A physiology-based approach to a patient with hyperkalemic renal tubular acidosis / Abordagem diagnóstica de um paciente com acidose tubular renal hipercalêmica

ABSTRACT Hyperkalemic renal tubular acidosis is a non-anion gap metabolic acidosis that invariably indicates an abnormality in potassium, ammonium, and hydrogen ion secretion. In clinical practice, it is usually attributed to real or apparent hypoaldosteronism caused by diseases or drug toxicity. We describe a 54-year-old liver transplant patient that was admitted with flaccid muscle weakness associated with plasma potassium level of 9.25 mEq/L. Additional investigation revealed type 4 renal tubular acidosis and marked hypomagnesemia with high fractional excretion of magnesium. Relevant past medical history included a recent diagnosis of Paracoccidioidomycosis, a systemic fungal infection that is endemic in some parts of South America, and his outpatient medications contained trimethoprim-sulfamethoxazole, tacrolimus, and propranolol. In the present acid-base and electrolyte case study, we discuss a clinical approach for the diagnosis of hyperkalemic renal tubular acidosis and review the pathophysiology of this disorder.

RESUMO A acidose tubular renal hipercalêmica é uma acidose metabólica de ânion gap normal que invariavelmente indica anormalidade na secreção de íons potássio, amônio e hidrogênio. Na prática clínica, está geralmente atribuída a um estado de hipoaldosteronismo real ou aparente, causado por doenças ou toxicidade por drogas. Descrevemos um paciente de 54 anos, transplantado hepático, que foi admitido com fraqueza muscular associada à hipercalemia, potássio plasmático de 9,25 mEq/L. A investigação adicional revelou acidose tubular renal tipo 4 e importante hipomagnesemia com elevada fração de excreção de magnésio. A história patológica pregressa incluía um diagnóstico recente de Paracoccidioidomicose - uma infecção sistêmica fúngica endêmica que ocorre em algumas partes da América do Sul -, e as medicações de uso habitual continham sulfametoxazol-trimetoprim, tacrolimus e propranolol. No presente relato de caso, discutiremos uma abordagem clínico-laboratorial para o diagnóstico da acidose tubular renal hipercalêmica, assim como da hipomagnesemia, revisando a fisiopatologia desses transtornos.

Sequenciamento total do exoma como ferramenta de diagnóstico de acidose tubular renal distal / Whole-exome sequencing as a diagnostic tool for distal renal tubular acidosis

Resumo Objetivo A acidose tubular renal distal (ATRd) é caracterizada por acidose metabólica devido à excreção renal de ácido prejudicada. O objetivo deste artigo é apresentar o diagnóstico genético de quatro crianças com ATRd com uso do sequenciamento total do exoma. Métodos Selecionamos duas famílias não relacionadas, quatro crianças com ATRd e seus pais, para fazer o sequenciamento total do exoma. A audição foi preservada em ambas as crianças da família um, porém em nenhuma criança da família dois, na qual um par de gêmeas teve perda auditiva severa. Fizemos o sequenciamento total do exoma em dois conjuntos de amostras e confirmamos os achados com o método de sequenciamento de Sanger. Resultados Duas mutações foram identificadas nos genes ATP6V0A4 e ATP6V1B1. Na família um, detectamos uma nova mutação no éxon 13 do gene ATP6V0A4 com uma alteração em um nucleotídeo único GAC → TAC (c.1232G>T) que causou substituição de ácido aspártico por tirosina na posição 411. Na família dois, detectamos uma mutação recorrente do homozigoto com inserção de um par de bases (c.1149_1155insC) no éxon 12 do gene ATP6V1B1. Conclusão Nossos resultados confirmam o valor do sequenciamento total do exoma para o estudo de nefropatias genéticas complexas e permitem a identificação de mutações novas e recorrentes. Adicionalmente, demonstramos claramente pela primeira vez a aplicação desse método molecular em doenças tubulares renais.

