Esotropia, nystagmus and optic disk staphyloma in Donnai-Barrow syndrome / Esotropia, nistagmo e estafiloma de disco óptico na síndrome de Donnai-Barrow

ABSTRACT A 12-year-old boy with Donnai-Barrow syndrome diagnosed intra-uterus presented esotropia, high myopia, nystagmus, and optic disk staphyloma in an ophthalmologic examination. The patient had associated Fanconi syndrome and sensorineural hearing loss as well as facial manifestations as hypertelorism, downward slanting of palpebral fissures and low ear implantation. Magnetic resonance imaging revealed agenesis of the corpus callosum. To our knowledge, this is the first reported case associated with esotropia, nystagmus, and optic disk staphyloma.

RESUMO Paciente do sexo masculino, 12 anos, com diagnóstico intrauterino de síndrome de Donnai-Barrow, apresentava ao exame oftalmológico esotropia, alta miopia, nistagmo e estafiloma de disco óptico. Associado ao quadro, apresentava síndrome de Falconi e perda auditiva neurossensorial, além de alterações faciais, como hipertelorismo, inclinação inferior das fissuras palpebrais e implantação baixa das orelhas. Ressonância magnética revelou agenesia de corpo caloso. Ao nosso conhecimento, este é o primeiro caso relatado associando esotropia, nistagmo e estafiloma de disco óptico.

Renal tubular acidosis associated with trimethoprim-sulfamethoxazole poisoning / Acidosis tubular renal asociada a intoxicación por trimetoprim-sulfametoxazol

Abstract The combination of trimethoprim-sulfamethoxazole (TMP-SMZ or cotrimoxazole) has a bactericidal effect on gram-positive cocci and gram-negative bacilli. It is used clinically for skin and soft tissue, respiratory and urinary tract infections, and is also relevant for prophylaxis and treatment of opportunistic infections in immunosuppressed patients. Its use at established doses in immunocompetent patients is safe, with a low rate of adverse events. However, in immunosuppressed individuals (human immunodeficiency virus [HIV], transplants, or steroid users), the adverse effects (AEs) of this medication reach 83%; and, when administered parenterally at high doses, lactic acidosis has been documented secondary to the polyethylene glycol vehicle. We present two cases of patients who ingested an overdose of TMP-SMZ and developed type 2 renal tubular acidosis (RTA), which has not been described with this medication, and whose hyperlactatemia is not explained by the polyethylene glycol excipient, as it was taken orally.

Resumen La combinación de trimetoprim-sulfametoxazol (TMP-SMZ o cotrimoxazol) tiene efecto bactericida sobre cocos gram positivos y bacilos gram negativos, con uso clínico en infecciones de piel y tejidos blandos, del tracto respiratorio y urinario, además con relevancia en la profilaxis y tratamiento de infecciones oportunistas en pacientes inmunosupresos. Su uso en pacientes inmunocompetentes a dosis establecidas es seguro, con una baja tasa de eventos adversos. Sin embargo, en población con inmunosupresión: virus de inmunodeficiencia humana (VIH), trasplante, o usuarios de esteroides; los efectos adversos (EA) por este medicamento alcanzan 83% y por administración parenteral en dosis elevadas se ha documentado acidosis láctica secundaria al vehículo polietilenglicol. Presentamos dos casos de pacientes que ingirieron TMP-SMZ en sobredosis, desarrollando acidosis tubular renal (ATR) tipo 2, la cual no se ha descrito en este medicamento y cuya hiperlactatemia no es explicable por el excipiente polietilenglicol debido a que el consumo fue oral.

Atypical clinical presentation of distal renal tubular acidosis: a case report registered in Amazonas, Brazil / Apresentação clínica atípica da acidose tubular renal distal: relato de caso registrado no Amazonas, Brasil

ABSTRACT We report an unusual case of a 24-year-old girl with a history of recurrent hypokalemic paralysis episodes and skin lesions on the lower limbs and buttocks, both of which had an acute evolution. In subsequent investigations, the patient also had nephrocalcinosis, nephrolithiasis, hyperchloremic metabolic acidosis and persistent alkaline urinary pH. The findings were consistent with distal renal tubular acidosis as the cause of hypokalemic paralysis. Clinical findings, immunological tests and the result of skin biopsy suggested primary Sjögren's syndrome as an underlying cause. The patient developed azotemia due to obstructive nephrolithiasis. All the features presented in this case are an unusual manifestation of distal renal tubular acidosis; so far, we are not aware of a similar report in the literature.

