Dent's disease and prevalence of renal stones in dialysis patients in Northeastern Italy

Dent's Disease: A Cause of Monogenic Kidney Stones and Nephrocalcinosis

Kidney stones are becoming increasingly common, affecting up to 10% of adults. A small percentage are of monogenic origin, such as Dent's disease (DD). DD is a syndrome that causes low-molecular-weight proteinuria, hypercalciuria, nephrolithiasis, and nephrocalcinosis. It is X-linked, and most patients have mutations in the CLCN5 gene. We performed a review of the literature and evaluated the case series (n = 6) of a single center in Spain, reviewing the natural evolution of kidney stones, clinical implications, laboratory analyses, radiological development, and treatment. All patients had a genetically confirmed diagnosis, with the CLCN5 mutation being the most frequent (66%). All patients had proteinuria and albuminuria, while only two and three presented hypercalciuria and phosphate abnormalities, respectively. Only one patient did not develop lithiasis, with most (60%) requiring extracorporeal shock wave lithotripsy or surgery during follow-up. Most of the patients are under nephrological follow-up, and two have either received a renal transplant or are awaiting one. The management of these patients is similar to that with lithiasis of non-monogenic origin, with the difference that early genetic diagnosis can help avoid unnecessary treatments, genetic counseling can be provided, and some monogenic kidney stones may benefit from targeted treatments.

Diagnostic policies on nephrolithiasis/nephrocalcinosis of possible genetic origin by Italian nephrologists: a survey by the Italian Society of Nephrology with an emphasis on primary hyperoxaluria

BACKGROUND

Primary hyperoxaluria is a genetic disorder of the metabolism of glyoxylate, the precursor of oxalate. It is characterized by high endogenous production and excessive urinary excretion of oxalate, resulting in the development of calcium oxalate nephrolithiasis, nephrocalcinosis, and, in severe cases, end-stage kidney disease and systemic oxalosis. Three different forms of primary hyperoxaluria are currently known, each characterized by a specific enzymatic defect: type 1 (PH1), type 2 (PH2), and type 3 (PH3). According to currently available epidemiological data, PH1 is by far the most common form (about 80% of cases), and is caused by a deficiency of the hepatic enzyme alanine:glyoxylate aminotransferase.

METHODS

A survey on rare forms of nephrolithiasis and nephrocalcinosis with a focus on primary hyperoxaluria in the setting of Italian Nephrology and Dialysis Centers, using an online questionnaire, was recently conducted by the Project Group "Rare Forms of Nephrolithiasis and Nephrocalcinosis" of the Italian Society of Nephrology, with the aim of assessing the impact and management of this disorder in clinical practice in Italy.

RESULTS

Forty-five public and private Italian Centers participated in the survey, and responses to the questionnaire were provided by 54 medical professionals. The survey results indicate that 21 out of the 45 participating Centers are managing or have managed primary hyperoxaluria patients, most of whom are on dialysis, or are recipients of kidney transplants.

CONCLUSIONS

The data of this survey indicate the need to implement genetic testing in suspected cases of primary hyperoxaluria, not only in the setting of dialysis or transplantation, but also with the aim of encouraging early diagnosis of PH1, which is the only type of primary hyperoxaluria for which specific drug therapy is currently available.

Nephrolithiasis, stone composition, meteorology, and seasons in Malta: Is there any connection?

CONTEXT

The effect of seasons and meteorology on the incidence of nephrolithiasis has been studied in various regions around the globe, but seldom in the Mediterranean.

AIMS

This retrospective analysis aims at investigating these putative effects in the Maltese Islands, whose climate is typically Mediterranean, followed by a systematic review of the literature.

MATERIALS AND METHODS

Submission rate and chemical composition of all kidney stones after spontaneous passage or surgical removal between January 2009 and December 2011 were analyzed according to seasons and corresponding meteorology.