Abstract Objective Distal renal tubular acidosis (dRTA) is characterized by metabolic acidosis due to impaired renal acid excretion. The aim of this study was to demonstrate the genetic diagnosis of four children with dRTA through use of whole-exome sequencing. Methods Two unrelated families were selected; a total of four children with dRTA and their parents, in order to perform whole-exome sequencing. Hearing was preserved in both children from the first family, but not in the second, wherein a twin pair had severe deafness. Whole-exome sequencing was performed in two pooled samples and findings were confirmed with Sanger sequencing method. Results Two mutations were identified in the ATP6V0A4 and ATP6V1B1 genes. In the first family, a novel mutation in the exon 13 of the ATP6V0A4 gene with a single nucleotide change GAC → TAC (c.1232G>T) was found, which caused a substitution of aspartic acid to tyrosine in position 411. In the second family, a homozygous recurrent mutation with one base-pair insertion (c.1149_1155insC) in exon 12 of the ATP6V1B1 gene was detected. Conclusion These results confirm the value of whole-exome sequencing for the study of rare and complex genetic nephropathies, allowing the identification of novel and recurrent mutations. Furthermore, for the first time the application of this molecular method in renal tubular diseases has been clearly demonstrated.

Electrolyte Imbalances and Nephrocalcinosis in Acute Phosphate Poisoning on Chronic Type 1 Renal Tubular Acidosis due to Sjogren's Syndrome

Although renal calcium crystal deposits (nephrocalcinosis) may occur in acute phosphate poisoning as well as type 1 renal tubular acidosis (RTA), hyperphosphatemic hypocalcemia is common in the former while normocalcemic hypokalemia is typical in the latter. Here, as a unique coexistence of these two seperated clinical entities, we report a 30-yr-old woman presenting with carpal spasm related to hypocalcemia (ionized calcium of 1.90 mM/L) due to acute phosphate poisoning after oral sodium phosphate bowel preparation, which resolved rapidly after calcium gluconate intravenously. Subsequently, type 1 RTA due to Sjogren's syndrome was unveiled by sustained hypokalemia (3.3 to 3.4 mEq/L), persistent alkaline urine pH (> 6.0) despite metabolic acidosis, and medullary nephrocalcinosis. Through this case report, the differential points of nephrocalcinosis and electrolyte imbalances between them are discussed, and focused more on diagnostic tests and managements of type 1 RTA.

Application of molecular methods of genetic counseling in inherited forms of renal tubular acidosis for preventive strategy

Renal tubular acidosis [RTA] results from failure of the kidney to acidify the urine resulting in a state of hyperchloraemic metabolic acidosis with a normal anion gap. Three main clinical types of RTA are now recognized [proximal, distal and hyperkalemic] but the number of possible causes is large. Inherited forms of distal RTA have three variants: autosomal dominant and autosomal recessive with or without deafness, while the inherited forms of proximal RTA include many variants as autosomal recessive proximal RTAt cystinosis, Fanconi-Bickel syndrome [FBS] and Wilson's disease. Thus, we conducted a prospective study to screen all the documented cases of inherited RTA in pediatric nephrology outpatient clinic in MUCH for relevant gene mutation. This study was carried out in the period from November 2009 to February 2012. The study comprised 17 Egyptian families having documented cases of inherited RTA. We found three families compatible with the clinical diagnosis of FBS, two families compatible with the clinical diagnosis of cystinosis and 12 families of dRTA. All patients were subjected to a thorough history, full clinical examination and laboratory investigations. Pedigree construction was done for each family. Radiological investigations were done for some cases including plain x-ray for racketic findings, abdominal ultrasound and echocardiography done for those with clinical findings coping with congenital or acquired heart diseases. Liver biopsy was done for those with hepatomegaly. Molecular workup was done in the form of DNA extraction, agarose gel electrophoresis, polymerase chain reaction of the extracted DNA and sequencing for the specific gene according to each disease. We found two new mutations in GLUT2 gene and an old missense mutation [re-enumerated] in three families of FBS. We found a novel truncating mutation in CTNS gene associated with a severe clinical course and double heterozygosity for two known mutations in the other family. Two novel mutations were detected in two out of 12 families of dRTA in ATP6VOA4 gene. We concluded that although these diseases are not rare in the Egyptian population, evolving new mutations could add some allelic variants. Moreover, studying phenotype-genotype pattern of different mutations is crucial for linkage analysis

Distal renal tubular acidosis, hypokalemic paralysis, nephrocalcinosis, primary hypothyroidism, growth retardation, osteomalacia and osteoporosis leading to pathological fracture: a case report