RESUMO Relatamos um caso incomum de uma jovem de 24 anos com história de episódios recorrentes de paralisia hipocalêmica e lesões cutâneas em membros inferiores e nádegas, ambas de evolução aguda. Em investigações subsequentes, verificou-se que a paciente apresentava nefrocalcinose, nefrolitíase, acidose metabólica hiperclorêmica e pH urinário persistentemente alcalino. Os achados foram consistentes com acidose tubular renal distal como causa da paralisia hipocalêmica. Achados clínicos, exames imunológicos e o resultado da biópsia de pele foram compatíveis com a síndrome de Sjögren primária como causa subjacente. A paciente evoluiu com azotemia em decorrência da nefrolitíase obstrutiva. Todas as características apresentadas nesse caso são uma manifestação incomum de acidose tubular renal distal; até o momento, não temos conhecimento de um relato semelhante na literatura.

Acidosis tubular renal distal. Serie de casos y revisión narrativa / Distal renal tubular acidosis: case series report and literature review

Resumen La acidosis tubular renal distal es causada por un defecto en la excreción de iones de hidrogeno a nivel tubular distal, lo que aumenta el pH de la orina y disminuye el pH plasmático; esta es una enfermedad con varias manifestaciones clínicas asociadas. En este artículo se hace una revisión profunda sobre la acidosis tubular renal distal y se presenta el caso de tres hermanos (dos hombres y una mujer) con la entidad, siendo este uno de los primeros casos familiares reportados en Colombia. Los tres pacientes recibieron el diagnóstico durante el período de lactancia, presentaron nefrocalcinosis y tuvieron buena respuesta a la terapia con álcali iniciada de forma temprana, logrando eventualmente su suspensión. De manera curiosa, uno de los pacientes también presentó deficiencia de mevalonato quinasa con hiperinmunoglobulinemia D, una alteración no descrita con anterioridad. Esta asociación y la aparente falta de necesidad de continuar el manejo con álcali son atípicas a la luz del conocimiento actual, mereciendo especial consideración.

Abstract The distal renal tubular acidosis presents due to a defect in the excretion of hydrogen ions at the distal tubular level, causing an increase in the pH of the urine and a decrease in the plasma pH, with several associated clinical manifestations. This article makes a thorough review of distal renal tubular acidosis and presents the case of three siblings with the entity, two men and one woman, this being one of the first family cases reported in Colombia. All three received the diagnosis during the lactation period, presented nephrocalcinosis and good response to the alkali therapy started early, eventually achieving their suspension. Interestingly, one of them also presented deficiency mevalonate-kinase with hiperinmunoglobulinemia D, alteration not previously described. This association and the apparent lack of need for continued management with alkali are atypical in the light of current knowledge, deserving special consideration.

The natural history of solitary post-nephrectomy kidney in a pediatric population

ABSTRACT Introduction: Children with a solitary post-nephrectomy kidney (SNK) are at potential risk of developing kidney disease later in life. In response to the global decline in the number of nephrons, adaptive mechanisms lead to renal injury. The aim of this study was to determine the prevalence and time of onset of high blood pressure (HBP), proteinuria, glomerular filtration rate (GFR) disruption and renal tubular acidosis (RTA) in children with SNK. Materials and methods: After obtaining the approval from our institution's ethics committee, we reviewed the medical records of patients under 18 years of age who underwent unilateral nephrectomy between January 2005 and December 2015 in three university hospitals. Results: We identified 43 patients, 35 (81.4%) cases of unilateral nephrectomy (UNP) were due to a non-oncologic pathology and Wilm's tumor was identified in 8 (18.6%) cases. In patients with non-oncologic disease, 9.3% developed de novo hypertension, with an average time of onset of 7.1 years, 25% developed proteinuria de novo, with an average time of onset of 2.2 years. For GFR, 21.8% presented deterioration of the GFR in an average time of 3.4 years. Ten (43.5%) patients developed some type of de novo renal injury after UNP. Patients with oncologic disease developed the conditions slowly and none of them developed proteinuria. Conclusions: Taking into account the high rate of long term postoperative renal injury, it can be considered that nephrectomy does not prevent this disease. The follow-up of children with SNK requires a multidisciplinary approach and long-term surveillance to detect renal injury.

