End Points for Clinical Trials in Primary Hyperoxaluria.

Patients with primary hyperoxaluria experience kidney stones from a young age and can develop progressive oxalate nephropathy. Progression to kidney failure often develops over a number of years, and is associated with systemic oxalosis, intensive dialysis, and often combined kidney and liver transplantation. There are no therapies approved by the Food and Drug Association. Thus, the Kidney Health Initiative, in partnership with the Oxalosis and Hyperoxaluria Foundation, initiated a project to identify end points for clinical trials. A workgroup of physicians, scientists, patients with primary hyperoxaluria, industry, and United States regulators critically examined the published literature for clinical outcomes and potential surrogate end points that could be used to evaluate new treatments. Kidney stones, change in eGFR, urine oxalate, and plasma oxalate were the strongest candidate end points. Kidney stones affect how patients with primary hyperoxaluria feel and function, but standards for measurement and monitoring are lacking. Primary hyperoxaluria registry data suggest that eGFR decline in most patients is gradual, but can be unpredictable. Epidemiologic data show a strong relationship between urine oxalate and long-term kidney function loss. Urine oxalate is reasonably likely to predict clinical benefit, due to its causal role in stone formation and kidney damage in CKD stages 1-3a, and plasma oxalate is likely associated with risk of systemic oxalosis in CKD 3b-5. Change in slope of eGFR could be considered the equivalent of a clinically meaningful end point in support of traditional approval. A substantial change in urine oxalate as a surrogate end point could support traditional approval in patients with primary hyperoxaluria type 1 and CKD stages 1-3a. A substantial change in markedly elevated plasma oxalate could support accelerated approval in patients with primary hyperoxaluria and CKD stages 3b-5. Primary hyperoxaluria type 1 accounts for the preponderance of available data, thus heavily influences the conclusions. Addressing gaps in data will further facilitate testing of promising new treatments, accelerating improved outcomes for patients with primary hyperoxaluria.

Subclinical myocardial disease in patients with primary hyperoxaluria and preserved left ventricular ejection fraction: a two-dimensional speckle-tracking imaging study.

BACKGROUND: Primary hyperoxaluria (PH) is characterized by progressive chronic kidney disease (CKD) and systemic oxalate deposition. Myocardial dysfunction might be present early in the course of the disease. However, this hypothesis has not yet been tested in the PH population. Therefore, we aimed to determine whether strain imaging using two-dimensional speckle tracking echocardiography (2D-STE) might detect subclinical myocardial disease in otherwise asymptomatic PH patients. METHODS: Prospective study of pediatric and adolescent PH patients with preserved LV ejection fraction (LV EF) and without renal replacement therapy. Subjects underwent conventional echocardiography and 2D-STE. Global (GLS) and segmental peak systolic LV longitudinal strain (LS) measurements were obtained. Data were compared with age- and gender-matched controls, and Z-scores were calculated as appropriate. RESULTS: Fifteen PH patients (age 14.1 ± 5.9 years; 13/15 in CKD stages 1-2) were studied. Although LV EF was preserved (63 ± 6%) in patients, GLS was significantly impaired (GLS - 17.1 ± 2.2% vs - 22.4 ± 1.9%, p < 0.001). This was mainly due to decreased LS values in the apical segments (p < 0.05). Echocardiographic indices of ventricular wall thickness were significantly increased in patients compared to controls (all p < 0.03). GLS correlated significantly with Z-scores of diastolic interventricular wall thickness (r = - 0.57, p = 0.025) and moderately with serum creatinine levels (r = 0.53, p = 0.044). No correlation was found between GLS and blood pressure measurements. CONCLUSIONS: Subclinical myocardial disease is already present early in the course of disease in PH patients with preserved LV EF and some degree of renal dysfunction, but without overt systemic oxalosis. Current recommendations to screen only PH patients with advanced CKD for cardiac disease should be revised accordingly.

