Bone impairment in primary hyperoxaluria: a review

Variable treatment response to lumasiran in pediatric patients with primary hyperoxaluria type 1

BACKGROUND

Primary hyperoxaluria type 1 (PH 1) is a rare genetic condition due to mutations in the AGXT gene. This leads to an overproduction of oxalate in the liver. Hyperoxaluria often causes kidney stones, nephrocalcinosis, and chronic kidney disease. Lumasiran is a recently approved drug that reduces the hepatic oxalate production by mRNA interference.

METHODS

In this multicenter study, we evaluated the response to lumasiran treatment in PH 1 patients (n = 8) with a median age of 10.9 years (range 1.2-17.9 years), including two patients on hemodialysis. We retrospectively analyzed the reduction of urinary and plasma oxalate levels as well as changes in kidney stone events, nephrocalcinosis, and kidney function.

RESULTS

In patients without kidney failure, the median reduction of urinary oxalate was 64% (range 10-80%) and 71% (61-86%) at 6 and 12 months, respectively. However, only one patient reached urinary oxalate levels within the age-specific normal range. Two patients did not respond to lumasiran and treatment was stopped. In one of the two patients on hemodialysis, the frequency of sessions could be reduced. The only notable side effects were injection site reactions.

CONCLUSION

There was a variable response to lumasiran in PH 1. Despite a reduction of hyperoxaluria in many patients with PH 1, only one patient reached normal values and 2 of 8 patients did not respond. Regular monitoring of urinary oxalate values and registry data collection seems mandatory to monitor the efficacy and the long-term outcome of PH 1 treated with lumasiran.

Real-Life Data of 2-Year Lumasiran Use in the DAILY-LUMA Cohort

Introduction

Lumasiran is a drug used in RNA-interference (RNAi) therapy for primary hyperoxaluria type 1 (PH1). Data on its efficacy and safety mainly come from industry-sponsored trials.

Methods

For postmarketing follow-up, French authorities requested a quasi-exhaustive retrospective and prospective study over 5 years for patients receiving lumasiran, requiring the inclusion of at least 90% of patients, named as the DAILY-LUMA cohort (NCT06225882). Here, we analyzed data from all patients who were not previously included in the industry-sponsored trials and had received lumasiran for at least 2 years.

Results

We included 38 patients, 22 from DAILY-A (i.e., estimated glomerular filtration rate (eGFR) > 45 ml/min per 1.73 m2, age ≥ 6 years), 6 from DAILY-B (i.e., eGFR > 45 ml/min per 1.73 m2, age < 6 years), and 10 from DAILY-C (i.e., all ages, eGFR < 45 ml/min per 1.73 m2, 6 on dialysis). In DAILY-A and DAILY-B, decreased urinary oxalate-to-creatinine (UOx/creat) ratio, stable eGFR, and decrease in both nephrocalcinosis severity and stone numbers were observed, with a progressive tapering of conservative therapies. The decreased proportion of patients with nocturnal hydration and G-tubes overtime likely reflects improved quality of life. With a low number of patients - 2 patients on peritoneal dialysis and 3 patients with infantile oxalosis - the results are less conclusive for DAILY-C; however, in older patients, change in plasma oxalate (POx) levels is similar to previously published data. Tolerance was good with no severe side effects; injection site reactions, abdominal pain, and headaches were the main adverse events.

Conclusion

DAILY-LUMA is the largest cohort of patients receiving lumasiran in real life, confirming its safety and efficacy at 2 years.

