Primary hyperoxaluria: spectrum of clinical and imaging findings

Primary hyperoxaluria in adults and children: a nationwide cohort highlights a persistent diagnostic delay

Background

Primary hyperoxalurias (PH) are extremely rare genetic disorders characterized by clinical heterogeneity. Delay in diagnosing these conditions can have detrimental effects on patient outcomes. The primary objective of this study is to assess the current diagnostic delay for PH.

Methods

This nationwide, observational and retrospective study included patients who received a genetic diagnosis of PH types 1, 2 and 3 between 1 January 2015 and 31 December 2019. Diagnostic delay was defined as the duration between the onset of symptoms and the time of genetic diagnosis.

Results

A total of 52 patients (34 children and 18 adults) were included in the study, with 40 PH1 (77%), 3 PH2 (6%) and 9 PH3 (17%). At the time of diagnosis, 12 patients (23%) required dialysis. Among the PH1 patients, the predominant symptom at onset in adults was renal colic (79% of cases), whereas symptoms in children were more diverse (renal colic in 17% of cases). The diagnostic delay was significantly shorter in children compared with adults [median (interquartile range)]: 1.2 (0.1-3.0) versus 30 (17-36) years, respectively (P < .0001). RNA interference was utilized in 23 patients (58%). Five individuals (13%) underwent double liver-kidney transplantation, and five (13%) received isolated kidney transplantation, with lumasiran therapy in four patients. For PH2 and PH3 patients, the diagnostic delay ranges from 0 to 3 years, with renal colic as first symptom in 33% of cases.

Conclusion

This extensive and recent cohort of PH underscores the considerable delay in diagnosing PH, particularly in adults, even in a country with a dedicated organization for enhancing the overall management of rare diseases. These findings reinforce the imperative for increased awareness among relevant specialties regarding the evaluation of urolithiasis.

Nephrocalcinosis in Neonates

Nephrocalcinosis occurs in as many as 40% of preterm neonates. Many causes and contributors predispose neonates to develop nephrocalcinosis, including metabolic, genetic, and iatrogenic factors. Because nephrocalcinosis can be a manifestation of an underlying genetic disorder, neonates with nephrocalcinosis must undergo an evaluation to identify and address contributors, to prevent further renal calcium deposition that can potentially lead to renal dysfunction. In this article, we review the epidemiology, pathogenesis, diagnosis, and evaluation of nephrocalcinosis in neonates. We also summarize the natural history of nephrocalcinosis of prematurity as well as the management of this condition.

Late Presentation of Primary Oxalosis, Microcrystalline Arthropathy, and Tumoral Calcinosis: A Case Report and a Literature Review

BACKGROUND

Primary hyperoxaluria consists of a group of inherited disorders with enzymatic defects in the glyoxylate pathway, leading to decreased oxalate metabolism. The resulting oxalic deposition is specifically responsible for kidney disease and joint disease. Neonatal oxalosis is the most severe form of primary hyperoxia type 1, with the onset of end-stage renal disease in childhood.

CASE PRESENTATION

A 55-year-old hemodialysis man was referred to Nephrology because of inflammatory polyarthralgia and periarticular swelling evolving for six months. He had been on hemodialysis for six years for end-stage chronic renal failure, diagnosed at the same time as primary hyperoxaluria. Radiological investigation showed a rugby jersey appearance on the lumbar spine, budding calcium tone opacities next to large joints and clavicles, vascular calcifications and tumoral calcinosis. The synovial fluid contained a few cells with polymorphic intracellular crystals. We ruled out hyperparathyroidism, hypoparathyroidism, and related phosphocalcic disorders, and we retained arthropathy and tumoral calcinosis secondary to primary hyperoxaliuria. The patient also had congestive heart failure. Despite intensification of hemodialysis, he did not improve and died at the age of 56 in the context of cachexia.

CONCLUSION

This rare case documents the possible occurrence of late clinical presentation and long survival in primary oxalosis with extra renal complications.