Skin microvascular dysfunction as an early cardiovascular marker in primary hyperoxaluria type I.

BACKGROUND: Primary hyperoxaluria type 1 (PH1) is an orphan inborn error of oxalate metabolism leading to hyperoxaluria, progressive renal failure, oxalate deposition, and increased cardiovascular complications. As endothelial dysfunction and arterial stiffness are early markers of cardiovascular risk, we investigated early endothelial and vascular dysfunction in young PH1 patients either under conservative treatment (PH1-Cons) or after combined kidney liver transplantation (PH1-T) in comparison to healthy controls (Cont-H) and patients with a past of renal transplantation (Cont-T). METHODS: Skin microvascular function was non-invasively assessed by laser Doppler flowmetry before and after stimulation by current, thermal, or pharmacological (nitroprussiate (SNP) or acetylcholine (Ach)) stimuli in young PH1 patients and controls. RESULTS: Seven PH1-Cons (6 F, median age 18.2) and 6 PH1-T (2 F, median age 13.3) were compared to 96 Cont-H (51 F, median age 14.2) and 6 Cont-T (4 F, median age 14.5). The endothelium-independent vasodilatation (SNP) was severely decreased in PH1-T compared to Cont-H. Ach, current-induced vasodilatation (CIV), and thermal response was increased in PH1-Cons and Cont-T compared to controls. CONCLUSIONS: PH1-T patients displayed severely decreased smooth muscle capacity to vasodilate. An exacerbated endothelial-dependent vasodilation suggests a role for silent inflammation in the early dysfunction of microcirculation observed in PH1-Cons and Cont-T.

[A special form of pancytopenia]. / Une forme particulière de pancytopénie.

Primary hyperoxaluria is a rare disease whose incidence is estimated at less than 1 cases/million inhabitants/year. This is a congenital abnormality of hepatic metabolism leading to an endogenous overproduction of oxalate with excess urinary excretion. We report the case of a 43-year-old patient, was followed to end-stage renal disease hemodialysis, consulting for anemic syndrome with mucocutaneous pallor. Laboratory tests found pancytopenia with aplastic anemia. Bone marrow was difficult to achieve, bringing medullary blood hyperdilué and uninterpretable . Radiographs showed a homogeneous splenomegaly and small dedifferentiated a kidney marrow biopsy was performed. Histological examination revealed a myelofibrosis and birefringent crystals in polarized light, diagnosis retained: spinal oxalosis.

Molecular analysis of the AGXT gene in patients suspected with hyperoxaluria type 1 and three novel mutations from Turkey.

Primary hyperoxaluria type 1 (PH1) is a rare, autosomal recessive disease, caused by the defect of AGXT gene encoding hepatic peroxisomal alanine glyoxylateaminotransferase (AGT). This enzyme is responsible for the conversion of glyoxylate to glycine. The diagnosis of PH1 should be suspected in infants and children with nephrocalcinosis or nephrolithiasis. Early diagnosis and treatment is crucial in preventing disease progression to end stage kidney disease (ESKD). In this study, AGXT gene sequence analyses were performed in 82 patients who were clinically suspected (hyperoxaluria and nephrolithiasis or nephrocalcinosis with or without renal impairment) to have PH1. Disease causing mutations have been found in fifteen patients from thirteen families (18%). Novel mutations have been found (c.458T>A (p.L153X), c.733_734delAA (p.Lys245Valfs*11), c.52 C>T (p.L18F)) in three of 13 families. There were 3-year lag time between initial symptoms and the time of PH1 is suspected; additionally, 5.5-year lag time between initial symptoms and definitive diagnosis. Consanguinity was detected in 77% of the patients with mutation. After genetic diagnosis, one patient received combined kidney and liver transplantation. AGXT gene sequencing is now the choice of diagnosis of PH1 due to its non-invasive nature compared to liver enzyme assay. Early diagnosis and accurate treatment in PH1 is important for better patient outcomes.