Diagnosis and management of primary hyperoxalurias: best practices

The primary hyperoxalurias (PH 1, 2, and 3) are rare autosomal recessive disorders of glyoxylate metabolism resulting in hepatic overproduction of oxalate. Clinical presentations that should prompt consideration of PH include kidney stones, nephrocalcinosis, and kidney failure of unknown etiology, especially with echogenic kidneys on ultrasound. PH1 is the most common and severe of the primary hyperoxalurias with a high incidence of kidney failure as early as infancy. Until the recent availability of a novel RNA interference (RNAi) agent, PH care was largely supportive of eventual need for kidney/liver transplantation in PH1 and PH2. Together with the Oxalosis and Hyperoxaluria Foundation, the authors developed a diagnostic algorithm for PH1 and in this report outline best clinical practices related to its early diagnosis, supportive treatment, and long-term management, including the use of the novel RNAi. PH1-focused approaches to dialysis and kidney/liver transplantation for PH patients with progression to chronic kidney disease/kidney failure and systemic oxalosis are suggested. Therapeutic advances for this devastating disease heighten the importance of early diagnosis and informed treatment.

Primary hyperoxaluria: Description of a new oral finding and review of literature

OBJECTIVES

Oro-dental manifestations of hyperoxaluria and dental management of affected patients are rarely reported in the literature. We describe a new oral presentation of primary hyperoxaluria (PH) and review relevant literature about oro-dental manifestations and management of dental complications of hyperoxaluria.

METHODS

A case report of a 44-year-old female who presented with symptoms of temporomandibular joint dysfunction due to hyperoxaluria was described according to the CARE guidelines. In addition, an extensive search of biomedical databases (PubMed, Medline, Google Scholar, and Embase) for articles describing oro-dental manifestations and/or dental management in patients with hyperoxaluria was performed using the key words ("oral" and/or "hyperoxaluria" and/or "dental" and/or "oxalosis"). Included articles were reviewed and data about patient demographics, disease type and stage, oral and dental manifestations, and dental treatment outcome were retrieved and analyzed.

RESULTS

A total of 14 articles describing the oral and dental manifestations in 15 patients with hyperoxaluria were included. Tooth mobility, root resorption, and radiographic alterations were consistently described in all cases. Oral manifestations were described mainly in PH at late stages, and only after the onset of chronic renal disease. Dental management in all reported cases was palliative and aimed to relive pain and treat periodontal infection. Tooth loss due to extraction or uncontrolled mobility was the ultimate outcome in almost all reported cases.

CONCLUSION

Oral and dental manifestations in hyperoxaluria are rarely reported in the literature. Management of tooth mobility and root resorption in hyperoxaluria is challenging and clinical guidelines and evidence-based recommendations are lacking. Early diagnosis and treatment of hyperoxaluria might be the only effective approach to prevent dental and periodontal complications of the disease.

Bone health in children with primary hyperoxaluria type 1 following liver and kidney transplantation

Background

Primary hyperoxaluria type 1 is characterized by hepatic oxalate overproduction, leading to nephrocalcinosis, kidney stones, kidney failure and systemic oxalosis, including oxalate osteopathy. Combined liver-kidney transplantation (CLKT) and kidney after liver transplantation (KALT) were established therapeutic options to stop the devastating consequences of oxalate bone disease.

Methods

We describe a retrospective cohort of 10 children with PH1who were referred to our hospital from different countries for combined transplantation. Demographic and clinical data were collected and symptoms of bone disease, conventional radiological examinations, plasma oxalate levels and other determinants of calcium-phosphate metabolism were compared pre and post transplantation.

Results

Ten patients (7 male, median age 5.8 years, median follow-up time 8.1 years) were included in this study. Seven patients were diagnosed with infantile oxalosis and 9 patients received an intensified dialysis regime prior to transplantation. In one patient the transplanted kidney never achieved primary function and the boy remained on HD. All other patients remained without graft failure and retained stable kidney and liver function. Prior to transplantation, seven patients suffered from severe skeletal pain and three children presented with 1-3 series of pathological fractures. Pathological fractures did no longer occur in children who underwent successful CLKT or KALT. Plasma oxalate levels dropped within 6 months following Tx. Determinants of calcium-phosphorus metabolism did not differ significantly in comparison to other HD children. Seven of ten children showed a restricted growth at the time of transplantation and presented a moderate catch-up-growth at the time of last follow-up.

