Type 4 renal tubular acidosis in a patient with lupus nephritis.

Although renal tubular acidosis (RTA) is a rare complication of systemic lupus erythematosus (SLE), type 4 RTA associated with lupus nephritis is extremely rare. A 20-year-old woman presented with malaise and edema in the lower extremities and face. She had multiple lymphadenopathies. There were 20% eosinophil in blood smear and 32% in bone marrow aspiration. Serology revealed positive antinuclear antibody at 1:1000 titer, positive double-stranded DNA antibodies, and low complements C3 and C4 levels. Urinary sediment was active and urinary protein excretion was 4.8 g/d. The SLE Disease Activity Index score was 23. A high SLE Disease Activity Index scores was proposed as a potential risk factor for type 4 RTA. Type 4 RTA may complicate SLE, and specifically, patients with high SLEDAI scores and lymphadenopathy may pose a high risk. Our patient responded successfully to immunomodulatory therapy.

[Inherited tubular renal acidosis]. / Acidose tubulaire rénale héréditaire.

Renal tubular acidosis (RTA) is a tubulopathy characterized by metabolic acidosis with normal anion gap secondary to abnormalities of renal acidification. RTA can be classified into four main subtypes: distal RTA, proximal RTA, combined proximal and distal RTA, and hyperkalemic RTA. Distal RTA (type 1) is caused by the defect of H(+) secretion in the distal tubules and is characterized by the inability to acidify the urine below pH 5.5 during systemic acidemia. Proximal RTA (type 2) is caused by an impairment of bicarbonate reabsorption in the proximal tubules and characterized by a decreased renal bicarbonate threshold. Combined proximal and distal RTA (type 3) secondary to a reduction in tubular reclamation of bicarbonate and an inability to acidify the urine in the face of severe acidemia. Hyperkalemic RTA (type 4) may occur as a result of aldosterone deficiency or tubular insensitivity to aldosterone. Clinicians should be alert to the presence of RTA in patients with an unexplained normal anion gap acidosis, hypokalemia, recurrent nephrolithiasis and nephrocalcinosis. The mainstay of treatment of RTA remains alkali replacement.

Evaluation of renal tubular acidosis.

Renal tubular acidoses (RTA) comprises of a group of disorders characterized by a low capacity for net acid excretion and persistent hyperchloremic, metabolic acidosis. The RTAs are classified into chiefly three types (types 1,2 and 4) based on clinical and laboratory characteristics. Correct diagnosis involves careful evaluation, including exclusion of other entities causing acidosis. A variety of tests are required to be administered in a stepwise fashion for the diagnosis and characterization of RTA.

Renal tubular acidosis.

Renal tubular acidosis (RTA) is a form of metabolic acidosis due to abnormal alkali (bicarbonate) loss by the kidneys or their failure to excrete net acid. While the latter does occur in chronic renal failure, the term RTA is usually applied only when the glomerular filtration rate is normal or near normal. As well as a cause of metabolic acidosis, RTA often presents as renal stone disease with nephrocalcinosis, rickets/osteomalacia, and growth retardation in children. In this brief review, we have summarized the classification, clinical features and the underlying cell and molecular pathophysiology of RTA. However, despite significant advances in our understanding of the mechanisms of RTA, its treatment is still empirical and based largely on alkali replacement therapy; but its wider significance in renal stone and bone disease is becoming increasingly recognized.

Renal tubular acidosis: developments in our understanding of the molecular basis.

Renal tubular acidosis is a metabolic acidosis due to impaired acid excretion by the kidney. Hyperchloraemic acidosis with a normal anion gap and normal (or near normal) glomerular filtration rate, and in the absence of diarrhoea, defines this disorder. However, systemic acidosis is not always evident and renal tubular acidosis can present with hypokalaemia, medullary nephrocalcinosis and recurrent calcium phosphate stone disease, as well as growth retardation and rickets in children, or short stature and osteomalacia in adults. Renal dysfunction in renal tubular acidosis is not always confined to acid excretion and can be part of a more generalised renal tubule defect, as in the renal Fanconi syndrome. Isolated renal tubular acidosis is more usually acquired, due to drugs, autoimmune disease, post-obstructive uropathy or any cause of medullary nephrocalcinosis. Less commonly, it is inherited and may be associated with deafness, osteopetrosis or ocular abnormalities. The clinical classification of renal tubular acidosis has been correlated with our current physiological model of how the nephron excretes acid, and this has facilitated genetic studies that have identified mutations in several genes encoding acid and base ion transporters. In vitro functional studies of these mutant proteins in cell expression systems have helped to elucidate the molecular mechanisms underlying renal tubular acidosis, which ultimately may lead to new therapeutic options in what is still treatment only by giving an oral alkali.