Oral manifestations of renal tubular acidosis associated with secondary rickets: case report / Manifestações bucais da acidose tubular renal associada ao raquitismo secundário: relato de caso

ABSTRACT This report describes the oral manifestations of renal tubular acidosis (RTA) associated with secondary rickets and discusses the biological plausibility of these findings. The characteristic electrolyte changes during RTA or genetic mutations that trigger RTA may be responsible for impaired amelogenesis, dental malocclusion, impacted teeth, and absent lamina dura. This report reinforces the possibility of an association between RTA and the oral manifestations described.

RESUMO Este relato de caso descreve as manifestações bucais da acidose tubular renal (ATR) associada ao raquitismo secundário e discute a plausibilidade biológica desses achados. As alterações eletrolíticas características da ATR ou as mutações genéticas que a desencadeiam podem ser responsáveis pela amelogênese imperfeita, maloclusão dentária, dentes impactados e ausência de lâmina dura. Este relato reforça a possibilidade de uma associação entre ATR e as manifestações bucais descritas.

Acidosis tubular renal distal hereditaria, diagnóstico en hermanos: A propósito de 2 casos pediátricos / Distal hereditary renal tubular acidosis, diagnosis in siblings: About 2 pediatric cases

La acidosis tubular renal distal es el tipo más frecuente de acidosis tubular renal en pediatría y puede ser hereditario. Se debe a una incapacidad del riñón para excretar iones de hidrógeno, en ausencia de deterioro de la función renal, y ocurre con acidosis metabólica hiperclorémica con brecha aniónica (anion gap) normal. Los síntomas pueden ser retraso del crecimiento, vómitos, estreñimiento, falta de apetito, polidipsia y poliuria, nefrocalcinosis, debilidad y hasta parálisis muscular por la hipokalemia. A menudo, se acompaña de deterioro auditivo neurosensorial. Corregir la acidosis puede tener una variedad de beneficios, como restaurar el crecimiento normal, disminuir la hipokalemia, estabilizar o evitar la nefrocalcinosis y disminuir el riesgo de osteopenia. El diagnóstico oportuno y el tratamiento adecuado de los pacientes hacen que permanezcan asintomáticos y sean capaces de llevar una buena calidad de vida. Se presentan los casos de dos hermanos afectados por acidosis tubular renal distal, su proceso diagnóstico, tratamiento y seguimiento actual.

Distal renal tubular acidosis is the most common type of renal tubular acidosis in pediatrics and can be hereditary. It is due to an inability in the kidney to excrete hydrogen ion (H+), in the absence of deterioration of renal function, and it is accompanied by hyperchloremic metabolic acidosis with normal anion gap. The symptoms can be growth retardation, vomiting, constipation, lack of appetite, polydipsia and polyuria, nephrocalcinosis, weakness and even muscle paralysis due to hypokalemia. It is often accompanied by sensorineural hearing impairment. Correcting acidosis can have a variety of benefits such as restoring normal growth, decreasing hypokalemia, stabilizing or preventing nephrocalcinosis and decreasing the risk of osteopenia. Timely diagnosis and adequate treatment of patients make them remain asymptomatic and able to lead a good quality of life. We present the cases of two siblings affected by distal renal tubular acidosis, its diagnostic process, treatment and current follow-up.

Acidosis tubular renal como presentación clínica de Síndrome de Sjögren: reporte de caso / Renal tubular acidosis as a clinical presentation of Sjögren Syndrome: case report

Presentamos el caso clínico de una mujer en la quinta década de la vida, de nacionalidad argentina, que acudió a la guardia de clínica médica de un hospital de tercer nivel por cuadro de mialgias y paresia en las cuatro extremidades, de inicio agudo, progresivo, con dificultad para la movilización de miembros superiores, bipedestación y marcha. Se constató hipocalemia severa, acidosis metabólica, pH urinario alcalino, brecha aniónica urinaria positiva (excreción de amonio), hipocitraturia e hipercalciuria, por lo que se diagnosticó Acidosis Tubular Renal (ATR) tipo I; además se evidenció elevación de creatinkinasa (CK) e insuficiencia renal aguda que corrigió con la reposición de líquidos. Al interrogatorio dirigido, la paciente refirió síndrome seco asociado a artralgias, de varios años de evolución, por lo que se realizaron estudios complementarios que apoyaron el diagnóstico de Síndrome de Sjögren.