DETAILED CLINICAL PHENOTYPING OF OXALATE MACULOPATHY IN PRIMARY HYPEROXALURIA TYPE 1 AND REVIEW OF THE LITERATURE.

PURPOSE: To describe the structural and functional characteristics of oxalate retinopathy. METHODS: Five patients with molecularly confirmed primary hyperoxaluria (PH) Type 1 underwent multimodal retinal imaging (spectral-domain optical coherence tomography, white light, and HRA multispectral imaging) and functional testing, including color vision testing, Goldmann perimetry, and International Society for Clinical Electrophysiology of Vision standard electrophysiological testing. RESULTS: Four distinct retinal phenotypes are presented. One patient with a c.[33dupC]; c.[731T>C] mutation showed bilateral perifoveal retinal pigment epithelium hyperplasia. The fundus in the four other patients, all of whom share an identical homozygous c.[33dupC] mutation, ranged from normal to bilateral widespread distribution of retinal crystals and confluent macular retinal pigment epithelium hyperplasia with subfoveal fibrosis. All patients who had developed end-stage renal disease showed some sign of retinopathy, more severe with earlier onset. CONCLUSION: Retinopathy in PH Type 1 shows considerable interindividual variation. No correlation between genotype and retinal phenotype was detected. Oxalate crystals at the level of the retinal pigment epithelium seem to be irreversible. A proposed clinical grading system of oxalate maculopathy, based on a literature review, may provide clinicians with a tool to better predict visual function and prognosis.

Natural and Unnatural Compounds Rescue Folding Defects of Human Alanine: Glyoxylate Aminotransferase Leading to Primary Hyperoxaluria Type I.

The functional deficit of alanine:glyoxylate aminotransferase (AGT) in human hepatocytes leads to a rare recessive disorder named primary hyperoxaluria type I (PH1). PH1 is characterized by the progressive accumulation and deposition of calcium oxalate stones in the kidneys and urinary tract, leading to a life-threatening and potentially fatal condition. In the last decades, substantial progress in the clarification of the molecular pathogenesis of the disease have been made. They resulted in the understanding that many mutations cause AGT deficiency by affecting the folding pathway of the protein leading to a reduced expression level, an increased aggregation propensity, and/or an aberrant mitochondrial localization. Thus, PH1 can be considered a misfolding disease and possibly treated by approaches aimed at counteracting the conformational defects of the variants. In this review, we summarize recent advances in the development of new strategies to identify molecules able to rescue AGT folding and trafficking either by acting as pharmacological chaperones or by preventing the mistargeting of the protein.

Predictors of Incident ESRD among Patients with Primary Hyperoxaluria Presenting Prior to Kidney Failure.

BACKGROUND AND OBJECTIVES: Overproduction of oxalate in patients with primary hyperoxaluria (PH) leads to calcium oxalate deposition in the kidney and ESRD in a substantial number of cases. However, the key determinants for renal outcome remain unclear. Thus, we performed a retrospective analysis to identify predictors for renal outcome among patients with PH participating in the Rare Kidney Stone Consortium (RKSC) PH Registry. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We characterized clinical and laboratory features of patients enrolled in the RKSC PH Registry. We assessed correlation between urinary measures and eGFR at diagnosis by Spearman rank correlation and estimated renal survival using the Kaplan-Meier method. We determined factors associated with renal survival by Cox proportional hazard models. RESULTS: Of 409 patients enrolled in the RKSC Registry as of March 2014, we excluded 112 patients who had ESRD at PH diagnosis from analysis. Among the remaining 297 patients, 65% had PH type 1, 12% had type 2, 13% had type 3, and 11% had unclassified PH. Median (25th, 75th percentile) age at PH diagnosis was 8.1 (4.0, 18.2) years with an eGFR of 73.0 (56.4, 97.5) ml/min per 1.73 m(2) and urinary oxalate excretion rate of 1.64 (1.11, 2.44) mmol/1.73 m(2) per 24 hours. During a median follow-up of 3.9 (1.0, 12.8) years, 59 (20%) patients developed ESRD. Urinary oxalate excretion at diagnosis stratified by quartile was strongly associated with incident ESRD (hazard ratio [HR], 3.4; 95% confidence interval [95% CI], 1.4 to 7.9). During follow-up there was a significant association between urinary oxalate quartile (Q) and incident ESRD (Q4 versus Q1: HR, 3.3; 95% CI, 1.2 to 9.3). This association remained even when adjusted for sex, age, and baseline eGFR (HR, 4.2; 95% CI, 1.6 to 10.8). CONCLUSIONS: Among patients with PH, higher urinary oxalate excretion is predictive of poor renal outcome.