Renal tubular acidosis [RTA] is a constellation of syndromes arising from different derangements of tubular acid transport. Recent advances in the biology of urinary acidification have allowed us to discern various molecular mechanisms responsible for these syndromes. RTA often presents as renal stone disease with nephrocalcinosis, ricket/osteomalacia and growth retardation in children with ultimate short stature in adulthood. The case reported here has features of distal renal tubular acidosis [dRTA], hypokalemic paralysis, primary hypothyroidism, growth retardation, osteomalacia and osteopenia leading to stress fracture. All these features presenting in a single case [as in our case] is a rare occurrence, so far other cases of distal renal tubular acidosis [dRTA] have been reported

Distal renal tubular acidosis and its relationship with hearing loss in children: preliminary report

In autosomal recessive distal renal tubular acidosis [DRTA], a substantial fraction of the patients have progressive bilateral sensorineural hearing loss. This coexistence is due to the mutations of a gene expressed both in the kidney and in the cochlea. The aim of this study was to assess the correlation between hearing loss and DRTA. In this study, 51 children diagnosed with renal tubular acidosis were evaluated. Diagnosis of DRTA was based on clinical manifestations and detection of normal anion gap metabolic acidosis, urine pH higher than 5.5, and positive urinary anion gap. Audiometry was performed in children with DRTA and sequencing of the ATP6V1B1 gene was done for those with sensorineural hearing loss. Twenty-seven patients [52.9%] had DRTA, of whom 51.9% were younger than 1 year old, 55.6% were boys, and 44.4% were girls. Eleven patients [40.7%] had bilateral sensorineural hearing loss, consisting of 5 of 15 boys [33.3%] and 6 of 12 girls [50.0%]. There was no correlation between hearing loss and gender. Three patients with hearing loss had mutation in the ATP6V1B1 gene [11.1% of patients with DRTA and 27.3% of patients with DRTA and hearing loss]. This study indicated that a significant percentage of the children with DRTA had sensorineural hearing loss and mutation in ATP6V1B1 gene. It is recommended to investigate hearing impairment in all children with DRTA

Arthrogryposis, renal tubular dysfunction and cholestasis [ARC] syndrome: a case report

Arthrogryposis, renal tubular dysfunctions and chloestasis [ARC] syndrome is a rare multisystem, usually fatal, autosomal recessive disorder. Awareness of this syndrome is growing with more reported cases over the last three decades. Many previously reported cases with similar association are now labeled as ARC syndrome. Although the genetic mutation is recently recognized, the diagnosis still depends on the clinical findings. Our patient is the first case of ARC syndrome to be reported from Kuwait. To the best of our knowledge this is also the first report of an Egyptian family with two siblings of ARC syndrome

Carbonic anhydrase II deficiency: A novel mutation.

Carbonic anhydrase II (CA II) deficiency is an extremely rare autosomal recessive disorder, characterised by a triad of osteopetrosis, renal tubular acidosis and cerebral calcifications. A 12-year-old boy with classical features of CA II deficiency is reported who was found to be homozygous for the mutation in CA II gene and parents were heterozygous for the same mutation .To the best of our knowledge this is the first case report of mutation proven CA II deficiency from India.

Distúrbios ácido-base na leishmaniose visceral / Acid-base disorders in visceral leishmaniasis

Defeitos na capacidade de acidificação e concentração urinárias têm sido descritos em pacientes portadores de leishmaniose visceral. Foram avaliados os distúrbios do equilíbrio ácido-base presentes nos pacientes com calazar, bem como os fatores relacionados. Metodologia: Foram estudados 59 pacientes com formas crônicas de calazar e comparados a um grupo controle. A gasometria arterial foi colhida em jejum; o pH urinário, a acidez titulável e a amônia urinária foram determinadas em urinas colhidas sob óleo mineral. A amônia foi dosada pela técnica de Berthelot e a acidez titulável, pela técnica de Palmer. Resultados: Todos os pacientes tinham hipoalbuminemia, hipergamaglobulimenia e hiponatremia. O grupo I compreendeu 75,5% dos pacientes, que apresentaram quadro misto de alcalose respiratória e alcalose metabólica. Hipocloremia ocorreu em 37,6%; hipocalemia associada a um potássio urinário elevado foi observada em 24,8% dos casos. Hipomagnesemia com perda renal de magnésio e potássio foi detectada em 44% dos casos. O grupo II, constituído por 24,5% dos pacientes, apresentou quadro de acidose metabólica. A excreção urinária de H+, a acidez titulável e a amônia foram semelhantes nos dois grupos. Um elevado pH urinário e uma carga elétrica urinária positiva confirmaram no grupo II a presença de acidose tubular renal distal. O equilíbrio ácido-base, pelo modelo stewart-Figge, mostra diminuição da diferença de íons fortes (SIDa), elevação do SIG e diminuição da concentração de ácidos fracos. Conclusões: Alcalose respiratória crônica e alcalose metabólica associada 9grupo I) foram observadas em 75.5% dos casos e relacionaram-se com o quadro de pneumonite intersticial, anemia, febre e disfunção hepática. Hipomagnesemia com depleção de potássio e magnésio estava presente.