Conclusions

Patients with PH1 suffer from severe consequences of a disturbed bone metabolism. However, bone health and growth can partially improve following CLKT/KALT.

Multidisciplinary and multidimensional approaches to transplantation in children with rare genetic kidney diseases

In this review, we describe the multidisciplinary, multidimensional care required to optimize outcomes for pediatric transplant recipients with rare genetic kidney diseases. Transplant success, recipient survival, and improvement in quality of life depend on collaboration between patients, families, and a team of specialists with medical, as well as nonmedical expertise. A multidisciplinary transplant team composed of experts from medicine, surgery, nursing, nutrition, social services, transplant coordination, psychology, and pharmacology, is now standard in most transplant centers and is critical to the success of a transplant. In addition to these professionals, other specialists, such as cardiologists, urologists, geneticists, metabolic disease specialists, occupational therapists, case management, child life, chaplain, and palliative care services, have a crucial role to play in the preparation, surgery, and follow-up care, especially when a pediatric patient has a rare genetic disorder leading to renal involvement, and the need for transplantation. In order to describe this multidisciplinary care, we divide the genetic renal diseases into five subgroups-metabolic and tubular disorders, glomerular diseases, congenital anomalies of the kidney and urinary tract, ciliopathies including cystic diseases, and miscellaneous renal conditions; and describe for each, the need for care beyond that provided by the standard transplant team members.

Diagnosis and management of mineral and bone disorders in infants with CKD: clinical practice points from the ESPN CKD-MBD and Dialysis working groups and the Pediatric Renal Nutrition Taskforce

BACKGROUND

Infants with chronic kidney disease (CKD) form a vulnerable population who are highly prone to mineral and bone disorders (MBD) including biochemical abnormalities, growth retardation, bone deformities, and fractures. We present a position paper on the diagnosis and management of CKD-MBD in infants based on available evidence and the opinion of experts from the European Society for Paediatric Nephrology (ESPN) CKD-MBD and Dialysis working groups and the Pediatric Renal Nutrition Taskforce.

METHODS

PICO (Patient, Intervention, Comparator, Outcomes) questions were generated, and relevant literature searches performed covering a population of infants below 2 years of age with CKD stages 2-5 or on dialysis. Clinical practice points (CPPs) were developed and leveled using the American Academy of Pediatrics grading matrix. A Delphi consensus approach was followed.

RESULTS

We present 34 CPPs for diagnosis and management of CKD-MBD in infants, including dietary control of calcium and phosphate, and medications to prevent and treat CKD-MBD (native and active vitamin D, calcium supplementation, phosphate binders).

CONCLUSION

As there are few high-quality studies in this field, the strength of most statements is weak to moderate, and may need to be adapted to individual patient needs by the treating physician. Research recommendations to study key outcome measures in this unique population are suggested. A higher resolution version of the Graphical abstract is available as Supplementary information.

Oxalate in Foods: Extraction Conditions, Analytical Methods, Occurrence, and Health Implications

Oxalate is an antinutrient present in a wide range of foods, with plant products, especially green leafy vegetables, being the main sources of dietary oxalates. This compound has been largely associated with hyperoxaluria, kidney stone formation, and, in more severe cases, systematic oxalosis. Due to its impact on human health, it is extremely important to control the amount of oxalate present in foods, particularly for patients with kidney stone issues. In this review, a summary and discussion of the current knowledge on oxalate analysis, its extraction conditions, specific features of analytical methods, reported occurrence in foods, and its health implications are presented. In addition, a brief conclusion and further perspectives on whether high-oxalate foods are truly problematic and can be seen as health threats are shown.

Three Tesla magnetic resonance imaging detects oxalate osteopathy in patients with primary hyperoxaluria type I

BACKGROUND

With declining kidney function and therefore increasing plasma oxalate, patients with primary hyperoxaluria type I (PHI) are at risk to systemically deposit calcium-oxalate crystals. This systemic oxalosis may occur even at early stages of chronic kidney failure (CKD) but is difficult to detect with non-invasive imaging procedures.

