We report an unusual case of 5-yrs-old girl presenting with recurrent episodic weakness with documented hypokalemia, polyuria and failure to thrive. The child was finally diagnosed as having distal renal tubular acidosis. Imaging studies revealed associated hypoechoic spaces in renal medulla. Long term treatment with alkali and maintenance of normokalemia lead to regression of these morphological changes.

Background:

primary distal renal tubular acidosis in children (RTA) is characterized by metabolic acidosis due to defect in urinary excretion of hydrogen (H+) in the distal tubular. aim: To report the epidemiological, clinical, therapeutic and evolutionary of distal RTA in our patients. Patients and methods: We conducted a retrospective study of all cases of distal RTA collected in the department of pediatrics of Hedi Chaker University hospital in the south of Tunisia, during a period of 23 years (1988-2010). We studied the epidemiological, clinical, biological, evolutionary and therapeutic data. results: During the study period 15 cases of distal RTA were collected. The average age was 6 months (1 month -2 years). Most common presenting symptoms were vomiting (8cases), failure to thrive (4cases), lack of appetite, polyuria-polydipsia syndrome (1case) and urinary infection (2cases). The clinical examination showed staturoponderal delay (9 cases), dehydration (6 cases), signs of rickets (3 cases) and polyuria (10 cases). Biological data showed high urine pH in the presence of metabolic acidosis in 11 cases, hypokalaemia in 10 cases and hypercalciuria in all cases. Urine acidification test with ammonium chloride was performed in 4 cases, the urinary pH was always higher than 5.5 in all cases. Ammoniuria performed in 9 cases was less than 40mmol/l. Radiological investigation objectified a nephrocalcinosis in fourteen patients and signs of rickets in three cases. Deafness was found in three patients. Genetic study performed in two cases showed mutation of ATP6V1B1 gene. The medical treatment involved an alkali load. Long-term outcome was favorable in 7 cases.

Conclusion:

The distal renal tubular acidosis is a rare pathology in our country but probably under diagnosed. The clinical gravity of this disease and the risk of evolution towards the terminal renal insufficiency justify an antenatal diagnosis to establish a neonatal management or propose a therapeutic interruption of the pregnancy if the distal RTA is associated with a severe pathology.

Renal tubular acidosis is a group of disorders in which there is metabolic acidosis due to defect in renal tubular acidification mechanism to maintain normal plasma bicarbonate and blood pH. Irrespective of organ system involved, oral cavity often reflects the disease occurring anywhere in the body. Thus congenital chronic renal diseases, causing acid-base disturbances affects development and structure of the teeth. Chronic renal tubular acidosis causes enamel defects, dental caries, oral candidiasis, angular cheilitis, etc. We hereby present an unusual case report of a 4-year-old boy suffering from renal tubular acidosis associated with rampant caries, whose full mouth rehabilitation has been done.

A multi-domain, multi-functional, 230kDa extracellular matrix (ECM) protein, hensin, regulates the adaptation of rabbit kidney to metabolic acidosis by remodeling collecting duct intercalated cells. Conditional deletion of hensin in intercalated cells of the mouse kidney leads to distal renal tubular acidosis and to a significant reduction in the number of cells expressing the basolateral chloride-bicarbonate exchanger, kAE1, a characteristic marker of α-intercalated cells. Although hensin is secreted as a monomer, its polymerization and ECM assembly are essential for its role in the adaptation of the kidney to metabolic acidosis. Galectin-3, a unique lectin with specific affinity for β-galactoside glycoconjugates, directly interacts with hensin. Acidotic rabbits had a significant increase in the number of cells expressing galectin-3 in the collecting duct and exhibited co-localization of galectin-3 with hensin in the ECM of microdissected tubules. In this study, we confirmed the increased expression of galectin-3 in acidotic rabbit kidneys using real-time RT-PCR. Galectin-3 interacted with hensin in vitro via its carbohydrate binding C-terminal domain, and the interaction was competitively inhibited by lactose, removal of the C-terminal domain of galectin-3, and deglycosylation of hensin. Galectin-9 partially oligomerized hensin in vitro. Our results demonstrate that galectin-3 plays a critical role in hensin ECM assembly by oligomerizing secreted monomeric hensin. Both the N-terminal and C-terminal domains are required for this function. We suggest that in the case of galectin-3 null mice, galectin-9 may partially substitute for the function of galectin-3.

Hereditary hypouricemia is a rare disorder characterized by extremely low serum uric acid levels caused by excessive urinary excretion due to an inherited tubular defect in urate handling. Exercise-induced acute kidney injury (AKI) is the main complication of this disorder, though AKI may also be induced by other factors. A 7-month-old boy with hereditary hypouricemia developed AKI associated with severe dehydration caused by rotavirus gastroenteritis. He also showed severe hypernatremia and metabolic acidosis and received continuous renal replacement therapy for 3 days. He showed no signs of hydronephrosis or urolithiasis. However, hypouricemia was noted when his renal function recovered (serum uric acid <0.6 mg/dl). Analysis of the urate transporter 1 gene revealed a homozygous nonsense mutation in exon 4 (c.774G > A, p.W258X). Both parents were heterozygous for the mutation and his younger brother was later determined to have severe hypouricemia (0.6 mg/dl).

