Hyperammonemia in distal renal tubular acidosis: is it more common than we think?

The hyperammonemia in distal renal tubular acidosis, previously only described in two cases, is considered an unusual occurrence. After the report published in 2005, we observed plasma ammonia levels above normal range during metabolic decompensation in two other consecutive pediatric patients suffering from distal renal tubular acidosis. The ammonia plasma levels returned to normal range after treatment with sodium bicarbonate and potassium salt. In distal renal tubular acidosis, hyperammonemia is probably the result of an imbalance between the increased ammonia synthesis, in response to metabolic acidosis, and the impaired ammonia excretion, typical of distal renal tubular acidosis. According to this physiopathological mechanism, our observation shows that hyperammonemia is not an uncommon finding in distal renal tubular acidosis, and should be included among differential diagnosis of hyperammonemia in infants and children.

Hyperkalemia after acute metabolic decompensation in two children with vitamin B12-unresponsive methylmalonic acidemia and normal renal function

The patients affected by vitamin B12-unresponsive methylmalonic acidemia (MMA) on the long run develop chronic renal disease with interstitial nephropathy and progressive renal insufficiency. The mechanism of nephrotoxicity in vitamin B12-unresponsive MMA is not yet known. Chronic hyporeninemic hypoaldosteronism has been found in many cases of methylmalonic acidemia, hyperkalemia and renal tubular acidosis type 4. We report 2 patients affected by B12-unresponsive methylmalonic acidemia diagnosed at the age of 23 months and 5 years, respectively, with normal glomerular filtration and function. They showed hyporeninemic hypoaldosteronism and significant hyperkalemia requiring sodium potassium exchange resin (Kayexalate) therapy after an episode of metabolic decompensation leading to diagnosis of MMA. In both children, hyporeninemic hypoaldosteronism and hyperkalemia disappeared after 6 months of good metabolic control.

Hemolytic uremic syndrome in an infant following Bordetella pertussis infection

Reported here is the case of a 6-week-old female infant with a severe Bordetella pertussis infection requiring supportive pressure-positive ventilation in the intensive care unit. After being discharged from the intensive care unit, she developed hemolytic anemia, thrombocytopenia and acute renal failure, which suggested a diagnosis of hemolytic uremic syndrome. The clinical outcome was favorable with no renal consequences. This case suggests there may be a direct cause-effect relationship between B. pertussis infection and hemolytic uremic syndrome.

Pre- and post-dialysis quantitative dosage of thymidine in urine and plasma of a MNGIE patient by using HPLC-ESI-MS/MS

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is an autosomal recessive disorder characterized by severe gastrointestinal dysmotility, cachexia, ptosis, ophthalmoparesis, peripheral neuropathy and leukoencephalopathy. The disease is due to a thymidine phosphorylase defect. This enzyme catalyses the phosphorolysis of thymidine to thymine and deoxyribose 1-phosphate. For this reason, increased levels of thymidine in plasma and urine are found in MNGIE patients. Haemodialysis can reduce circulating plasma thymidine levels and can be beneficial in some MNGIE patients. We developed a fast analytical method based on HPLC-ESI-MS/MS capable of identifying pyrimidine nucleotides (thymine, cytosine, uracil) and nucleosides (thymidine, citidine, uridine) in plasma and urine after direct dilution of the samples without pre-treatment. In the patient studied, we observed a significant reduction of plasmatic and urinary thymidine levels during and after dialysis. However, we noted a progressive reduction of the initial thymidine level after some dialytic trials. This method will be useful not only for thymidine level follow-up during dialysis in MNGIE patients but also for the improvement of the diagnosis or diagnostic suspect in other pyrimidine defects such as dihydropyrimidine dehydrogenase deficiency, dihydropyrimidinase deficiency and ureidopropionase deficiency.

Hyperammonaemia in a child with distal renal tubular acidosis

A 5-month-old girl with distal renal tubular acidosis (RTA) and hyperammonaemia that had lasted for 12 days, despite metabolic acidosis correction, is presented in this report. The patient showed failure to thrive, poor feeding, hypotonia and vomiting crisis in absence of inborn errors of metabolism. Probably, hyperammonaemia was the result of an imbalance between the increased ammonia synthesis, in response to metabolic acidosis, and the impaired ammonia excretion, typical of distal RTA. Our case confirms that hyperammonaemia may be observed in distal RTA, mimicking an inborn error of metabolism, and it underlines that hyperammonaemia may persist several days after metabolic acidosis correction.