METHODS

We tested if magnetic resonance imaging (MRI) is sensitive to detect oxalate deposition in bone. A 3 Tesla MRI of the left knee/tibial metaphysis was performed in 46 patients with PHI and in 12 healthy controls. In addition to the investigator's interpretation, signal intensities (SI) within a region of interest (ROI, transverse images below the level of the physis in the proximal tibial metaphysis) were measured pixelwise, and statistical parameters of their distribution were calculated. In addition, 52 parameters of texture analysis were evaluated. Plasma oxalate and CKD status were correlated to MRI findings. MRI was then implemented in routine practice.

RESULTS

Independent interpretation by investigators was consistent in most cases and clearly differentiated patients from controls. Statistically significant differences were seen between patients and controls (p < 0.05). No correlation/relation between the MRI parameters and CKD stages or Pox levels was found. However, MR imaging of oxalate osteopathy revealed changes attributed to clinical status which differed clearly to that in secondary hyperparathyroidism.

CONCLUSIONS

MRI is able to visually detect (early) oxalate osteopathy in PHI. It can be used for its monitoring and is distinguished from renal osteodystrophy. In the future, machine learning algorithms may aid in the objective assessment of oxalate deposition in bone. Graphical Abstract A higher resolution version of the Graphical abstract is available as Supplementary information.

Peripheral Blood Mononuclear Cells (PBMCs) to Dissect the Underlying Mechanisms of Bone Disease in Chronic Kidney Disease and Rare Renal Diseases

PURPOSE OF REVIEW

To describe the methods that can be used to obtain functional and mature osteoclasts from peripheral blood mononuclear cells (PBMCs) and report the data obtained with this model in two peculiar diseases, namely pediatric chronic kidney disease-associated mineral and bone disorders (CKD-MBD) and nephropathic cystinosis. To discuss future research possibilities in the field.

RECENT FINDINGS

Bone tissue undergoes continuous remodeling throughout life to maintain bone architecture; it involves two processes: bone formation and bone resorption with the coordinated activity of osteoblasts, osteoclasts, and osteocytes. Animal models fail to fully explain human bone pathophysiology during chronic kidney disease, mainly due to interspecies differences. The development of in vitro models has permitted to mimic human bone-related diseases as an alternative to in vivo models. Since 1997, osteoclasts have been generated in cell cultures, notably when culturing PBMCs with specific growth factors and cytokines (i.e., M-CSF and RANK-L), without the need for osteoblasts or stromal cells. These models may improve the global understanding of bone pathophysiology. They can be been used not only to evaluate the direct effects of cytokines, hormones, cells, or drugs on bone remodeling during CKD-MBD, but also in peculiar genetic renal diseases inducing specific bone impairment.

Natural History of Clinical, Laboratory, and Echocardiographic Parameters of a Primary Hyperoxaluria Cohort on Long Term Hemodialysis

Background: Primary hyperoxaluria type 1 (PH1) is a rare monogenic disorder characterized by excessive hepatic production of oxalate leading to recurrent nephrolithiasis, nephrocalcinosis, and progressive kidney damage, often requiring renal replacement therapy (RRT). Though systemic oxalate deposition is well-known, the natural history of PH1 during RRT has not been systematically described. In this study, we describe the clinical, laboratory, and echocardiographic features of a cohort of PH1 patients on RRT.

Methods: Patients with PH1 enrolled in the Rare Kidney Stone Consortium PH Registry who progressed to require RRT, had ≥2 plasma oxalate (pOx) measurements 3–36 months after start of RRT, and at least one pair of pOx measurements between 6 and 18 months apart were retrospectively analyzed. Clinical, echocardiographic, and laboratory results were obtained from the Registry.