RESULTS

A total of 389 stones were analyzed. A higher stone submission rate was observed in summer compared to winter (31.6% vs. 20.8%, P = 0.0008) and in the warm period compared to the cold period (57.1% vs. 42.9%, P = 0.0001). Significant correlation was established between the monthly number of stones and mean monthly maximum temperature (r = 0.50, P = 0.002), mean monthly temperature (r = 0.49, P = 0.003) and mean monthly Humidex (r = 0.49, P = 0.007). Humidex was found to be an independent predictor for stone submission (β = 0.49, P = 0.007). The majority of stones contained calcium (83.3%), combined with oxalate (77.6%), phosphate (14.7%), and carbonate (2.8%). Some stones (11.8%) contained a mixture of >1 negatively charged molecules. Urate (11.6%), cysteine (4.6%), and ammonium-magnesium-phosphate (0.5%) constituted the rest. There was no association between chemical composition and seasons. Literature review included 25 articles. Higher ambient temperature and warm seasons were the most commonly encountered risk factors for both presentation and etiology of nephrolithiasis.

CONCLUSIONS

A significant positive correlation was noted between ambient temperature and stone submission rate, which was significantly higher during the warm months in Malta.

When to suspect a genetic disorder in a patient with renal stones, and why

Nephrolithiasis is a common disorder, with a rising prevalence in the general population. Its pathogenesis is still unclear, but a role for genetics has long been recognized, especially in cases of the more common calcium nephrolithiasis. Although relatively rare, monogenic causes of hypercalciuria and nephrolithiasis do exist and their timely recognition is important from a prognostic and therapeutic viewpoint. This article reviews the clinical and laboratory findings characterizing inherited causes of nephrolithiasis with a view to helping clinicians to recognize and manage these rare conditions.

Impact of stone disease: chronic kidney disease and quality of life

This article reviews the impact of stone disease on chronic kidney disease and renal function; evaluating the natural progression of disease as well as the impact of surgical interventions. The impact of stone disease, medical therapy, and surgical therapy for stones on quality of life is discussed.

Urolithiasis and the risk of ESRD

BACKGROUND AND OBJECTIVES

The contribution of urolithiasis, if any, to the development of ESRD is unclear.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

All stone formers in Olmsted County, Minnesota, first diagnosed between 1984 and 2008 were identified by diagnostic codes with up to four controls matched on age and sex. Charts were reviewed to validate symptomatic stone formers in a random subset. Incident ESRD events were identified by the US Renal Data System.

RESULTS

Altogether, 51 stone formers and 75 controls developed ESRD among 6926 stone formers and 24,620 matched controls followed for a mean of 9 years. Stone formers had an increased risk of ESRD after adjusting for diabetes, hypertension, dyslipidemia, gout, and CKD (hazard ratio: 2.09; 95% confidence interval: 1.45-3.01). This increased risk of ESRD remained in the subset of 2457 validated symptomatic stone formers (hazard ratio: 1.95; 95% confidence interval: 1.09-3.49). The attributable risk of ESRD from symptomatic urolithiasis was 5.1% based on a prevalence of 5.4% for stone formers. For stone formers versus controls who developed ESRD, there was an increased likelihood of past hydronephrosis (44% versus 4%), recurrent urinary tract infections (26% versus 4%), acquired single kidney (15% versus 3%), neurogenic bladder (12% versus 1%), and ileal conduit (9% versus 0%), but not diabetes (32% versus 49%) or hypertension (44% versus 52%).

CONCLUSIONS

Symptomatic stone formers are at increased risk for ESRD independent of several cardiovascular risk factors. Other urological disease is relatively common among stone formers who develop ESRD.