Renal function can be impaired in children with primary hyperoxaluria type 3.

BACKGROUND: Primary hyperoxaluria type 3 (PH3) is characterized by mutations in the 4-hydroxy-2-oxoglutarate aldolase (HOGA1) gene. PH3 patients are believed to present with a less severe phenotype than those with PH1 and PH2, but the clinical characteristics of PH3 patients have yet to be defined in sufficient detail. The aim of this study was to report our experience with PH3. METHODS: Genetic analysis of HOGA1 was performed in patients with a high clinical suspicion of PH after the presence of mutations in the alanine-glyoxylate aminotransferase gene had been ruled out. Clinical, biochemical and genetic data of the seven patients identified with HOGA1 mutations were subsequently retrospectively reviewed. RESULTS: Among the seven patients identified with HOGA1 mutations the median onset of clinical symptoms was 1.8 (range 0.4-9.8) years. Five patients initially presented with urolithiasis, and two other patients presented with urinary tract infection. All patients experienced persistent hyperoxaluria. Seven mutations were found in HOGA1, including two previously unreported ones, c.834 + 1G > T and c.3G > A. At last follow-up, two patients had impaired renal function based on estimated glomerular filtration rates (GFRs) of 77 and 83 mL/min per 1.73 m(2), respectively. CONCLUSIONS: We found that the GFR was significantly impaired in two of our seven patients with PH3 diagnosed during childhood. This finding is in contrast to the early-impaired renal function in PH1 and PH2 and appears to refute to preliminary reassuring data on renal function in PH3.

Cardiac involvement of primary hyperoxaluria accompanied by non-compaction cardiomyopathy and patent ductus arteriosus.

Primary hyperoxaluria is a rare hereditary metabolic disorder resulting in accumulation of calcium oxalate in visceral organs, including the heart. We report a 19-year-old male with non- compaction cardiomyopathy combined with patent ductus arteriosus awaiting combined liver-kidney transplantation for primary hyperoxaluria. After surgical closure of the patent ductus arteriosus, the patient underwent a successful renal and subsequent liver transplantation. The presence of hypertrophic cardiomyopathy in hyperoxaluria patients has been reported before, but this is the first report of non-compaction myocardium with patent ductus arteriosus in a patient with primary hyperoxaluria. At the third month after combined liver and renal transplantation, improvement in cardiac functions were observed. Primary hyperoxaluria is a clinical entity to be taken into consideration in differential diagnosis of hypertrophied myocardium with high myocardial echocardiographic intensity. In cases of hyperoxaluria, additional congenital abnormalities may complicate the clinical picture.

Sustained pyridoxine response in primary hyperoxaluria type 1 recipients of kidney alone transplant.