Defects in the ability of urinary acidification and concentration have been described in patients with visceral leishmaniasis. We assessed disorders present acid-base balance in patients with kala-azar, as well as the related factors. Methodology: We studied 59 patients with chronic forms of leishmaniasis and compared to a control group. The arterial blood gas was collected in fasting, urinary pH, titratable acidity and urinary ammonium were determined in urine collected under mineral oil. Ammonia was measured by the Berthelot technique and acidity, the technique of Palmer. Results: All patients had hypoalbuminemia, and hyponatremia hipergamaglobulimenia. Group I comprised 75.5% of patients, who had mixed picture of respiratory alkalosis and metabolic alkalosis. Hypochloremia occurred in 37.6%, hypokalemia associated with a high urinary potassium was observed in 24.8% of cases. Hypomagnesemia with renal loss of magnesium and potassium was detected in 44% of cases. Group II, consisting of 24.5% of patients presented with metabolic acidosis. The urinary excretion of H +, acidity and ammonia were similar in both groups. A high urinary pH and urinary a positive electric charge in the group II confirmed the presence of distal renal tubular acidosis. The acid-base balance by Stewart-Figge model shows decrease in strong ion difference (AIDS), an increase of GIS and decreased concentration of weak acids. Conclusions: Chronic respiratory alkalosis and metabolic alkalosis associated 9grupo I) were observed in 75.5% of cases and were related to the picture of interstitial pneumonitis, anemia, fever and liver dysfunction. Hypomagnesemia with depletion of potassium and magnesium was present. Metabolic acidosis (group II) was observed in 24.5% of patients presenting with.

Metabolic acidosis.

Acute metabolic acidosis is frequently encountered in critically ill patients. Metabolic acidosis can occur as a result of either the accumulation of endogenous acids that consumes bicarbonate (high anion gap metabolic acidosis) or loss of bicarbonate from the gastrointestinal tract or the kidney (hyperchloremic or normal anion gap metabolic acidosis). The cause of high anion gap metabolic acidosis includes lactic acidosis, ketoacidosis, renal failure and intoxication with ethylene glycol, methanol, salicylate and less commonly with pyroglutamic acid (5-oxoproline), propylene glycole or djenkol bean (gjenkolism). The most common causes of hyperchloremic metabolic acidosis are gastrointestinal bicarbonate loss, renal tubular acidosis, drugs-induced hyperkalemia, early renal failure and administration of acids. The appropriate treatment of acute metabolic acidosis, in particular organic form of acidosis such as lactic acidosis, has been very controversial. The only effective treatment for organic acidosis is cessation of acid production via improvement of tissue oxygenation. Treatment of acute organic acidosis with sodium bicarbonate failed to reduce the morbidity and mortality despite improvement in acid-base parameters. Further studies are required to determine the optimal treatment strategies for acute metabolic acidosis.

Acidose tubular renal em pediatria: [revisão] / Renal tubular acidosis in pediatrics: [review]

O termo Acidose Tubular Renal (ATR) engloba diversas afecções caracterizadas por acidose metabólica secundária a um defeito na reabsorção tubular renal de HCO 3- e/ou na excreção urinária de H+, enquanto a função glomerular é nada ou minimamente afetada. Todas as formas de ATR apresentamacidose metabólica hiperclorêmica, com intervalo aniônico normal. São doenças crônicas com impacto significativo na qualidade de vida dos pacientesquando não tratadas adequadamente, podendo evoluir com déficit do crescimento, osteoporose, raquitismo, nefrolitíase e até perda da função renal.Podem ser primárias, decorrentes de defeitos genéticos nos mecanismos de transporte dos túbulos renais, ou secundárias a doenças sistêmicas ou aoefeito adverso de medicamentos. Neste artigo, é feita uma breve revisão da homeostase ácido-básica pelo rim, discutindo-se, a seguir, aspectos dafisiopatologia, diagnóstico e abordagem das acidoses tubulares renais em pediatria.