Results: The 17 PH1 patients in our cohort had a mean total HD hours/week of 17.4 (SD 7.9; range 7.5–36) and a range of age of RRT start of 0.2–75.9 years. The average change in plasma oxalate (pOx) over time on RRT was −0.74 [−2.9, 1.4] μmol/L/month with the mean pOx never declining below 50 μmol/L. Over time on RRT, oxalosis progressively developed in multiple organ systems. Echocardiography performed on 13 subjects showed worsening of left ventricular global longitudinal strain correlated with pOx (p < 0.05).

Conclusions: Even when a cohort of PH1 patients were treated with intensified RRT, their predialysis pOx remained above target and they developed increasing evidence of oxalosis. Echocardiographic data suggest that cardiac dysfunction could be related to elevated pOx and may worsen over time.

Vitamin C overload may contribute to systemic oxalosis in children receiving dialysis

BACKGROUND

Malnutrition and anorexia are common in children with chronic kidney disease (CKD) and gastrostomy tubes (GT) as well as nasogastric tubes (NGT) have been recommended to maximize nutritional support. The optimal requirement of vitamin C in children with CKD remains to be defined but oxalate is a breakdown product of vitamin C. Elevated vitamin C intake and bone oxalate were identified in two formula-fed dialyzed children with negative genetic testing for primary hyperoxaluria.

METHODS

We evaluated the impact of nutritional support on serum ascorbic acid and plasma oxalate levels in 13 dialyzed infants and young children.

RESULTS

All patients were fed by GT or NGT since the first months of life; overall patients were receiving between 145 and 847% of the age-specific DRI for vitamin C. Mean serum ascorbic acid and plasma oxalate levels were elevated (244.7 ± 139.7 μM/L and 44.3 ± 23.1 μM/L, respectively), and values did not differ according to the degree of residual kidney function. Ascorbic acid levels did not correlate with oxalate levels (r = 0.44, p = 0.13).

CONCLUSIONS

Excessive vitamin C intake may contribute to oxalate accumulation in dialyzed children.

The Struggling Odyssey of Infantile Primary Hyperoxaluria

Introduction: Oxalate overproduction in Primary Hyperoxaluria type I (PH1) leads to progressive renal failure and systemic oxalate deposition. In severe infantile forms of PH1 (IPH1), end-stage renal disease (ESRD) occurs in the first years of life. Usually, the management of these infantile forms is challenging and consists in an intensive dialysis regimen followed by a liver-kidney transplantation (combined or sequential). Methods: Medical records of all infants with IPH1 reaching ESRD within the first year of life, diagnosed and followed between 2005 and 2018 in two pediatric nephrology departments in Brussels and Paris, have been reviewed. Results: Seven patients were included. They reached ESRD at a median age of 3.5 (2-7) months. Dialysis was started at a median age of 4 (2-10 months). Peritoneal dialysis (PD) was the initial treatment for 6 patients and hemodialysis (HD) for one patient. Liver transplantation (LT) was performed in all patients and kidney transplantation (KT) in six of them. A sequential strategy has been chosen in 5 patients, a combined in one. The kidney transplanted as part of the combined strategy was lost. Median age at LT and KT was 25 (10-41) months and 32.5 (26-75) months, respectively. No death occurred in the series. At the end of a median follow-up of 3 years, mean eGFR was 64 ± 29 ml/min/1.73 m². All patients presented retinal and bone lesions and five patients presented bones fractures. Conclusion: Despite encouraging survival figures, the morbidity in IPH1 patients remains extremely heavy and its management presents a huge challenge. Thanks to the newly developed RNA-interference drug, the future holds brighter prospects.