We present the clinical case of a woman in the fifth decade of life, argentina, who went to the Internal Medicine emergency room of a third level hospital for symptoms of myalgia and paresis in all four extremities, acute onset, progressive, with difficulty for the mobilization of members superior, standing and walking. Severe hypokalemia, metabolic acidosis, alkaline urinary pH, positive urinary anion GAP (ammonium excretion), hypocitraturia and hypercalciuria were diagnosed. Renal Tubular Acidosis (RTA) type I was diagnosed; acute renal failure was also noted, which corrected with the treatment and elevated creatine kinase (CK). In the anamnesis, the patient reported dry syndrome associated with arthralgias of years of evolution, so that complementary studies were carried out that supported the diagnosis of Sjögren's Syndrome (SS).

Acetazolamide-Induced Type II Renal Tubular Acidosis and Muscle Weakness

No abstract available.

Proximal renal tubular acidosis with and without Fanconi syndrome

Proximal renal tubular acidosis (RTA) is caused by a defect in bicarbonate (HCO₃⁻) reabsorption in the kidney proximal convoluted tubule. It usually manifests as normal anion-gap metabolic acidosis due to HCO₃⁻ wastage. In a normal kidney, the thick ascending limb of Henle’s loop and more distal nephron segments reclaim all of the HCO₃⁻ not absorbed by the proximal tubule. Bicarbonate wastage seen in type II RTA indicates that the proximal tubular defect is severe enough to overwhelm the capacity for HCO₃⁻ reabsorption beyond the proximal tubule. Proximal RTA can occur as an isolated syndrome or with other impairments in proximal tubular functions under the spectrum of Fanconi syndrome. Fanconi syndrome, which is characterized by a defect in proximal tubular reabsorption of glucose, amino acids, uric acid, phosphate, and HCO₃⁻, can occur due to inherited or acquired causes. Primary inherited Fanconi syndrome is caused by a mutation in the sodium-phosphate cotransporter (NaPₐ-II) in the proximal tubule. Recent studies have identified new causes of Fanconi syndrome due to mutations in the EHHADH and the HNF4A genes. Fanconi syndrome can also be one of many manifestations of various inherited systemic diseases, such as cystinosis. Many of the acquired causes of Fanconi syndrome with or without proximal RTA are drug-induced, with the list of causative agents increasing as newer drugs are introduced for clinical use, mainly in the oncology field.

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.

Adult Idiopathic Renal Fanconi Syndrome: A Case Report

Renal Fanconi syndrome (RFS) is caused by generalized proximal tubular dysfunction and can be divided into hereditary and acquired form. Adult-onset RFS is usually associated with drug toxicity or systemic disorders, and modern molecular genetics may explain the etiology of previous idiopathic cases of RFS. Here, we report the case of a 52-year-old woman with RFS whose etiology could not be identified. She presented with features of phosphaturia, renal glucosuria, aminoaciduria, tubular proteinuria, and proximal renal tubular acidosis. Her family history was unremarkable, and previous medications were nonspecific. Her bone mineral density was compatible with osteoporosis, serum intact parathyroid hormone level was mildly elevated, and 25(OH) vitamin D level was insufficient. Her blood urea nitrogen and serum creatinine levels were 8.4 and 1.19 mg/dL, respectively (estimated glomerular filtration rate, 53 mL/min/1.73 m²). Percutaneous renal biopsy was performed but revealed no specific renal pathology, including mitochondrial morphology. No mutation was detected in EHHADH gene. We propose the possibility of involvement of other genes or molecules in this case of adult RFS.

Primary Autosomal Recessive Distal Renal Tubular Acidosis Caused by a Common Homozygous SLC4A1 Mutation in Two Lao Families

Primary distal renal tubular acidosis (dRTA) caused by mutations of the SLC4A1 gene, which encodes for erythroid and kidney isoforms of anion exchanger, shows marked difference in inheritance patterns and clinical features in different parts of the world. While the disease shows autosomal dominant inheritance without any red cell morphological abnormalities in the temperate countries, it is almost invariably recessive, and often accompanies red cell morphological abnormalities or hemolytic anemia in the tropics, especially in Southeast Asia. Here, we report three patients with autosomal recessive (AR) dRTA, presenting with typical findings of failure to thrive and rickets, from two unrelated Lao families. The mutational analyses revealed that all three patients harbored the same homozygous SLC4A1 mutation, p.Gly701Asp. Adequate supplementation of alkali and potassium resulted in remarkable improvement of growth retardation and skeletal deformities of the patients. This is the first case report of Lao patients with AR dRTA caused by SLC4A1 mutations.