Nefrocalcinosis: ¿camino a la insuficiencia renal? / Nephrocalcinosis: a way to renal insuficiency?

Nefrocalcinosis es un término que significa depósito de calcio, oxalato y fosfatos en el interior del túbulo renal y en el intersticio. Múltiples patologias son causantes potenciales de este, proceso aunque a festos prdcticos pocas de ellos la produzcan (AU)

[Distal renal tubular acidosis with rhabdomyolysis as the presenting form in 4 pregnant women]. / Acidosis tubular renal distal con rabdomiolisis como forma de presentación en 4 mujeres embarazadas.

We describe four pregnant patients with distal renal tubular acidosis (type I) (DRTA) whose initial presentation was rhabdomyolysis (RML) secondary to severe hypokalemia. We draw attention to the unusual presentation of DRTA during pregnancy, the low frequency of DRTA in adult patients and RML as initial manifestation. In one case the DRTA was secondary to Sjögren Syndrome and the etiology was unknown in the rest of the cases. We discuss the potential pathogenic mechanisms to explain hypokalemic RML and the various causes of DRTA in adult patients.

[Type 4 renal tubular acidosis caused by spironolactone. A case report]. / Acidosi tubulare renale tipo 4 da spironolattone. Caso clinico.

The authors describe a case of type 4 renal tubular acidosis, observed in a subject with liver cirrhosis, the pathogenetic cause of which was probably the assumption of spironolactone. It is thought that, even if such an eventuality is not very frequent, it must be considered in clinical practice, in view of the negative consequences that the reduction in urinary ammonium excretion and hyponatriemia, together with this particular form of acidosis, may have on the neurological state of the patients.

A new classification for renal defects in net acid excretion.

The traditional classification of the group of disorders called renal tubular acidosis (RTA) into proximal and distal subclasses is based on which nephron segment is thought to have an abnormal function. Nevertheless, such a distinction may not be correct and also does not characterize the pathophysiology of the renal acidosis in each patient. In this article, we propose an alternative classification, one that is based on the component of net acid excretion that is abnormal. We also suggest expanding the definition of net acid excretion to include a term that describes the renal handling of metabolizable organic anions because their loss in the urine represents the loss of "potential bicarbonate." Because a low rate of excretion of ammonium (NH4+) is present in patients with both distal and isolated proximal RTA, our initial clinical step in patients with hyperchloremic metabolic acidosis (HCMA) is to evaluate the rate of excretion of NH4+. The basis for a low rate of excretion of NH4+ is shown by examining the urine pH. If the urine pH is low, further studies are performed to determine why the availability of NH3 is low; if the urine pH is high, further investigations are initiated to examine if the defect in H+ secretion involves the proximal or the distal nephron. Conversely, if the rate of excretion of NH4+ is high in a patient with HCMA, a component of the degree of acidosis could be attributable to a high rate of excretion of metabolizable organic anions. Case examples are provided to illustrate the approach and its implications for future molecular studies.

[Renal tubular acidosis (RTA)].

Renal tubular acidosis (RTA) is applied to a group of transport defects involving the reabsorption of bicarbonate (proximal RTA or type II), the excretion of hydrogen ion (distal RTA or type I), or both (type III). Aldosteron deficiency and resistant state to aldosteron form hyperkalemic RTA which is called type IV RTA. A large number of etiologies of RTA have been identified. Almost all RTA in childhood are congenital. In contrast, almost all RTA in adulthood are secondary. Two renal complications such as low molecular weight proteinuria and renal cyst formation have recently been described in distal RTA. Molecular defects of RTA will be identified in the near future.