Clinical findings and biochemical and molecular analysis of four patients with holocarboxylase synthetase deficiency

Holocarboxylase synthetase (HLCS) deficiency (HLCSD) is a rare autosomal recessive disorder of biotin metabolism. HLCS catalyzes the biotinylation of the four human biotin-dependent carboxylases. Using the newly available human genomic sequence, we report the map of HLCS genomic structure and the predicted exon/intron boundaries. Moreover, the molecular studies of four patients (two Italians, one Iranian, and one Australian) affected by HLCS deficiency are here reported. The clinical findings, the age of onset, and response to biotin treatment differed between our patients. The diagnosis was made by organic acid analysis and confirmed by enzymatic analysis in three patients. Six mutations in the HLCS gene were identified, including two novel (N511K and G582R) and four known missense mutations (L216R, R508W, V550M, and G581S). Five of the mutations are localized within the HLCS biotin-binding domain, whereas the L216R amino acid change is located in the N-terminal region outside of the putative biotin-binding domain. This mutation, previously reported in a heterozygous state, was detected for the first time in a patient with homozygous status. The patient's severe clinical phenotype and partial responsiveness to biotin support a genotype-phenotype correlation through the involvement of residues of the N-terminal region in a substrate specificity recognition or regulation of the HLCS enzyme.

Effect of ramipril in a patient with glycogen storage disease type I and nephrotic-range proteinuria

We studied the effect of ramipril on urinary protein excretion and arterial pressure in a 27-year-old patient with GSD Ia and heavy proteinuria (2-3 g /24 h). Ramipril therapy resulted in an important reduction of proteinuria (0.3-0.5 g/24 h): no changes were observed in arterial pressure and renal function during the 12-month follow-up. We conclude that treatment with ramipril can be employed effectively and safely in GSD Ia patients with nephrotic-range proteinuria.

[Severe and unusual clinical manifestations of intolerance to cow's milk protein in 3 patients under 12 months of age]

Cow's Milk Protein Allergy/Intolerance (CMPA/CMPI), due to immunologic hypersensitivity to one or more milk proteins, includes several clinical presentations. We report three unusual cases of CMPA/CMPI, illustrating uncommon and misinterpreted clinical features, with the purpose to provide further evidence of the variety of CMPA/CMPI presentations in infancy. Our study shows that extreme care in assessing the clinical and feeding history of the patient is extremely important for the prompt and correct diagnosis of CMPA/CMPI in infants.

Efficacy of hemodiafiltration in a child with severe lactic acidosis due to thiamine deficiency

We report the case of a child in whom severe lactic acidosis (LA) and hyperammonemia developed after twenty days of total parenteral nutrition (TPN) for diffuse esophageal damage due to caustic ingestion. The revision of TPN preparation revealed that thiamine was never included and the hypothesis of thiamine deficiency was later confirmed measuring the serum thiamine level. Because severe metabolic acidosis the dialytic treatment with hemodiafiltration (HDF) and bicarbonate infusion were performed: the patient very quickly recovered with dramatic reestablishment of the acid-basic balance. Thiamine administration restored lactate metabolism. We emphasize that HDF is a useful and prompt treatment for LA to get over the critical phase of neurological and cardiological damage.

[Acute gouty arthritis in adolescents with renal transplants]

Hyperuricemia is a common metabolic abnormality in subjects with renal transplantation: in fact in transplanted adults receiving immunosuppressive and diuretic drugs the frequency of hyperuricemia varied from 30 to 84% according to treatment. Conversely, the gout is an uncommon eventuality, representing less than 10%; predisposing factors are impaired renal function and older age. In the younger patients with renal transplantation hyperuricemia is also frequent, but the gout doesn't considered a possible complication in paediatric age. We reported our observation of 5 patients (3 males and 2 females), 13-18 years old who developed gout 2-84 months after renal transplantation. All the patients were receiving cyclosporine, 4 even with prednisone and azathioprine. Two patients were treated with furosemide because hypertension. The average of uric acid serum levels in the post transplantation follow-up was 7 +/- 2 mg/dl; at the moment of gout attack the uric acid serum levels raised to 12 +/- 1 mg/dl. The arthritis diagnosis were made by clinical, laboratory and instrumental data (Rx and US). In the most severe cases, uricasi therapy resolved clinical picture. The analysis of immunosuppressive and diuretic treatment, renal function and dietary uses induces us to think that the gout episode may be the result of many concomitant factors, in adolescents with renal transplant.

