in CLCNKA gene. A recurrent missense mutation was identified from BSND gene. The whole gene deletion mutation of CLCNKB gene was the most frequent mutation (32%), and the rate of gross deletion was up to 50 percent in this group of Chinese patients. The most common clinical manifestations were development retardation (15/16), polydipsia and polyuria (15/16). All of the patients were detected with hypokalemia, hypochloremia and metabolic alkalosis. Indomethacin treatment had significant improvement to the stature and weight restoration. Conclusion The present study has found 19 mutations, including 14 novel ones, which enriches the human gene mutation database (HGMD) and provides valuable references to the genetic counseling and diagnosis of Chinese population. Key words: Bartter syndrome; Mutation; CLCNKB gene; SLC12A1 gene; BSND gene; Genotype and phenotype