Distal RTA Research Articles

Alteration of bone microarchitecture in hereditary distal RTA patients with SLC4A1 gene mutation: assessed by HR-pQCT.

Hereditary distal renal tubular acidosis caused by SLC4A1 gene mutation (SLC4A1-dRTA) is a rare hereditary form of renal tubular acidosis. Rickets or osteomalacia is a common complication of SLC4A1-dRTA, and seriously affects patients' daily life. However, studies on the bone microstructure in SLC4A1-dRTA are limited. This work aimed to evaluate the bone microstructure of SLC4A1-dRTA patients, compared to age- and sex-matched healthy controls and X-linked hypophosphatemic rickets (XLH) patients. This was a retrospective study on eleven SLC4A1-dRTA patients. Clinical manifestations, biochemical and radiographical examinations were characterized. Bone microstructure was examined in seven SLC4A1-dRTA patients, seven healthy controls and twenty-one XLH patients using high-resolution peripheral quantitative computed tomography (HR-pQCT). Skeletal symptoms, including fracture, bone pain, and lower limb deformity, were presented in 72.7% of SLC4A1-dRTA patients. Short stature was presented in 63.6% of the patients. SLC4A1-dRTA patients had significantly lower volumetric BMD in the distal tibia, and more severe deteriorated trabecular bone in the distal radius and tibia than healthy controls. SLC4A1-dRTA patients had significantly more severe deteriorated trabecular bone in the distal radius and distal tibia compared to XLH patients. With long-term alkaline therapy, SLC4A1-dRTA patients had alleviation in bone pain, increase in height. Skeletal lesions were common clinical manifestations in SLC4A1-dRTA patients. Compared with XLH, another common type of rickets, SLC4A1-dRTA patients had more severe trabecular bone microstructure damage, further supporting the necessity of early diagnosis and timely treatment of the disease.

Renal tubular acidosis without interstitial nephritis in Sjögren’s syndrome: a case report and review of the literature

BackgroundRenal tubular acidosis is the principal clinical feature associated with tubulointerstitial nephritis in patients with primary Sjögren’s syndrome. Renal tubular dysfunction due to interstitial nephritis has been considered the underlying pathophysiology connecting renal tubular acidosis and primary Sjögren’s syndrome. However, the detailed mechanisms underlying the pathophysiology of renal tubular acidosis in primary Sjögren’s syndrome is not fully understood.Case presentationA 30-year-old woman was admitted with complaints of weakness in the extremities. The patient was hospitalized thirteen years earlier for similar issues and was diagnosed with hypokalemic paralysis due to distal renal tubular acidosis with primary Sjögren’s syndrome. This diagnosis was based on a positive Schirmer's test. Besides, anti-Sjögren’s syndrome-related antigen A was also detected. Laboratory tests indicated distal RTA; however, a renal biopsy showed no obvious interstitial nephritis. Laboratory tests conducted during the second admission indicated distal renal tubular acidosis. Therefore, a renal biopsy was performed again, which revealed interstitial nephritis. Histological analysis of acid–base transporters revealed the absence of vacuolar type H+-ATPases in the collecting duct. The vacuolar type H+-ATPase was also absent in the past renal biopsy, suggesting that the alteration in acid–base transporters is independent of interstitial nephritis.ConclusionsThis case study demonstrates that vacuolar-type H+-ATPases are associated with distal renal tubular acidosis, and distal renal tubular acidosis precedes interstitial nephritis in patients with primary Sjögren’s syndrome.

A Curious Case of Cocaine-Induced Hypokalemic Periodic Paralysis Mimicking Guillain-Barre Syndrome (P10-5.003)