Genetic mapping to 10q23.3-q24.2, in a large Italian pedigree, of a new syndrome showing bilateral cataracts, gastroesophageal reflux, and spastic paraparesis with amyotrophy

We have recently observed a large pedigree with a new rare autosomal dominant spastic paraparesis. In three subsequent generations, 13 affected individuals presented with bilateral cataracts, gastroesophageal reflux with persistent vomiting, and spastic paraparesis with amyotrophy. Bilateral cataracts occurred in all affected individuals, with the exception of one patient who presented with a chorioretinal dystrophy, whereas clinical signs of spastic paraparesis showed a variable expressivity. Using a genomewide mapping approach, we mapped the disorder to the long arm of chromosome 10 on band q23.3-q24.2, in a 12-cM chromosomal region where additional neurologic disorders have been localized. The spectrum of phenotypic manifestations in this family is reminiscent of a smaller pedigree, reported recently, confirming the possibility of a new syndrome. Finally, the anticipation of symptoms suggests that an unstable trinucleotide repeat may be responsible for the condition.

Report of a new case of axial mesodermal dysplasia complex

We present a female child with phenotypical and clinical features of the axial mesodermal dysplasia complex. Typical manifestations of both the Goldenhar syndrome and the caudal regression syndrome are present in this complex. Only a few reports have described patients with this pattern of malformations localized in both the cranial and caudal regions. Our case represents a mild form of the complex and may contribute to a better delineation of this condition.

[Vitamin D-dependent type-1 rickets: diagnosis and treatment of a further case]

We describe a child with vitamin D dependent rickets type 1, who developed clinical signs of the disease at three months of age. The principal manifestations were hypocalcemia and seizure with EEG abnormalities. The circulating level of 1 alpha, 25 (OH)2D3 was low despite a normal level of 25 (OH)D3 and an adequate vitamin D supplementation. The patient responded to calcium gluconate infusions and pharmacologic doses of 1 alpha, 25 (OH)2D3 and a normalization of calcemia was obtained. After six months the therapy was progressively reduced to physiological dosage with optimal metabolic control. The patient is now 2.5 years old and receive a maintenance dose of calcitriol of 0.125 mcg/day. His clinical, biochemical and radiologic features are normal.

Failure of early dextromethorphan and sodium benzoate therapy in an infant with nonketotic hyperglycinemia

We report an infant with neonatal nonketotic hyperglycinemia (NKH), diagnosed early and treated with dextromethorphan (DM) and sodium benzoate therapy from the 65th hour of life. Initially the patient responded to treatment showing clinical and electroencephalographic improvement: myoclonic jerks disappeared, muscular tone, reactivity to stimuli and spontaneous movements increased, assisted ventilation was no longer necessary and bottle feeding was initiated successfully; on EEG the suppression-burst pattern disappeared and the background activity was well-organized. At three months of age he developed flexor spasms and hypsarrhythmia. In spite of increasing doses of DM as high as 40 mg/kg/day and persistent therapy with sodium benzoate the child progressively deteriorated and died at the age of 5 months and 7 days. We stress that the adverse clinical course occurred in our patient even though DM and sodium benzoate therapy was started much earlier than in other reported cases. It is possible that prenatal brain damage and probable genetic variants (i.e. absent or minimal residual enzymatic activity and interindividual variations in DM metabolism) affect the response to therapy.

[An echocardiographic study of the left ventricular functional indices in pediatric patients on hemodialysis and in treatment with recombinant human erythropoietin (r-HuEPO)]

Recombinant human erythropoietin (r-HuEPO) is efficient in the treatment of anaemia in chronic renal failure on hemodialysis. We investigated the changes in cardiac function under r-HuEPO therapy using echocardiography. Seven patients with severe renal anaemia (Ht 19%) were treated with 50 U/kg r-HuEPO EV three times/week. Echocardiographic studies were performed in the anemic state and when hematocrit values were stable at levels (Ht 30%). Left ventricular function as showed by fractional shortening (D%) improved, the thickness of the interventricular septum and left ventricular hypertrophy were reduced. Our data indicate that the correction of renal anaemia by r-HuEPO can improve myocardial function in patients on maintenance hemodialysis.