The real world experience of pediatric primary hyperoxaluria patients in the PEDSnet clinical research network

The rarity of primary hyperoxaluria (PH) challenges our understanding of the disease. The purpose of our study was to describe the course of clinical care in a United States cohort of PH pediatric patients, highlighting health service utilization. We performed a retrospective cohort study of PH patients < 18 years old in the PEDSnet clinical research network from 2009 to 2021. Outcomes queried included diagnostic imaging and testing related to known organ involvement of PH, surgical and medical interventions specific to PH-related renal disease, and select PH-related hospital service utilization. Outcomes were evaluated relative to cohort entrance date (CED), defined as date of first PH-related diagnostic code. Thirty-three patients were identified: 23 with PH type 1; 4 with PH type 2; 6 with PH type 3. Median age at CED was 5.0 years (IQR 1.4, 9.3 years) with the majority being non-Hispanic white (73%) males (70%). Median follow-up between CED and most recent encounter was 5.1 years (IQR 1.2, 6.8). Nephrology and Urology were the most common specialties involved in care, with low utilization of other sub-specialties (12%-36%). Most patients (82%) had diagnostic imaging used to evaluate kidney stones; 11 (33%) had studies of extra-renal involvement. Stone surgery was performed in 15 (46%) patients. Four patients (12%) required dialysis, begun in all prior to CED; four patients required renal or renal/liver transplant.    Conclusion: In this large cohort of U.S. PH children, patients required heavy health care utilization with room for improvement in involving multi-disciplinary specialists. What is Known: • Primary hyperoxaluria (PH) is rare with significant implications on patient health. Typical involvement includes the kidneys; however, extra-renal manifestations occur. • Most large population studies describe clinical manifestations and involve registries. What is New: • We report the clinical journey, particularly related to diagnostic studies, interventions, multispecialty involvement, and hospital utilization, of a large cohort of PH pediatric patients in the PEDSnet clinical research network. • There are missed opportunities, particularly in that of specialty care, that could help in the diagnosis, treatment, and even prevention of known clinical manifestations.

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.

The Crystalline Nephropathies

Crystalline nephropathies are a unique form of kidney disease characterized by the histologic finding of intrarenal crystal deposition. The intrinsic nature of some molecules and ions combined with a favorable tubular fluid physiology leads to crystal precipitation and deposition within the tubular lumens. Crystal deposition promotes kidney injury through tubular obstruction and both direct and indirect cytotoxicities. Further kidney injury develops from inflammation triggered by these crystals. From a clinical standpoint, the crystalline nephropathies are associated with abnormal urinalysis and urinary sediment findings, tubulopathies, acute kidney injury (AKI), and/or chronic kidney disease (CKD). Urine sediment examination is often helpful in alerting clinicians to the possibility of crystal-related kidney injury. The identification of crystals within the kidneys on biopsy by pathologists prompts clinicians to evaluate patients for medication-related kidney injury, dysproteinemia-related malignancies, and certain inherited disorders. This review will focus on the clinical and pathologic aspects of these 3 categories of crystalline nephropathies.

The current status of preventive measures for urinary calculi in children

Urological calculus is a common disease in urology. Urological calculi are generally more common in adults but have become more common in children in recent years. Most existing studies focus on the prevention of urinary calculi in adults; there are relatively few articles on calculi in children. Reported preventive measures are not comprehensive enough, while the latest research progress has not been updated. The pathogenesis and preventive measures associated with urinary calculi have been the focus of research, but many preventive measures still need further clarification. This article reviews the progress on preventive measures for urinary calculi in children.