<h3>Objective:</h3> To describe a rare cause of progressive ascending paralysis resembling Guillain-Barre Syndrome (GBS). <h3>Background:</h3> Cocaine inhibits the reuptake of monoamines at the synaptic cleft to prolong sympathetic output. This adrenergic hyperresponsiveness mimics thyrotoxicosis as it replicates sodium/potassium ATPase hyperactivity, causing a cellular influx of potassium (hypokalemia), hyperpolarization, and sodium channel inactivation that presents as sudden, painless muscle weakness and paralysis. <h3>Design/Methods:</h3> Consent obtained from patient. <h3>Results:</h3> A 30-year-old female with no past medical history was evaluated in the ED for acute lower extremity weakness that ascended to the upper extremities within &lt; 12 hours. Labs were significant for hypokalemia at 1.6, elevated inflammatory markers, elevated Free T4 at 2.58, and low TSH at &lt; 0.015. Urine drug screen was positive for cannabis and cocaine. Serum toxicology was negative. MRI of the T-spine and L-spine were unremarkable. Lumbar puncture was unremarkable. Cranial nerves were intact. Strength was 1/5 throughout, including at the neck. Flaccid tone. Lower extremity reflexes were 2+. Negative Babinski. Positive Hoffman bilaterally. Preserved sensation. The patient was admitted to the ICU, intubated for impending respiratory distress, and treated with IVIg. MRI of the C-spine was unremarkable. Further labs demonstrated elevated Free T3 at 7.13 and positive anti-TPO antibodies, significant for Grave’s disease. Urine labs were substantial for distal RTA. Anti-SSA and SSB antibodies were positive, indicating likely Sjogren’s syndrome (SS). Ganglioside panel was negative. Potassium was aggressively repleted. By day 1, the patient was moving all four extremities, and IVIg was discontinued. By day 2, she was successfully extubated. She was ambulating without difficulty on discharge. <h3>Conclusions:</h3> Secondary hypokalemic periodic paralysis may mimic Guillain Barre syndrome (GBS), a life-threatening demyelinating neuropathy that presents as rapidly progressive, symmetric, ascending paralysis or paresthesia with loss of reflexes. In our case, cocaine was the most plausible trigger for hypokalemia. <b>Disclosure:</b> Dr. Baumann has nothing to disclose. Dr. Rizvi has nothing to disclose. Ms. Alayon has nothing to disclose. Mr. Kendall has nothing to disclose. Dr. Shaffer has nothing to disclose. Dr. Mouhanna has nothing to disclose. Dr. Kenniff has nothing to disclose.

RESPIRATORY FAILURE ASSOCIATED WITH DISTAL RENAL TUBULAR ACIDOSIS IN AN OLDER ADULT WITH SOUTHEAST ASIAN OVALOCYTOSIS AND CONCOMITANT THYROTOXIC ATRIAL FIBRILLATION

Distal renal tubular acidosis (dRTA) is characterized by hyperchloremic hypokalemic metabolic acidosis, nephrocalcinosis and metabolic bone disease. It has been associated with Southeast Asian Ovalocytosis (SAO), particularly in malaria endemic region. We present a case of an older adult with dRTA who presented with respiratory failure as a result of hyperchloremic normal anion gap metabolic acidosis, in association with nephrocalcinosis and SAO, however, without hypokalaemia due to concurrent acute kidney injury. Oxygen therapy was able to be weaned off after treatment with alkali supplementation. Distal RTA may be associated with SAO, and early recognition and treatment of dRTA is paramount in preventing complications such as chronic kidney disease, metabolic bone disease and life-threatening respiratory arrest.

Pattern of hereditary renal tubular disorders in Egyptian children.

Hereditary renal tubular disorders (HRTD) represent a group of genetic diseases characterized by disturbances in fluid, electrolyte, and acid-base homeostasis. There is a paucity of studies on pediatric HRTD in Egypt. In this study, we aimed to study the pattern, characteristics, and growth outcome of HRTD at an Egyptian medical center. This study included children from one month to < 18-years of age with HRTD who were diagnosed and followed up at the Pediatric Nephrology Unit of Sohag University Hospital from January 2015 to December 2021. Data on patients` demographics, clinical features, growth profiles, and laboratory characteristics were collected. Fifty-eight children (57% males; 72% parental consanguinity; 60% positive family history) were diagnosed with seven HRTD types. The most commonly encountered disorders were distal renal tubular acidosis (distal renal tubular acidosis [RTA] 27 cases, 46.6%) and Bartter syndrome (16 cases 27.6%). Other identified disorders were Fanconi syndrome (6 cases with cystinosis), isolated proximal RTA (4 cases), nephrogenic diabetes insipidus (3 cases), and one case for each RTA type IV and Gitelman syndrome. The median age at diagnosis was 17 months with a variable diagnostic delay. The most common presenting features were failure to thrive (91.4%), developmental delay (79.3%), and dehydration episodes (72.4%). Most children showed marked improvement in growth parameters in response to appropriate management, except for cases with Fanconi syndrome. Last, only one case (with cystinosis) developed end-stage kidney disease. HRTD (most commonly distal RTA and Bartter syndrome) could be relatively common among Egyptian children, and the diagnosis seems challenging and often delayed.