Changes in Blood Pressure Reactivity and 24-Hour Blood Pressure Profile Occurring at Puberty

To evaluate blood pressure reactivity in children and its changes in adolescents, the acute pressor response to a video-game stress test and the noninvasive ambulatory blood pressure monitoring were evaluated in 62 healthy children divided into three age groups. Basal blood pressure values were measured according to the NIH Task Force. With baseline measures and body mass index controlled for, analysis of covariance showed that the video game provoked significant and incremental cardiovascular reac tivity across the games in adolescents when compared with the two other groups of children. The same group of children showed also a significantly higher systolic ambu latory pressure during the daytime, whereas no significant difference was observed by basal BP measurement.

In conclusion an increased reactivity to external stimuli was observed in adolescents, and this pattern was strictly associated with a higher daily blood pressure.

Changes in blood pressure reactivity and 24-hour blood pressure profile occurring at puberty

To evaluate blood pressure reactivity in children and its changes in adolescents, the acute pressor response to a video-game stress test and the noninvasive ambulatory blood pressure monitoring were evaluated in 62 healthy children divided into three age groups. Basal blood pressure values were measured according to the NIH Task Force. With baseline measures and body mass index controlled for, analysis of covariance showed that the video game provoked significant and incremental cardiovascular reactivity across the games in adolescents when compared with the two other groups of children. The same group of children showed also a significantly higher systolic ambulatory pressure during the daytime, whereas no significant difference was observed by basal BP measurement. In conclusion an increased reactivity to external stimuli was observed in adolescents, and this pattern was strictly associated with a higher daily blood pressure.

[Influence of iron metabolism on the efficacy of r-HuEPO (recombinant human erythropoietin) treatment of anemia in children on hemodialysis]

Recombinant Human Erythropoietin (r-HuEPO) is efficient in the treatment of anaemia in terminal renal failure under dialysis. Five pediatric patients, who were under periodic hemodialysis, were treated and the interaction between the metabolism of iron and the response to r-HuEPO was studied in particular. In two patients it was noticed that a significant reduction of hematic ferritin levels occurred, while an efficient erythropoietic activity was maintained. On the contrary, three patients showed iron deficiency characterized by a reduced percentage of total transferrin saturation in the plasma, in the presence of high levels of ferritin in the blood. Also discovered was a missing increase or even a fall of the hemoglobin values that were obtained till now. In these cases, the increase of the hormone dose didn't lead to an improvement, that could only be obtained by the oral or parenteral administration of iron. The Authors in conclusion affirm that iron deficiency is the first cause to be searched for and to be corrected in the presence of missing hemoglobin increase even with adequate doses of r-HuEPO.

[Changes in the ambulatory arterial pressure of normotensive obese children]

Obesity represents an important risk factor for cardiovascular disease and in children it is often associated to the future development of essential hypertension. To evaluate the early hemodynamic alterations in obese normotensive children, ambulatory monitoring was performed in 18 obese children aged 9.6 +/- 2.9 and in 33 controls of equivalent age by ICR 5200 (Spacelabs, USA). Blood pressure daily curves in the two groups were compared by MANOVA. Basal blood pressure did not differ in the two groups (115 +/- 17 mmHg and 79 +/- 7 mmHg respectively systolic and diastolic in controls and 115 +/- 12 mmHg and 79 +/- 6 mmHg in obese children). On the contrary ambulatory monitoring showed higher systolic values in obese children when compared to controls (112 +/- 7 versus 107 +/- 7, p less than 0.04) (MANOVA test, p less than 0.03). The difference was observed both during the day time (115 +/- 6 vs 111 +/- 7, p less than 0.03) and during the night (107 +/- 9 vs 102 +/- 8, p less than 0.5). No differences in diastolic pressure and in heart rate were observed. Those findings indicate that in obese children blood pressure alterations unrecognized at usual blood pressure checks are detectable by ambulatory 24 hour monitoring.

[Pulmonary calcification in vitamin D poisoning in an infant]

We describe the case of a child aged 11 months with vitamin D intoxication and hypercalcemia, who developed acute renal failure and dyspnea. Chest X-rays showed interstitial changes compatible with either pulmonary alveolar proteinosis or pulmonary edema. The hypercalcemia suggested the possibility of metastatic calcifications of the lung. This hypothesis was subsequently confirmed by the progressive disappearance of pulmonary findings as calcemic levels returned to normal values... Our report emphasize the opportunity of studying the respiratory system in each patient with hypercalcemia, whichever the etiology may be.