Normal anion gap metabolic acidosis secondary to topiramate intake: case report

ABSTRACT Introduction: Topiramate is a drug used to treat various types of epilepsy and as prophylaxis in cases of migrainous headache. One of its mechanisms of action is the inhibition of carbonic anhydrase in the kidney that triggers the excretion of alkaline urine resulting in metabolic acidosis. Case presentation: 17-year-old female patient from Mexico City who regularly uses topiramate, quetiapine and sertraline for the management of depressive disorder. She developed normal anion gap metabolic acidosis secondary to topiramate intake. As a result, she required invasive ventilatory support due to reduced consciousness and respiratory distress. Adequate response to management with laxatives and bicarbonate was achieved, with full renal and neurological recovery. Discussion: Metabolic acidosis is the most common acid-base disorder observed in clinical practice. The difference between measurable cations and anions, known as anion gap, helps to classify the severity of acidosis. Bicarbonate losses or renal tubular disorders generate normal anion gap acidosis as opposed to acidosis resulting from an overproduction of endogenous acid or renal failure, which causes high anion gap. Topiramate is a little known cause of normal anion gap metabolic acidosis; by inhibiting carbonic anhydrase, it causes mixed renal tubular acidosis or type 3 acidosis, as a consequence of the inability to secrete hydrogen ions in the collecting tubule, and a limitation of bicarbonate reabsorption in the proximal tubule. Conclusion: Topiramate, either in therapeutic doses or in overdose, can lead to normal anion gap metabolic acidosis due to the inhibition of carbonic anhydrase in the kidneys. It is usually reversible after starting bicarbonate.

RESUMEN Introducción. El topiramato es un medicamento que se usa en el tratamiento de varios tipos de epilepsia y como profilaxis en casos de cefalea migrañosa. Entre sus mecanismos de acción, la inhibición de la anhidrasa carbónica en el riñón desencadena la excreción de orina alcalina ocasionando acidosis metabólica. Presentación del caso. Paciente femenino de 17 años procedente de la Ciudad de México con antecedente de consumo de topiramato, quetiapina y sertralina para manejo de síndrome depresivo, quien desarrolla acidosis metabólica de anión restante normal secundaria a ingesta de topiramato. La joven requiere soporte ventilatorio invasivo por deterioro del estado de conciencia y síndrome de dificultad respiratoria y presenta adecuada respuesta a manejo con catártico y bicarbonato sin compromiso renal y sin secuelas neurológicas. Discusión. La acidosis metabólica es la alteración ácido base más frecuente en la práctica clínica. La diferencia entre cationes y aniones medibles, conocida como anión restante o brecha aniónica, permite clasificar este tipo de acidosis. Las pérdidas de bicarbonato o trastornos de la función tubular renal generan acidosis de anión restante normal; por el contrario, la acidosis causada por sobreproducción de ácido endógeno o por insuficiencia renal genera anión restante elevado. El topiramato es una causa poco conocida de acidosis metabólica con anión restante normal; al inhibir la anhidrasa carbónica, se ocasiona una acidosis tubular renal mixta o tipo 3 debido a una in capacidad de secreción de hidrogeniones en el túbulo colector y una limitación en la reabsorción del bicarbonato en el túbulo proximal. Conclusión. El topiramato en dosis terapéutica o en sobredosis puede generar acidosis metabólica de anión restante normal debido a la inhibición de la anhidrasa carbónica a nivel renal. Se trata de un cuadro reversible en el cual el manejo con bicarbonato ha mostrado buenos resultados clínicos.