Transplantation for Primary Hyperoxaluria Type 1: Designing New Strategies in the Era of Promising Therapeutic Perspectives

Primary hyperoxaluria type 1 (PH1) is an autosomal recessive disease caused by the functional defect of alanine-glyoxylate aminotransferase that results in the overproduction of oxalate. It can be devastating especially for kidneys, leading to end-stage renal disease (ESRD) during the first 2 to 3 decades of life in most patients. Consequently, many PH1 patients need kidney transplantation. However, because PH1 is caused by a liver enzyme deficiency, the only cure of the metabolic defect is liver transplantation. Thus, current transplant strategies to treat PH1 patients with ESRD include dual liver-kidney transplantation. However, the morbidity and mortality associated with liver transplantation make these strategies far from optimal. Fortunately, a therapeutic revolution is looming. Indeed, innovative drugs are being currently tested in clinical trials, and preliminary data show impressive efficacy to reduce the hepatic overproduction of oxalate. Hopefully, with these therapies, liver transplantation will no longer be necessary. However, some patients with progressing renal disease or those who will be diagnosed with PH1 at an advanced stage of chronic kidney disease will ultimately need kidney transplantation. Here we review the current knowledge on this subject and discuss the future of kidney transplant management in PH1 patients in the era of novel therapies.

Imaging features of primary hyperoxaluria

Primary hyperoxaluria (PH) is a group of autosomal recessive diseases that affect the metabolism of glyoxalate and oxalate. As a result of the enzymatic deficiency, there is overproduction and urinary excretion of oxalate with progressive renal damage and subsequent deposition of oxalate salts in various tissues. The definitive treatment in cases of end-stage kidney disease is a combined liver and kidney transplant. Imaging features are diverse and reflect the multiple organs that might be affected. These include nephrolithiasis and nephrocalcinosis, oxalate osteopathy, as well as other findings, such as splenomegaly and oxalate deposition in the heart. In this review article, we present various imaging findings that may appear in patients with PH.

Paraplegia as a presentation of primary hyperoxaluria

30% of the patients suffering from hyperoxaluria type 1 are diagnosed only when they already had reached end-stage renal disease. We report the case of a 57-year-old woman with history of chronic kidney failure presenting with paraplegia due to spinal cord compression by thoracic mass-like lesions. Bone biopsy specimen obtained by decompressive laminectomy revealed calcium oxalate deposits. Once diagnosis of primary hyperoxaluria was confirmed, she underwent haemodialysis with incomplete improvement of her neurological disorders and was registered on the waiting list for transplantation.

ENDOCRINE MANIFESTATIONS OF PRIMARY HYPEROXALURIA

OBJECTIVE

Primary hyperoxaluria type 1 (PH1) is a rare metabolic disorder of oxalate overproduction. It is associated with urolithiasis and nephrocalcinosis, which progress to end-stage renal disease and systemic oxalosis. As oxalate deposits in tissues, non-parathyroid hormone (nonPTH)-mediated hypercalcemia, oxalate osteopathy, primary hypothyroidism, and primary hypogonadism develop. In this review, we will present a case of PH1 and provide an overview of this clinical entity and its endocrine manifestations.

METHODS

We conducted a PubMed search for articles related to PH1. The terms "primary hyperoxaluria," "nonPTH mediated hypercalcemia," "hypothyroidism," and "hypogonadism" were used to identify pertinent literature.

RESULTS

Given the rarity of PH1, there is scant literature regarding the incidence and clinical significance of endocrine manifestations of this disorder. There are rare reports of hypercalcemia secondary to osteoclast-stimulating activity of macrophages in bone granulomas, which occur in response to oxalate deposits. We report that hypercalcemia may also be mediated by 1,25-dihydroxyvitamin D and PTH-related protein (PTHrP). Primary hypothyroidism and primary hypogonadism are thought to be due partly to calcium oxalate deposition in thyroid and testicular tissue. The presented case is the first to report PTHrP-mediated hypercalcemia and primary hypogonadism in a patient with PH1.

CONCLUSION

PH1 is a metabolic disease with significant morbidity and mortality. Owing to its rarity, it is not widely recognized in the field of endocrinology, despite presenting with several endocrinopathies. Recognition of endocrine disturbances can result in early and successful treatment, limiting morbidity and improving quality of life in these challenging patients.