Hypokalemic paralysis due to distal renal tubular acidosis type 1 in patient of mucormycosis on amphotericin B: a case report

A 42-year-old male patient who is a known case of DM and mucormycosis on treatment presented with sudden onset difficulty in moving all 4 limbs followed by decreased depth of respiration for 4 hours. The patient was known case of DM for 10 years and was on OHA for the same, he had history of biopsy diagnosed rhino mucormycosis 4 months ago and was on treatment for the same. On initial examination the tone was hypotonic in all4 limbs along with power of 3+, respiration was shallow and patient was bedridden unable to stand on his own, he was ambulatory 6 days before presenting to hospital. Potassium-1.7 mEq/l, ABGA pH-7.18, HCO3-10 Meq/l, urine osmolality 220 mOsm/l, urine pH-7.0, potassium-to-creatinine rstio (K/Cr)-3.9 mEq/ml, urine K-22 mEq/ml. Distal RTA (dRTA) is the classical form of RTA, being the first described. Distal RTA is characterized by a failure of H+ secretion into lumen of nephron by the alpha intercalated cells of the medullary collecting duct of the distal nephron. This failure of acid secretion may be due to a number of causes, and it leads to an inability to acidify the urine to a pH of less than 5.3. This case study enumerates the potentially dangerous side effects of amphotericin B in patients which can precipitate RTA type 1 leading to severe hypokalaemia and acidosis, thus all patients receiving amphotericin B should be cautiously warned regarding side effect of hypokalaemia and prophylactic potassium syrup supplementation may be given in predisposed patients.

122 Rhabdomyolysis as the Initial Presentation of Distal (Type 1) RTA

122 Rhabdomyolysis as the Initial Presentation of Distal (Type 1) RTA

107 Tenofovir-Induced Distal RTA and Nephrogenic DI

107 Tenofovir-Induced Distal RTA and Nephrogenic DI

Phenotype and Genotype Profile of Children with Primary Distal Renal Tubular Acidosis: A 10-Year Experience from a North Indian Teaching Institute.

Primary distal renal tubular acidosis (dRTA) or Type 1 RTA in children is caused by a genetic defect (involved genes ATP6V0A4 , ATP6V1B1 , SLC4A1 , FOXI1 , or WDR72 ), which causes tubular transport defects characterized by an inability to appropriately acidify urine with resultant persistent hyperchloremic metabolic acidosis. Retrospective analysis of 28 children (14 males) under the age of 14 years with dRTA seen from 2010 to 2019 was reviewed, and detailed clinic records were analyzed. The clinical features, investigations, and response to treatment were recorded. The median age of the children at presentation was 30 months (range: 9.25-72 months), and the median age at onset of symptoms was 2 months. All the children had growth failure, polyuria, and polydipsia at presentation. Mean serum potassium, pH, bicarbonate, and anion gap at presentation was 2.3 ± 0.5 mmol/L, 7.22 ± 0.09, 13.28 ± 4.37 mmol/L, and 9.3 ± 2.18, respectively. Mean serum potassium, pH, bicarbonate at follow-up was 3.88 ± 0.6 mmol/L, 7.35 ± 0.06, and 20.13 ± 4.17 mmol/L, respectively. The median z-score for the weight for age and height for age at initial presentation was -4.77 (-7.68 to -3.74) and -4.21 (-5.42 to -2.37) and at follow-up was -3.35 (-5.29 to -1.55) and -3.84 (-5.36 to -1.63), respectively. Twenty-two (78.6%) children had medullary nephrocalcinosis. Four children had sensorineural hearing loss. Seven children had genetic testing done, and six had pathogenic or likely pathogenic variants in ATP6V1B1 and ATP6V0A4 gene. Children with dRTA have a guarded prognosis and ATP6V1B1 and ATP6V0A4 mutations are the most common implicated genetic defect in Indian children with distal RTA.