Clinical features of hereditary distal renal tubular acidosis and SLC4A1 gene mutation / 中国当代儿科杂志

<p><b>OBJECTIVE</b>To study the clinical features of two families with distal renal tubular acidosis (dRTA) and mutations in the pathogenic gene SLC4A1.</p><p><b>METHODS</b>Family investigation, medical history collection, and measurement of biochemical parameters were performed to analyze the clinical phenotype and genetic characteristics of dRTA. Direct sequencing was used to detect SLC4A1 gene mutations.</p><p><b>RESULTS</b>Three patients in these two families (two of them were mother and son) were diagnosed with dRTA with typical clinical features, including short stature, metabolic acidosis, alkaline urine, hypokalemia, and nephrocalcinosis. SLC4A1 gene analysis showed that all the three patients had a pathogenic missense mutation R589H (c.1766G>A). The child in family 1 had a de novo mutation of SLC4A1, and the child in family 2 had an SLC4A1 gene mutation inherited from the mother, which met the characteristic of autosomal dominant inheritance.</p><p><b>CONCLUSIONS</b>This study reports the R589H mutation in SLC4A1 gene in families with hereditary dRTA for the first time in China. Clinical physicians should perform gene detection for patients suspected of hereditary dRTA to improve the diagnosis and treatment of this disease.</p>

Renal Tubular Acidosis in Patients with Primary Sjögren's Syndrome

Primary Sjögren's syndrome (pSS) is characterized by lymphocytic infiltration of the exocrine glands resulting in decreased saliva and tear production. It uncommonly involves the kidneys in various forms, including tubulointerstitial nephritis, renal tubular acidosis, Fanconi syndrome, and rarely glomerulonephritis. Its clinical symptoms include muscle weakness, periodic paralysis, and bone pain due to metabolic acidosis and electrolyte imbalance. Herein, we describe the cases of two women with pSS whose presenting symptoms involve the kidneys. They had hypokalemia and normal anion gap metabolic acidosis due to distal renal tubular acidosis and positive anti-SS-A and anti-SS-B autoantibodies. Since one of them experienced femoral fracture due to osteomalacia secondary to renal tubular acidosis, an earlier diagnosis of pSS is important in preventing serious complications.

The role of renal proximal tubule transport in the regulation of blood pressure

The electrogenic sodium/bicarbonate cotransporter 1 (NBCe1) on the basolateral side of the renal proximal tubule plays a pivotal role in systemic acid-base homeostasis. Mutations in the gene encoding NBCe1 cause severe proximal renal tubular acidosis accompanied by other extrarenal symptoms. The proximal tubule reabsorbs most of the sodium filtered in the glomerulus, contributing to the regulation of plasma volume and blood pressure. NBCe1 and other sodium transporters in the proximal tubule are regulated by hormones, such as angiotensin II and insulin. Angiotensin II is probably the most important stimulator of sodium reabsorption. Proximal tubule AT(1A) receptor is crucial for the systemic pressor effect of angiotensin II. In rodents and rabbits, the effect on proximal tubule NBCe1 is biphasic; at low concentration, angiotensin II stimulates NBCe1 via PKC/cAMP/ERK, whereas at high concentration, it inhibits NBCe1 via NO/cGMP/cGKII. In contrast, in human proximal tubule, angiotensin II has a dose-dependent monophasic stimulatory effect via NO/cGMP/ERK. Insulin stimulates the proximal tubule sodium transport, which is IRS2-dependent. We found that in insulin resistance and overt diabetic nephropathy, stimulatory effect of insulin on proximal tubule transport was preserved. Our results suggest that the preserved stimulation of the proximal tubule enhances sodium reabsorption, contributing to the pathogenesis of hypertension with metabolic syndrome. We describe recent findings regarding the role of proximal tubule transport in the regulation of blood pressure, focusing on the effects of angiotensin II and insulin.

Two Cases of Distal Renal Tubular Acidosis accompanied by Sjogren's Syndrome / 대한내과학회지

Renal tubular acidosis (RTA) is a syndrome characterized by hyperchloremic metabolic acidosis and an inability to excrete highly acid urine, in which the impaired acid excretion is disproportional to the reduction in the glomerular filtration rate. Distal renal tubular acidosis (dRTA) is frequently associated with immune-mediated disease, including Sjogren's syndrome. Sjogren's syndrome is a systemic autoimmune disease that mainly affects exocrine glands, such as the lacrimal and salivary glands, resulting in xerophthalmia and xerostomia. Extraglandular manifestations are frequent and may include renal involvement. Recently, we experienced two cases of renal tubular acidosis in patients with Sjogren's syndrome. The first patient had lower extremity weakness and hypokalemia and the second had nephrocalcinosis. We discuss the frequency and pathogenesis of dRTA in Sjogren's syndrome.