Chronic kidney disease in kidney stone formers

Recent population studies have found symptomatic kidney stone formers to be at increased risk for chronic kidney disease (CKD). Although kidney stones are not commonly identified as the primary cause of ESRD, they still may be important contributing factors. Paradoxically, CKD can be protective against forming kidney stones because of the substantial reduction in urine calcium excretion. Among stone formers, those with rare hereditary diseases (cystinuria, primary hyperoxaluria, Dent disease, and 2,8 dihydroxyadenine stones), recurrent urinary tract infections, struvite stones, hypertension, and diabetes seem to be at highest risk for CKD. The primary mechanism for CKD from kidney stones is usually attributed to an obstructive uropathy or pyelonephritis, but crystal plugs at the ducts of Bellini and parenchymal injury from shockwave lithotripsy may also contribute. The historical shift to less invasive surgical management of kidney stones has likely had a beneficial impact on the risk for CKD. Among potential kidney donors, past symptomatic kidney stones but not radiographic stones found on computed tomography scans were associated with albuminuria. Kidney stones detected by ultrasound screening have also been associated with CKD in the general population. Further studies that better classify CKD, better characterize stone formers, more thoroughly address potential confounding by comorbidities, and have active instead of passive follow-up to avoid detection bias are needed.

Dent's disease: clinical features and molecular basis

Dent's disease is an X-linked recessive renal tubulopathy characterized by low-molecular-weight proteinuria (LMWP), hypercalciuria, nephrocalcinosis, nephrolithiasis, and progressive renal failure. LMWP is the most constant feature, while the other clinical manifestations show wide variability. Patients also present variable manifestations of proximal tubule dysfunctions, such as aminoaciduria, glucosuria, hyperphosphaturia, kaliuresis, and uricosuria, consistent with renal Fanconi syndrome. Dent's disease affects mainly male children, and female carriers are generally asymptomatic. In two-thirds of patients, the disease is caused by mutations in the CLCN5 gene, which encodes the electrogenic chloride/proton exchanger ClC-5. A few patients have mutations in OCRL1, the gene associated with the oculocerebrorenal syndrome of Lowe, which encodes a phosphatidylinositol-4,5-biphosphate-5-phosphatase (OCRL1). Both ClC-5 and OCRL1 are involved in the endocytic pathway for reabsorption of LMW proteins in the proximal tubule. This review will provide an overview of the important phenotypic characteristics of Dent's disease and summarize the molecular data that have significantly increased our comprehension of the mechanisms causing this disease.

Phenotypic and genetic heterogeneity in Dent's disease--the results of an Italian collaborative study

BACKGROUND

Dent's disease is an inherited tubulopathy caused by CLCN5 gene mutations. While a typical phenotype characterized by low-molecular-weight (LMW) proteinuria, hypercalciuria, nephrocalcinosis, nephrolithiasis, rickets and progressive renal failure in various combinations often enables a clinical diagnosis, less severe sub-clinical cases may go under-diagnosed.

METHODS

By single-strand conformation polymorphism analysis and direct sequencing, we screened 40 male patients from 40 unrelated families for CLCN5 gene mutations. Twenty-four of these patients had the prominent features of Dent's disease, including LMW proteinuria, hypercalciuria and nephrocalcinosis.

RESULTS

We identified 24 mutations in the CLCN5 gene in 21/24 patients with a typical phenotype and in 3/16 patients with a partial clinical picture of Dent's disease. Overall, 10 novel CLCN5 mutations were identified (E6fsX11, W58fsX97, 267 del E, Y272C, N340K, F444fsX448, W547X, Q600X, IVS3 +2 G>C and IVS3 -1 G>A), extending the number of mutations identified so far from 75 to 85. The CLCN5 coding sequence was normal in three patients. In the group with an incomplete Dent's disease phenotype, we detected two intronic mutations and one silent substitution leading to the up regulation of an alternatively spliced isoform.

CONCLUSIONS

Our data confirm the genetic heterogeneity of Dent's disease. In most classic cases, the clinical diagnosis is confirmed by genetic tests.

Family history may be misleading in the diagnosis of Dent’s disease

The rare Dent's disease manifests with medullary nephrocalcinosis, nephrolithiasis, hypercalciuria, low molecular weight proteinuria and other tubular dysfunctions, rickets or osteomalacia, and renal failure, in various combinations. It is a recessive X-linked condition. Clinicians consider family history a fundamental pointer to its diagnosis, but this is not invariably the case as clearly pointed out by the two reported cases.