Distal RTA with Hypokalemic Quadriparesis as the Initial Presentation of Primary Sjogren's Syndrome

Sjogren syndrome (SS) is a multisystemic autoimmune disorder with predominant exocrine gland involvement leading to sicca symptoms. Among extraglandular manifestations, renal involvement is commonly seen. Renal involvement can be either tubulointerstitial (TIN) or glomerular, the former being more common.

Type 1 diabetes mellitus presenting as distal renal tubular acidosis (type 1)

A 42 year-old male patient known case of type 1 diabetes mellitus for last 15 years got admitted with bilateral lower limb swelling and poorly controlled diabetes. He was found to have alkaline urinary pH, persistent metabolic acidosis even after the correction of blood sugars without ketonuria or diabetic ketoacidosis and nephrocalcinosis thus he was diagnosed as distal renal tubular acidosis (RTA Type 1) and managed by alkali replacement with blood sugar control. The association of type-1 diabetes mellitus with type-1 RTA has been rarely reported in the literature, but there are various case reports which had linked with distal RTA with autoimmunity and destruction of DCT. As our case which was unusual as every type-1 diabetes doesn’t have acidosis due to DKA focused research is required in this field.

P0058THE ROLE OF GENETICS IN INCOMPLETE DISTAL RENAL TUBULAR ACIDOSIS IN NEPHROLITHIASIS

Abstract Background and Aims Distal renal tubular acidosis (dRTA) is characterized by an impairment of urinary acidification resulting in a hyperchloremic non-anion gap metabolic acidosis, hypokalemia and inappropriately elevated urine pH. If not treated, this chronic condition eventually leads to nephrocalcinosis and recurrent nephrolithiasis, impaired renal function and bone demineralization due to reabsorption of bicarbonate and phosphate complexed with calcium from the bone as a buffer for metabolic acidosis. Distal RTA is therefore a well-defined entity that can be diagnosed by genetic testing of five genes known to be disease-causative (ATPV1B1 and ATPV0A4, FOXi1, SLC4A1 and WDR72). Incomplete distal renal tubular acidosis (idRTA) is defined as impaired urinary acidification that does not lead to overt metabolic acidosis and therefore can be diagnosed if patients fail to adequately acidify urine after an ammonium chloride (NH4Cl) challenge or other acid load tests. It is observed in 10-20% of calcium stone formers. It is still uncertain whether idRTA represents a distinct entity or it is part of the dRTA spectrum and whether it is caused by mutations in the same genes of overt dRTA. Heterozygous ATP6V1B1 pathogenic variants have been linked to idRTA, as well as mutations in SLC4A1. Method In this cross-sectional study we investigated a group of 23 stone formers whose clinical features were suspicious of idRTA: a history of nephrolithiasis or nephrocalcinosis with morning urinary pH &amp;gt; 5.8 in the absence of overt metabolic acidosis. They therefore underwent a simplified NH4Cl challenge and were found to have impaired urinary acidification ability. These patients were then analyzed by genetic testing with sequencing of 4 genes: SLC4A1, ATP6V1B1, ATP6V0A4 and FOXi1. Results Two unrelated individuals were found to have mutations in SLC4A1: 2 different variants in heterozygosis that had never been described before. The first patient was a 47-year old man, recurrent stone former (mainly apatite, but also some calcium oxalate), with hypercalciuria but normal bone mineral density (BMD). His family history revealed 1 uncle with kidney stones. The second patient was a 56-year old woman with a diagnosis of osteogenesis imperfecta, a history of reduced BMD and severe restrictive ventilation disorder and passed 1 stone (35% apatite, 65% CaOx). She was found to have bilateral nephrocalcinosis and hypocitraturia. Her family history revealed a sister with kidney stones. Conversely, 21 patients did not show any mutations for the genes sequenced, leading to a prevalence of genetic mutations of 8.7%. This is a much lower figure compared with overt dRTA, in which only 30% of patients with a clinical diagnosis of hereditary dRTA have no identified causative mutations in the currently known genes. Conclusion This suggests the involvement of other genes (WDR72 or others) or non-genetic tubular dysfunction in the pathogenesis of idRTA in stone formers.