ABBREVIATIONS

1,25(OH)₂D= 1,25-dihydoxyvitamin D AGT = alanine:glyoxylate aminotransferase ESRD = end-stage renal disease GRHPR = glyoxylate reductase-hydroxypyruvate reductase nonPTH = non-parathyroid hormone PH = primary hyperoxaluria pQCT = peripheral quantitative computed tomography PTH = parathyroid hormone PTHrP = parathyroid hormone-related protein T4 = thyroxine TSH = thyroid-stimulating hormone.

Experimental mould growth and mycotoxin diffusion in different food items

Isolates of Penicillium commune, Penicillium crustosum, Penicillium expansum, Penicillium roqueforti and Aspergillus versicolor, were inoculated on different food items (hard cheese, crème fraiche, tomato purée, apple and blueberry jam) and incubated at 15 °C for 14 days at 50% relative humidity (RH). After incubation the food samples were divided into 3 subsamples; A was 0-2 cm from the surface and including the fungal colony, subsample B was 2-4 cm and subsample C was the rest from >4 cm from the surface. The subsamples were analysed with a multianalyte method capable of identifying more than several hundreds of fungal metabolites. The outcome showed that mouldy food can contain a cocktail of bioactive secondary metabolites including mycotoxins and sometimes at high concentrations. Measurements of the diffusion of fungal metabolites from the colony on the surface (layer A) into the food (layer B and C) showed that the fungal metabolites do not diffuse more than 2 cm into the inner core of the hard cheese. On the other hand in more liquid foods, such as crème fraiche, fruit jams and tomato purée, the toxins diffused quite readily throughout the entire food sample. The levels of patulin found in the apple jam indicate that the tolerable daily intake for patulin may easily be exceeded even if the mouldy layer A is removed. This limited study calls for more similar studies to be performed to give risk managers a sound basis for advice to consumers.

Clinical spectrum of primary hyperoxaluria type 1: Experience of a tertiary center

BACKGROUND AND AIM

Primary hyperoxalurias are rare inborn errors of metabolism resulting in increased endogenous production of oxalate that leads to excessive urinary oxalate excretion. Diagnosis of primary hyperoxaluria type 1 (PH1) is a challenging issue and depends on diverse diagnostic tools including biochemical analysis of urine, stone analysis, renal biopsy, genetic studies and in some cases liver biopsy for enzyme assay. We characterized the clinical presentation as well as renal and extrarenal phenotypes in PH1 patients.

METHODS

This descriptive cohort study included patients with presumable PH1 presenting with nephrolithiasis and/or nephrocalcinosis (NC). Precise clinical characterization of renal phenotype as well as systemic involvement is reported. AGXT mutational analysis was performed to confirm the diagnosis of PH1.

RESULTS

The study cohort included 26 patients with presumable PH1 with male to female ratio of 1.4:1. The median age at time of diagnosis was 6 years, nevertheless the median age at initial symptoms was 3 years. Thirteen patients (50%) were diagnosed before the age of 5 years. Two patients had no symptoms and were diagnosed while screening siblings of index patients. Seventeen patients (65.4%) had reached end-stage renal disease (ESRD): 6/17 (35.3%) during infancy, 4/17 (23.5%) in early childhood and 7/17 (41.29%) in late childhood. Two patients (7.7%) had clinically manifest extra renal (retina, heart, bone, soft tissue) involvement. Mutational analysis of AGXT gene confirmed the diagnosis of PH1 in 15 out of 19 patients (79%) where analysis had been performed. Fifty percent of patients with maintained renal functions had projected 10 years renal survival.

CONCLUSION

PH1 is a heterogeneous disease with wide spectrum of clinical, imaging and functional presentation. More than two-thirds of patients presented prior to the age of 5 years; half of them with the stormy course of infantile PH1. ESRD was the commonest presenting manifestation in two-thirds of our cohort.