The term Renal Tubular Acidosis (RTA) defines many disorders characterized by metabolic acidosis, secondary to defects in renal tubular reabsorption ofHCO3 - and/or in urinary excretion of H+, while glomerular function is little or not affected. All forms of RTA present hyperchloremic metabolic acidosis, witha normal anion gap. When not adequately treated, these chronic diseases can have a significant impact on the quality of life of affected patients, and can evolve into growth failure, osteoporosis, rickets, nephrolithiasis and even renal insufficiency. These disorders can be primary, originating from genetic defectson tubular transport mechanisms, or can be secondary to systemic diseases and to adverse drug reactions. In this article, the mechanisms of acid-baseregulation by the kidney are briefly reviewed, followed by a presentation of the latest evidence regarding physiopathology, diagnosis and management ofrenal tubular acidosis in pediatric patients.

Primary Sjö-gren's syndrome presenting with distal, renal tubular acidosis and rhabdomyolysis.

Primary Sjögren's syndrome (PSS) is rare in India. Clinically manifest renal disease in PSS is uncommon and is usually an autoimmune tubulointerstitial nephritis presenting with distal renal tubular acidosis (dRTA) or a urinary concentrating defect. Hypokalemic paralysis due to dRTA in PSS is rare but well documented in medical literature. Rhabdomyolysis as a consequence of hypokalemia in PSS is exceptional. We report a case of PSS with dRTA and rhabdomyolysis causing prolonged respiratory failure and quadriparesis.

H+_Atpasa Vacuolar Renal. Fisiología y Regulación / Vacuolar H (+)_ATPase renal. Physiologi and Regulation

Las H+ _ATPasas vacuolares son complejos proteicos ubicuos con múltiples subunidades que incluyen un dominio catalítico V1 compuesto por proteínas periféricas que hidrolizan adenosina trisfosfato (ATP) y proveen energía a la bomba de H+ a través de un segundo dominio transmembrana Vº en contra de importantes gradientes. Estas H+_ATPasas vacuolares, que intervienen en la translocación de protones, son responsables en células eucariotas de la acidificación de las organelas intracelulares y de la acidificación de los espacios luminales e intersticiales adyacentes a las membranas plasmáticas celulares. Mutaciones en los genes que codifican las subunidades de H+ATPasa vacuolar específicas de células intercalares de ríñón; Vºa4 y V1B1, causan el síndrome de acidosis tubular distal renal. Esta revisión se focalizará en función, regulación y en el rol de H+ATPasa vacuolar en fisiología renal. La localización de H+ _ATPasa en el rión y su rol en la regulación de pHintracelular, transporte de protones y la homostsis del ácido base, será discutida.

Congenital central hypoventilation with renal tubular acidosis

CCHS presents as hypoventilation, mainly in depth rather than rate of breathing, manifest mainly in quiet sleep; however in severe cases, even in awake period. Hirschprung disease is high in the list of associated anomaly as high as 30% in one report and neuroblastoma as 20%. Although, eye anomalies, developmental delay, seizures, hearing defects, GIT motility disorders have been linked as other associated findings, renal tubular defect seems to be unusual and should be looked for also. Management of CCHS is difficult and challenging with guarded prognosis although some families would not continue the treatment for ever

Topiramate and severe metabolic acidosis: case report

Topiramato pode produzir raramente uma acidose metabólica através da inibição da anidrase carbônica no túbulo distal do néfron - acidose tubular renal do tipo 2. Relatamos o caso de mulher de 40 anos previamente saudável que desenvolveu quadro de acidose metabólica assintomática grave, sem outra etiologia identificável, durante uso de topiramato na dose de 100mg/dia por três meses. Este efeito colateral, embora infrequente, parece ser imprevisível e requer atenção cuidadosa.