Etiological Profile of Nephrocalcinosis in Children from Southern India

To study the etiological profile and patterns of clinical presentation of nephrocalcinosis. In this observational study, patients 18 years or younger, referred to the pediatric nephrology clinic with nephrocalcinosis were evaluated for etiology. Symptoms/signs at presentation, estimated glomerular filtration rate (eGFR) at presentation and follow-up, and growth parameters were recorded. The etiology of nephrocalcinosis (n=54) included distal renal tubular acidosis (n=18; 33.3%), primary hyperoxaluria (n=9; 16.7%), Bartter syndrome (n=7; 13%), Dent disease (n=4; 7.4%), cystinosis, familial hypomagnesemia with hypercalciuria and idiopathic hypercalcemia of infancy (2 each). Idiopathic nephrocalcinosis was seen in 5 (9.3%) children. Clinical features included failure to thrive (53.7%), polyuria (44.4%), bony deformities (31.5%) and hypokalemic paralysis (11.1%). At a median (IQR) follow-up of 24 (8, 56) months, the mean (SD) eGFR had improved from 59 (25.5) to 77 (31.48) mL/min/1.73m2 (P<0.01). Consanguinity was present in 50% (27/54). Genetic analysis in 5 primary hyperoxaluria cases confirmed AGXT mutations in 4; and GRHPR mutation in 1 child. Distal RTA, primary hyperoxaluria and Bartter syndrome were the common etiologies of nephrocalcinosis in our patient population.

C-Terminal Fibroblast Growth Factor-23 Levels in Non-Nutritional Hypophosphatemic Rickets.

Fibroblast growth factor-23 (FGF23) is central to phosphate homeostasis. The author examined if blood levels of FGF23 allow discrimination of classic hypophosphatemic ricketsfrom other causes of non-nutritional rickets with hypophosphatemia. Forty-two children (median age:102 mo) with non-nutritional rickets and hypophosphatemia were clinically classified as having distal renal tubular acidosis (RTA, n = 12), Fanconi syndrome (n = 8), classic hypophosphatemic rickets (n = 11), vitamin D dependent rickets (n = 7) and Dent disease (n = 4). Median blood FGF23 (measured by C-terminal ELISA) concentrations were similar in all groups (P = 0.24). These levels did not correlate with phosphate, tubular maximum for phosphate, calcium, 25-hydroxyvitamin D, creatinine, and parathormone levels. Patients with distal RTA showed variable degree of proximal tubular dysfunction that resolved following alkali supplements. Blood FGF23 levels did not satisfactorily differentiate classic hypophosphatemic rickets from other causes of hypophosphatemic rickets.

Osteomalacia Induced by Renal Tubular Acidosis Type 1

Renal Tubular Acidosis, a group of disorders characterized by defective renal acid-base regulation, can impair mineralization of bone matrix in adults known as osteomalacia. RTA is classified into 3 major forms, such as proximal RTA or type 2; distal RTA or type 1; and hyperkalemic RTA or type 4. Among all type of RTA, proximal RTA or type 2 is known have association with Fanconi syndrome and bone involvement. However, distal RTA or type 1 can also cause osteomalacia. Hereby we report a case of 22 years old Asian woman who wasfirstly diagnosed with distal type RTA several years ago then started developing bone involvement recently. She was complaining with low back pain due to fracture on left medial side of inferior pubic ramus and endplate fracture on right side superior L4 and BMD examination showed low mineral density. She was diagnosed with osteomalacia induced by distal type RTA due to the loss of calcium salts from bone and hypophosphatemia.Keywords: Osteomalacia; Renal Tubular Acidosis; Hypokalemia; Hypophosphatemia

Changes in V-ATPase subunits of human urinary exosomes reflect the renal response to acute acid/alkali loading and the defects in distal renal tubular acidosis

In the kidney, final urinary acidification is achieved by V-ATPases expressed in type A intercalated cells. The B1 subunit of the V-ATPase is required for maximal urinary acidification, while the role of the homologous B2 subunit is less clear. Here we examined the effect of acute acid/alkali loading in humans on B1 and B2 subunit abundance in urinary exosomes in normal individuals and of acid loading in patients with distal renal tubular acidosis (dRTA). Specificities of B1 and B2 subunit antibodies were verified by yeast heterologously expressing human B1 and B2 subunits, and murine wild-type and B1-deleted kidney lysates. Acute ammonium chloride loading elicited systemic acidemia, a drop in urinary pH, and increased urinary ammonium excretion. Nadir urinary pH was achieved at four to five hours, and exosomal B1 abundance was significantly increased at two through six hours after ammonium chloride loading. After acute equimolar sodium bicarbonate loading, blood and urinary pH rose rapidly, with a concomitant reduction of exosomal B1 abundance within two hours, which remained lower throughout the test. In contrast, no change in exosomal B2 abundance was found following acid or alkali loading. In patients with inherited or acquired distal RTA, the urinary B1 subunit was extremely low or undetectable and did not respond to acid loading in urine, whereas no change in B2 subunit was found. Thus, both B1 and B2 subunits of the V-ATPase are detectable in human urinary exosomes, and acid and alkali loading or distal RTA cause changes in the B1 but not B2 subunit abundance in urinary exosomes.