[Economic and social aspects of pediatric dialysis in Italy]

Rarely in italian medical journals have been discussed the social and economic problems related to dialysis much less the ones related pediatric dialysis. On the contrary, we believe that these problems hold a great importance due to their obvious consequences on the family structure, society and most of all on the psychophysical development of the affected child. Present structures of pediatric centers in Italy have been studied along with the available facilities, their spreading over the national territory and consequent transport problems. We also provided data regarding social and scholastic rehabilitation of the little patients as well as the effects of followed treatments on the family economy. Through these we can say that at the moment in Italy the 50% only of the children are treated in pediatric centers, which are still unequally distributed with a major concentration in the North, followed by the South and the Center Italy as last. However, it is important to notice that in every Center the child is seen as an individual and many efforts are done to reach his complete welfare. This purpose justify the presence, besides the specialized medical and nursing staff, of many dietitian, psychologist, teachers, play teachers, social workers. Results of a good recovery are evident in the sphere of the little patients, at school as at home, even if it is still difficult to evaluate a following complete integration in the work world. Still far away from solution is transplant problem in Italy: centers are insufficient and not perfectly working; patients suffer long waiting-lists; which causes to find the solution of their problem abroad.

[Schoenlein-Henoch syndrome. Renal involvement and prognosis]

We have studied the incidence of renal involvement, the severity and the clinical course of nephropathy in 83 children, 47 males and 36 females, aged from 2 to 13 years, who were under observation for SSH at the II Pediatric Clinic, Florence University. In 72.3% of cases, we have not observed any sign of renal involvement, at least within 6 months of onset of the syndrome. In 16.3% we have observed persistent urinary abnormalities: these findings have returned to normal within 1 year in 13 children and within 3 years in one child. In 10.8% of cases, a nephropathy has appeared, in all of the cases within 3 months of onset. Only one case has developed renal failure 5 years after onset. We can conclude that a good correlation exists between clinical manifestations of this disease and histopathologic changes; that therapy is of little value in modifying the clinical course; that renal failure is a rare occurrence.

[Cystic renal disease in childhood]

In the last five years, in the Surgery Pediatric Department and in the Pediatric Nephrology and Dialysis Service of the Florence University, have been observed 13 patients with cystic renal diseases. In every single case, for the diagnosis we have considered the age of the patients and the examinations made to them. We payed attention mostly to the echography considered the main diagnostic examination, even in prenatal age.

[Osteodystrophy in children with chronic renal insufficiency in dialysis therapy]

One of the most important complication of patients with chronic renal failure is osteodystrophy. This causes skeletal deformities, growth failure, bone pain and decreased physical activity. Osteodystrophy is more frequent among children than uraemic adults. In fact, 50-80% of children with chronic renal failure may occur in metabolic bone disease and the incidence tends to be higher in those children who have been in uraemic state for a long time before starting chronic haemodialysis. Osteodystrophy is a result of: 1) lesions of rickets; 2) lesions of osteitis fibrosa: 3) osteosclerosis. In contrast to adult, metastatic calcifications are virtually never observed in uraemic children. Hyperphosphoraemia, that is secondary to the reduction of G.F.R., may be the principal responsible of hyperparathyroidism that is the main cause of osteodystrophy. Hyperparathyroidism is also maintained and increased by deficit of 1,25(OH)2D3 which is responsible for lesions of rickets. Haemodialysis may markedly improve osteitis fibrosa and it is efficacious in reversing the mineral defect. Dialysate calcium concentration should be maintained at approximately 3,5 mEq/l. In this case we can raise serum calcium. On the contrary dialysate has to be lacking in phosphorus to correct hyperphosphoraemia. It must be noted that we have to prepare a dialysate with deionized water lacking in aluminum to avoid encephalopathy compliance.

Prekallikein and kallikrein inhibitor in liver cirrhosis and hepatitis

Plasma prekallikrein (kallikreinogen) and kallikrein inhibitor, assayed with the kaolin activable esterase method, have been evaluated in 20 patients with hepatic cirrhosis, in 12 cases with jaundice from acute viral hepatitis, and in 9 normal. A significant reduction of the plasma prekallikrein in cirrhosis has been found. A lowering of plasma prekallikrein has also been observed in viral hepatitis; in this condition, however, the modifications were less important than those obtained in cirrhosis. In three cases of hepatitis, the behaviour of the plasma prekallikrein and kallikrein inhibitor have been controlled during the period of the disease and compared with the behaviour of some conventional parameters, such as serum transaminases and bilirubin. An important increase of the prekallikrein level has been observed during the improvement of hepatitis. These data confirm the implication of the prekallikrein-kallikrein system in severe liver diseases, and indirectly points out the role of the liver in maintaining the physiological balance of the kallikrein system.