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INTRODUCTION: Hereditary transthyretin amyloidosis (ATTRv) is a severe autosomal dominant systemic disease. It affects the peripheral and autonomic nervous systems, heart, kidneys, and eyes. Amyloid deposition has been demonstrated in the glomerular and tubulointerstitial compartments of the kidney. Therefore, urinary acidification disorders such as renal tubular acidosis (RTA) may be early manifestations of renal involvement in this population. OBJECTIVE: To evaluate the prevalence of RTA in individuals with ATTRv. METHODS: We included symptomatic and asymptomatic individuals with TTR mutation, older than 18 years, GFR >45 mL/min/1.73m2, without systemic metabolic acidosis. Urinary acidification protocol was performed with furosemide and fludrocortisone after 12 h of water deprivation (water deprivation test - WDT) and measurements of urine ammonium ( UNH 4 + ) and titratable acidity (UTA). Proximal RTA (pRTA) was diagnosed when FEHCO3>10%. Incomplete form distal RTA (dRTA) was diagnosed if UpH>5.3. RESULTS: We selected 49 individuals with a mean age of 40 (35.5-56.5) years, 63% of which were female, 84% were Caucasian, and mean GFR was 85.5 ± 20.5 mL/min/1.73m2. 94% had the genetic variant Val50Met and 57% were symptomatic. The prevalence of pRTA was 2% and of dRTA was 16.3%. In the subgroup with dRTA, there was no significant increase in excretion of UNH 4 + and UTA. We observed a good correlation between UpH by potentiometry and UpH dipstick. A UpH<5.5 on the dipstick had 100% sensitivity and negative predictive value to exclude dRTA. CONCLUSION: A high prevalence of RTA was found in individuals with TTR mutations. The UpH dipstick after WDT had good accuracy for screening for dRTA. Further studies are needed to evaluate the impact of early diagnosis and treatment of RTA in this population.

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BACKGROUND Distal renal tubular acidosis (dRTA) is a defect in the urinary acidification process that limits the elimination of protons [H+] by alpha intercalated cells in the collecting tubules, with consequent metabolic acidosis with a normal plasma anion gap. The relationship between this tubulopathy and immune-mediated diseases like Sjögren syndrome, rheumatoid arthritis, autoimmune hepatitis, primary biliary cirrhosis, systemic lupus erythematosus, and thyroiditis is well known. Further, the pathophysiological mechanisms are diverse, but, unfortunately, many are not yet fully understood. We report 3 cases of dRTA in patients with different autoimmune diseases and review the pathophysiological mechanisms already described. CASE REPORT The first case involved a 29-year-old woman with autoimmune hepatitis. She had metabolic acidosis with persistent hypokalemia, and a kidney stone was also identified. The second case involved a 67-year-old woman diagnosed with rheumatoid arthritis. She had metabolic acidosis with hypokalemia. The third case involved a 30-year-old woman with Sjögren syndrome and persistent metabolic acidosis. In addition to the presence of metabolic acidosis with a normal plasma anion gap, all 3 patients exhibited urine with a supraphysiologic pH (above 5.3). CONCLUSIONS Autoimmune diseases may be associated with deficits in urinary acidification with consequent metabolic acidosis and, therefore, systemic repercussions. This association must be remembered and researched because correct diagnosis and treatment will serve to reduce complications.

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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.

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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.

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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.

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Primary Sjögren's syndrome is a systemic and chronic autoimmune disease. Renal involvement may occur in up to 30% of patients. The incidence of tubulopathies ranges from 2.6 to 33%. They are manifested by defects in the urine concentration and hydroelectrolyte alterations, mainly distal tubular acidosis and exceptionally proximal tubular acidosis. These disorders can be associated with nephrocalcinosis and renal lithiasis. We report the case of a patient with primary Sjögren who presented proximal renal tubular acidosis associated with recurrent renal colic due to renal lithiasis and nephrocalcinosis. We highlight the importance of diagnosing renal tubular acidosis in patients with Sjögren's syndrome that present alterations in urinary sediment and electrolyte disorders to avoid nephrocalcinosis and nephrolithiasis. Acidosis correction treatment aims to prevent the progression of the disorder and preserve renal function.

El síndrome de Sjögren primario es una enfermedad autoinmune sistémica de evolución crónica. Puede presentar compromiso renal hasta en un 30% de los pacientes.La incidencia de tubulopatías varía de 2.6 a 33%. Se manifiestan por defectos en la concentración de la orina y alteraciones hidroelectrolíticas, principalmente acidosis tubular distal y de manera excepcional acidosis tubular proximal. Estos trastornos pueden asociarse a Nefrocalcinosis y litiasis renal. Reportamos el caso de una paciente con Sjögren primario que presentó acidosis tubular renal proximal asociada a cólicos renales recurrentes por litiasis renal y nefrocalcinosis. Destacamos la importancia de diagnosticar acidosis tubular renal en pacientes con síndrome de Sjögren que presenten alteraciones en el sedimento urinario y desórdenes electrolíticos para evitar la nefrocalcinosis medular y las nefrolitiasis asociadas. La terapia para la corrección de la acidosis tiene como objetivo evitar la progresión del trastorno y preservar la función renal.

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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.

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Background: Hypokalemic periodic paralysis (HypoKPP) is characterized by transient episodes of flaccid muscle weakness. We describe the case of a teenaged boy with HypoKPP and hyperthyroidism due to Hashimoto's thyroiditis with initial manifestation of renal tubular acidosis. This combination is rare and little described previously in men. Case presentation: A 17-year-old boy was admitted after three days of muscular weakness and paresthesia in the lower limbs with an ascending evolution, leading to prostration. Decreased strength was found in the lower limbs without a defined sensory level, reduced patellar and ankle reflexes. Positive antithyroid antibodies were found. He received hydration treatment, IV potassium and levothyroxine, with which there was a clinical improvement. Other examinations led to the diagnosis of type 1 renal tubular acidosis. Conclusion: HypoKPP is a rare disorder characterized by acute episodes of muscle weakness. Type 1 renal tubular acidosis can occur as a consequence of thyroiditis, which is explained by the loss of potassium. This combination is unusually rare, and has not been described before in men. The etiopathogenesis of the disease as well as a dynamic explanation of what happened with the patient are discussed in this report.

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Hypokalemic periodic paralysis (hypoKPP) is a clinical entity characterized by recurrent skeletal muscle paralysis due to a decrease in serum potassium levels; hypoKPP can have either a primary (familial) or a secondary cause. One of the secondary causes of hypoKPP is distal renal tubular acidosis (dRTA). Distal renal tubular acidosis (dRTA) is diagnosed when the urinary pH is greater than 5.3 and in the presence of hyperchloremic metabolic acidosis and hypokalemia, with one of the causes being primary Sjögren's syndrome (pSS). PSS can have both glandular and extra glandular manifestations, with dryness of the eyes and mouth being the most common presenting symptoms. DRTA arising from pSS is very unusual, occurring in fewer than 2% of the cases of Sjogren's syndrome (SS). Here, we report on a case of recurrent flaccid quadriparesis that appears to have been caused by distal RTA, resulting in hypokalemia; upon further investigation and clinical evaluation, the patient was diagnosed with pSS.

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Renal tubular acidosis is a disease prevalent in childhood, responsible for a decrease in growth due inadequate acid-base levels regulation. It is well known that systemic conditions can generate or accompany nail changes by different pathophysiologic mechanisms, however no one has ever found or reported any association of onychopathy with renal tubular acidosis so far. That is why we would like to share our experience on this topic.

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