Combined liver kidney transplant is the preferred transplant option for most patients with primary hyperoxaluria type 1 (PH1) given that it removes the hepatic source of oxalate production and improves renal allograft survival. However, PH1 patients homozygous for the G170R mutation can develop normal urine oxalate levels with pyridoxine therapy and may be candidates for kidney alone transplant (KTx). We examined the efficacy of pyridoxine therapy following KTx in five patients homozygous for G170R transplanted between September 1999 and July 2013. All patients were maintained on pyridoxine posttransplant. Median age at transplant was 39 years (range 33-67 years). Median follow-up posttransplant was 8.5 years (range 0.2-13.9 years). At the end of follow-up, four grafts were functioning. One graft failed 13.9 years posttransplant due to recurrent oxalate nephropathy following an acute medical illness. After tissue oxalate stores had cleared, posttransplant urine oxalate levels were <0.5 mmol/24 h the majority of times checked. Calcium oxalate crystals were noted in only 3/13 allograft biopsies. This series suggests that a subgroup of PH1 patients demonstrate sustained response to pyridoxine therapy following KTx. Therefore, pyridoxine combined with KTx should be considered for PH1 patients with a homozygous G170R mutation.

Artropatía destructiva de grandes articulaciones y calcinosis tumoral asociada a oxalosis primaria: reporte de un caso y revisión de la literatura / Large joint destructive arthropathy and tumoral calcinosis associated to primary oxalosis: case report and literature review

Se presenta el caso de artropatía destructiva de caderas y hombros con calcinosis tumoral asociada a depósitos de oxalato de calcio en un paciente con oxalosis primaria e insuficiencia renal terminal en hemodiálisis(AU)

A case of destructive arthropathy of hips and shoulders with tumoral calcinosis associated with calcium oxalate deposits in a patient with primary oxalosis and end stage renal disease on hemodialysis(AU)

Oxalosis involving the skin: case report and literature review.

BACKGROUND: The primary hyperoxalurias are a group of rare autosomal recessive metabolic disorders associated with abnormal overproduction of serum oxalate and subsequent deposition in tissue. Most patients present at an early age with recurrent urolithiasis and renal failure. Vascular deposition of oxalate-producing skin manifestations, such as livedo reticularis, acrocyanosis, peripheral gangrene, and ulcerations, is typical of the primary hyperoxalurias. OBSERVATIONS: We present the case of a 38-year-old woman with end-stage renal disease receiving hemodialysis with progressive skin changes, including livedo reticularis, superficial eschars, and brawny, woody fibrosis of her extremities, who was clinically suspected to have calciphylaxis or nephrogenic systemic fibrosis. Cutaneous biopsy specimens revealed rectangular, birefringent, yellowish-brown, polarizable crystalline material suggestive of oxalate within the dermis, subcutis, and medium-size vessels along with areas of focal epidermal and superficial dermal necrosis. Her subsequent medical history was obtained and was suggestive of a diagnosis of primary hyperoxaluria. CONCLUSIONS: This case highlights the variability of clinical presentations in primary hyperoxaluria and that the disease can be diagnosed in adulthood. In addition, this case demonstrates that hyperoxaluria should be included in the differential diagnosis of calciphylaxis and nephrogenic systemic fibrosis.

Primary hyperoxaluria in a compound heterozygote infant.

BACKGROUND: Primary hyperoxaluria type 1 is a rare disorder caused by a defect in the hepatic metabolism of glyoxylate. Cases presenting in infancy are very uncommon and often have a severe course leading to early end-stage renal failure. METHODS: We treated a case of early presentation of primary hyperoxaluria type 1 and reviewed the relevant literature. RESULTS: A 4-month-old female infant was admitted to our hospital because of acute renal failure and nephrocalcinosis. Mutational analysis of alanine-glyoxylate aminotransferase gene revealed compound heterozygosity in the infant, confirming the development of primary hyperoxaluria type 1. A few weeks later, the condition of the infant worsened during an interdialytic period and died. CONCLUSIONS: Interest of this case is based on the coexistence of two mutations of alanine-glyoxylate aminotransferase gene recently reported, and it confirms the severe course of the disease when it presents in infancy. It also highlights the importance of the association of nephrocalcinosis and urolithiasis as key diagnostic manifestations of primary hyperoxaluria type 1.