Characteristics of the genotype and phenotype in Chinese primary hyperoxaluria type 1 populations

The aim of our study is to explore the relationship between genotype and phenotype in Chinese PH1 patients and determine the putative mutation hotspot regions. This was a retrospective study regarding 13 Chinese PH1 patients. And all sporadic published researches of Chinese PH1 populations were searched and enrolled based on the inclusive standard. All patients presented with multiple urolithiasis or nephrolithiasis. Urinary oxalate values demonstrated an obvious and extensive variability, ranging from 1.01 to 3.85 mmol/1.73 m². Molecular diagnosis showed that 13 mutant types were detected. Infantile form patient (pt.) 10 and five patients (pts. 5, 7, 8, 9, 12) carrying c.815_816insGA or c.33_34insC demonstrated a worse prognosis, of whom pt. 5 progressed into ESRD 4 years later and died of chronic kidney failure. Based on the integrated Chinese mutation data, two variants (c.815_816insGA and c.33_34insC) were determined as the most common mutations. Besides, c.1049G>A was initially identified in a Chinese patient. Conclusions: heterogeneity between genotype and phenotype was observed and described in Chinese PH1 patients. c.815_816insGA and c.33_34insC which were recognized as AGXT mutation hotspot regions in China implied a poor prognosis. And c.1049G>A was not determined as the race-specific mutation of Pakistani.

Nephrocalcinosis: A Review of Monogenic Causes and Insights They Provide into This Heterogeneous Condition

The abnormal deposition of calcium within renal parenchyma, termed nephrocalcinosis, frequently occurs as a result of impaired renal calcium handling. It is closely associated with renal stone formation (nephrolithiasis) as elevated urinary calcium levels (hypercalciuria) are a key common pathological feature underlying these clinical presentations. Although monogenic causes of nephrocalcinosis and nephrolithiasis are rare, they account for a significant disease burden with many patients developing chronic or end-stage renal disease. Identifying underlying genetic mutations in hereditary cases of nephrocalcinosis has provided valuable insights into renal tubulopathies that include hypercalciuria within their varied phenotypes. Genotypes affecting other enzyme pathways, including vitamin D metabolism and hepatic glyoxylate metabolism, are also associated with nephrocalcinosis. As the availability of genetic testing becomes widespread, we cannot be imprecise in our approach to nephrocalcinosis. Monogenic causes of nephrocalcinosis account for a broad range of phenotypes. In cases such as Dent disease, supportive therapies are limited, and early renal replacement therapies are necessitated. In cases such as renal tubular acidosis, a good renal prognosis can be expected providing effective treatment is implemented. It is imperative we adopt a precision-medicine approach to ensure patients and their families receive prompt diagnosis, effective, tailored treatment and accurate prognostic information.

Oxalate deposition in renal allograft biopsies within 3 months after transplantation is associated with allograft dysfunction

BACKGROUND

Calcium oxalate (CaOx) deposition in the kidney may lead to loss of native renal function but little is known about the prevalence and role of CaOx deposition in transplanted kidneys.

METHODS

In patients transplanted in 2014 and 2015, all for-cause renal allograft biopsies obtained within 3 months post-transplantation were retrospectively investigated for CaOx deposition. Additionally, all preimplantation renal biopsies obtained in 2000 and 2001 were studied.

RESULTS

In 2014 and 2015, 388 patients were transplanted, of whom 149 had at least one for-cause renal biopsy. Twenty-six (17%) patients had CaOx deposition. In the population with CaOx deposition: Patients had significantly more often been treated with dialysis before transplantation (89 vs. 64%; p = 0.011); delayed graft function occurred more frequently (42 vs. 23%; p = 0.038); and the eGFR at the time of first biopsy was significantly worse (21 vs. 29 ml/min/1.73m2; p = 0.037). In a multivariate logistic regression analysis, eGFR at the time of first biopsy (OR 0.958, 95%-Cl: 0.924-0.993, p = 0.019), dialysis before transplantation (OR 4.868, 95%-Cl: 1.128-21.003, p = 0.034) and the time of first biopsy after transplantation (OR 1.037, 95%-Cl: 1.013-1.062, p = 0.002) were independently associated with CaOx deposition. Graft survival censored for death was significantly worse in patients with CaOx deposition (p = 0.018). In only 1 of 106 preimplantation biopsies CaOx deposition was found (0.94%).

CONCLUSION

CaOx deposition appears to be primarily recipient-derived and is frequently observed in for-cause renal allograft biopsies obtained within 3 months post-transplantation. It is associated with inferior renal function at the time of biopsy and worse graft survival.

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.

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.