A case report of distal RTA presenting as hypokalaemic periodic paralysis in young male

A 21-year-old normotensive male presented with acute onset flaccid paralysis with the history of a similar episode a few months back. Clinical and laboratory evaluation revealed lower motor neuron type of flaccid quadriparesis with hypokalaemia, normal anion gap metabolic acidosis, bicarbonaturia, and transtubular potassium concentration gradient (TTKG) more than 7. Subsequently urine acidification test (by NH4CI challenge test) was done and diagnosis of distal renal tubular acidosis was established. The patient responded to conservative management (Sohl's solution).

Deficient acid handling with distal RTA in the NBCe2 knockout mouse.

In many circumstances, the pathogenesis of distal renal tubular acidosis (dRTA) is not understood. In the present study, we report that a mouse model lacking the electrogenic Na(+)-HCO3 (-) cotransporter [NBCe2/Slc4a5; NBCe2 knockout (KO) mice] developed dRTA after an oral acid challenge. NBCe2 expression was identified in the connecting tubule (CNT) of wild-type mice, and its expression was significantly increased after acid loading. NBCe2 KO mice did not have dRTA when on a standard mouse diet. However, after acid loading, NBCe2 KO mice exhibited complete features of dRTA, characterized by insufficient urinary acidification, hyperchloremic hypokalemic metabolic acidosis, and hypercalciuria. Additional experiments showed that NBCe2 KO mice had decreased luminal transepithelial potential in the CNT, as revealed by micropuncture. Further immunofluorescence and Western blot experiments found that NBCe2 KO mice had increased expression of H(+)-ATPase B1 in the plasma membrane. These results showed that NBCe2 KO mice with acid loading developed increased urinary K(+) and Ca(2+) wasting due to decreased luminal transepithelial potential in the CNT. NBCe2 KO mice compensated to maintain systemic pH by increasing H(+)-ATPase in the plasma membrane. Therefore, defects in NBCe2 can cause dRTA, and NBCe2 has an important role to regulate urinary acidification and the transport of K(+) and Ca(2+) in the distal nephron.

Tubular dysfunction in renal transplant patients using sirolimus or tacrolimus

Tubular dysfunction is prevalent among kidney transplant patients using calcineurin inhibitors, but our knowledge of the tubular effects of mTOR inhibitors is more limited. 60 kidney transplant outpatients using either the calcineurin inhibitor tacrolimus or the mTOR inhibitor sirolimus were investigated for renal tubular dysfunction. Proximal tubule function was assessed by quantification of albumin and β2-microglobulin, tubular reabsorption of phosphate and fractional excretion of bicarbonate. Distal tubular function was evaluated by water deprivation test and by urinary acidification test using furosemide and fludrocortisone for pH, ammonium and titratable acidity measurements. The prevalence of distal renal tubular acidosis (dRTA) was 17% for both treatment groups. 70% of patients treated with sirolimus and 94% using tacrolimus presented with urine concentrating defect (p=0.04). Distal RTA and urine concentrating defect were highly prevalent after kidney transplantation both in the sirolimus and tacrolimus treated patients. Acidification test was essential for the appropriate diagnosis of dRTA while dipstick urine specific gravity test was able to detect urine concentrating defect in this population.

AB0559 Hypokalemic Paralysis in Primary Sjogren Syndrome: is IT A Distinct Clinical Subset Which Requires Lifelong Potassium Supplementation Rather than Immunosuppressants?

BackgroundPrimary Sjögren's syndrome (pSS) is a systemic autoimmune disorder with predominant involvement of exocrine glands in middle aged females. It may involve extra-glandular tissues such as lung, liver, kidney, pancreas,...