Conclusion:

Uric acid is an essential factor for scavenging oxidative stressors. In this patient, severe dehydration may have directly caused pre-renal AKI, but susceptibility to oxidative stressors under severe dehydration, as well as exercise, may also contribute to AKI. Careful attention should be paid to dehydration, especially in young children, to avoid the development of AKI in patients with hereditary hypouricemia.

Carbonic anhydrase-II deficiency is an autosomal recessive disorder with a triad of cerebral calcification, osteopetrosis and renal tubular acidosis (often combined proximal and distal). Mental retardation, growth failure, complications of osteopetrosis and other features were all recorded in this syndrome. We present a case of an Iraqi male with all these features and a positive family history.

Distal renal tubular acidosis (dRTA) or RTA type I is characterised by reduced H+&nbsp;hydrogen ions and ammonium urinary excretion. In children affected by dRTA there is stunted growth, vomiting, constipation, loss of appetite, polydipsia and polyuria, nephrocalcinosis, weakness and muscle paralysis due to hypokalaemia. This work summarises progress made in dRTA genetic studies in populations studied so far. DRTA is heterogeneous and as such, transporters and ion channels are analysed which have been identified in alpha-intercalated cells of the collecting duct, which could explain cases of dRTA not associated with the hitherto studied genes. DRTA can be autosomal dominant or autosomal recessive. Autosomal recessive dRTA appears in the first months of life and progresses with nephrocalcinosis and early or late hearing loss. Autosomal dominant dRTA is less severe and appears during adolescence or adulthood and may or may not develop nephrocalcinosis. In alpha-intercalated cells of the collecting duct, the acid load is deposited into the urine as titratable acids (phosphates) and ammonium. Autosomal recessive dRTA is associated with mutations in genes ATP6V1B1, ATP6V0A4&nbsp;and&nbsp;SLC4A1, which encode subunits a4 and B1 of V-ATPase and the AE1 bicarbonate/chloride exchanger respectively. By contrast, autosomal dominant dRTA is only related to mutations in AE1.

Mutations in SLC4A4, the gene encoding the electrogenic Na(+)-HCO3(-) cotransporter NBCe1 cause severe proximal renal tubular acidosis (pRTA), growth retardation, decreased IQ, eye and teeth abnormalities. Among the known NBCe1 mutations, the disease causing mechanism of the T485S (NBCe1-A numbering) mutation is intriguing because the substituted amino acid, serine, is structurally and chemically similar to threonine. In this study, we performed intracellular pH and whole cell patch-clamp measurements to investigate the base transport and electrogenic properties of NBCe1-A-T485S in mammalian HEK 293 cells. Our results demonstrated that Ser substitution of Thr485 decreased base transport by ~50%, and importantly, converted NBCe1-A from an electrogenic to an electroneutral transporter. Aqueous accessibility analysis using sulfhydryl reactive reagents indicated that Thr485 likely resides in an NBCe1-A ion interaction site. This critical location is also supported by the finding that G486R (a pRTA causing mutation) alters the position of Thr485 in NBCe1-A thereby impairing its transport function. By using NO3(-) as a surrogate ion for CO3(2-), our result indicated that NBCe1-A mediates electrogenic Na(+)-CO3(2-) cotransport when functioning with a 1:2 charge transport stoichiometry. In contrast, electroneutral NBCe1-T485S is unable to transport NO3(-) compatible with the hypothesis that it mediates Na(+)-HCO3(-) cotransport. In patients, NBCe1-A-T485S is predicted to transport Na(+)-HCO3(-) in the reverse direction from blood into proximal tubule cells thereby impairing transepithelial HCO3(-) absorption, possibly representing a new pathogenic mechanism for generating human pRTA.

Establishment of a preferential liver allocation rule for simultaneous liver and kidney transplantation (SLK) and revisions of laws regarding organ transplants from deceased donors have paved the way for SLK in Japan. Very few cases of SLK have been attempted in Japan, and no such recipients have survived for longer than 40 days. The present report describes a case of a 50-year-old woman who had undergone living donor liver transplantation at the age of 38 years for management of post-partum liver failure. After the first transplant surgery, she developed hepatic vein stenosis and severe hypersplenism requiring splenectomy. She was then initiated on hemodialysis (HD) due to the deterioration of renal function after insertion of a hepatic vein stent. She was listed as a candidate for SLK in 2011 because she required frequent plasma exchange for hepatic coma. When her Model for End-stage Liver Disease score reached 46, the new liver was donated 46 days after registration. The reduced trisegment liver and the kidney grafts were simultaneously transplanted under veno-venous bypass and intraoperative HD. The hepatic artery was reconstructed prior to portal reconstruction in order to shorten anhepatic time. Although she developed subcapsular bleeding caused by hepatic contusion on the next day, subsequent hemostasis was obtained by transcatheter embolization. Thereafter, her recovery was uneventful, except for mild rejection and renal tubular acidosis of the kidney graft. This case highlights the need to establish Japanese criteria for SLK.

Chronic acidosis is an important, often overlooked cause of growth retardation. Here we present the case of a girl with distal renal tubular acidosis who had visited multiple hospitals before the diagnosis was made. She presented to us in adolescence with non anion gap metabolic acidosis, hypokalemia, severe growth retardation and nephrocalcinosis. In 18 months follow up with alkali therapy, she had good weight gain and growth velocity. Keywords: growth retardation; hypokalemia; nephrocalcinosis; renal tubular acidosis.