Risks and Benefits of Postoperative Double-J Stent Placement After Ureteroscopy: Results from the Clinical Research Office of Endourological Society Ureteroscopy Global Study

PURPOSE

Double-J stent placement after stone removal by ureteroscopy (URS) is common and recommended in many cases but debatable in others. In this study, the risks and benefits of postoperative Double-J stent placement in URS stone treatment procedures undertaken in current clinical practice are examined.

MATERIALS AND METHODS

The Clinical Research Office of Endourological Society (CROES) URS is a prospective, observational, international multicenter study, in which patients are candidates for URS as primary treatment or after failure of prior treatment for ureteral and renal stones. Baseline, intraoperative, and postoperative data were collected. Predictors and outcomes of postoperative stent placement were analyzed by inverse probability-weighted regression adjustment of the relationship between a Double-J stent placement and outcomes (complications, readmission [including retreatment], and length of hospital stay).

RESULTS

Significant predictors of postoperative Double-J stent placement in URS treatment of ureteral stones were intraoperative complications, impacted stones, operation time, stone burden, age, presence of a solitary kidney, and stone-free rate. In renal stone treatment, the predictors identified included operation time, age, preoperative stent placement, anticoagulant use, presence of a solitary kidney, and intraoperative complications. In both ureteral and renal stone treatment groups, postoperative placement of a Double-J stent resulted in significantly fewer postoperative complications (p < 0.001) compared with patients who did not receive a stent.

CONCLUSIONS

Patient- and procedure-related variables were identified, which may enable an individualized approach to postoperative stenting, resulting in improved clinical outcomes in urologic stone treatment by URS.

Renal bone metaplasia: an incidental negligible finding or a disease to treat?

Renal bone metaplasia (RBM) is a uncommon condition and is often an incidental finding. The pathogenesis of this phenomenon is not clearly understood. The radiological signs described are not always present and the diagnosis is challenging. In the literature, there is no any conclusion about the optimal management of this condition due to the absence of some conclusions regarding its etiology. In our opinion, no treatment should be applied to prevent its possible evolution into urolithiasis. Surgical removal of the RBM is an overtreatment for a phenomenon not understood and potentially insignificant. We report our experience with a watchful waiting approach in a case of incidental diagnosis of RBM. After 3 years, the patient is asymptomatic, with no evidence of malignancies evolution, new renal stones or growth of the residual RBM.

Percutaneous nephrolithotomy in children in different age groups: data from the Clinical Research Office of the Endourological Society (CROES) Percutaneous Nephrolithotomy Global Study

OBJECTIVES

To present the overall results of paediatric percutaneous nephrolithotomy (PCNL) compared with adults. To present the indications, complications and outcomes of patients treated in the participating centres in the PCNL Global Study, as categorised in different age groups.

PATIENTS AND METHODS

The Clinical Research Office of the Endourological Society (CROES) Study was conducted from November 2007 to December 2009, and included 96 centres and >5800 patients. All children aged ≤14 years in the PCNL Global Study database were the focus of the study.

RESULTS

In all, 107 children aged ≤14 years were included in the analysis. The PCNL procedure was conducted in 13 patients (12.1%) in the supine position; tubeless PCNL was performed in 15 patients (14%); and balloon dilatation was preferred in 22 patients (20.5%). The overall mean operative duration was 97.02 min; blood transfusion rate, fever and stone-free rates were 9%, 14% and 70.1%, respectively. A comparison of the paediatric PCNL cases according to age groups showed no statistically significant differences between the subgroups for patient characteristics, co-morbidities, renal anomalies, or previous surgical history. In the evaluation of the operative details, the mean sheath size and nephrostomy tube size were larger in school-age children than the preschool children (P = 0.01 and 0.002, respectively). There was a difference in the preferred methods for confirming stone-free status, with ultrasonography preferred more in preschool children (P < 0.001). The PCNL procedure position, puncture site, dilatation method, postoperative tube application, and surgical outcomes were comparable in school- and preschool-age children. While operative details showed some differences between children and adults, the surgical outcomes were comparable.

CONCLUSIONS

A considerable number (45.7%) of the paediatric patients had a previous history of stone intervention. Based on the findings of the present study, we can suggest that PCNL can be applied safely and effectively in children in different age groups. Outcomes appear comparable with those in adults for the success and complication rates, in the presence of substantial indications, appropriate equipment and adequate experience.

Percutaneous ultrasound-guided radiofrequency ablation of an allograft renal cell carcinoma: a case report

BACKGROUND

Renal cell carcinomas (RCCs) are rarely described in transplanted kidneys. Available therapeutic strategies range from allograft nephrectomy to nephron-sparing procedures such as partial nephrectomy or image-guided thermal ablation. Percutaneous radiofrequency ablation (RFA) is a minimally invasive technique which provides promising oncologic outcomes in small allograft RCCs while preserving allograft function. So far, only a few cases have been reported in the transplant setting. We describe a renal transplant RCC successfully approached by ultrasound-guided RFA.

METHODS

A 42-year-old renal transplant recipient developed a small subcapsular allograft RCC at 11 years after transplantation. The decline in glomerular filtration rare prompted us to preserve as much parenchyma as possible. Ultrasound-guided RFA was performed under light sedation and local analgesia in a single session with a Starbust Talon needle.

RESULTS

Postablation contrast-enhanced ultrasound displayed a 25×23 mm avascular area of complete necrosis. After 3 months gadolinium-enhanced magnetic resonance imaging confirmed the absence of viable tumor tissue and while the patient did not experience any graft function reduction (serum creatinine 2.6 mg/dL).

CONCLUSIONS

Image-guided RFA represents a promising therapeutic modality for small allograft RCCs in recipients with mild graft dysfunction and/or elevated surgical risk. It is associated with low morbidity and parenchymal preservation.

Benzene metabolites inhibit the release of proinflammatory mediators and cytokines from human basophils

Benzene and its metabolites have been involved in the pathogenesis of chronic lung inflammation and allergic disorders such as bronchial asthma. However, the effects of these xenobiotics on human basophils, key cells in the development of respiratory allergy, have not been investigated. We examined the effects of hydroquinone (HQ) and benzoquinone (BQ), two important chemicals implicated in benzene toxicity, on the release of preformed (histamine) and de novo synthesized mediators (cysteinyl leukotriene C4, LTC4, and IL-4) from human basophils. Preincubation of basophils purified from normal donors with HQ (3-100 microM) inhibited up to 30% histamine release induced by anti-IgE and up to 55% of that induced by the Ca2+ ionophore A23187. HQ had no effect on histamine release induced by formyl-methionyl-leucyl-phenylalanine (f-Met-Leu-Phe). Preincubation of basophils with BQ (3-100 microM) resulted in the concentration-dependent inhibition of histamine release (up to 70%) induced by anti-IgE, A23187 and f-Met-Leu-Phe. HQ completely suppressed the de novo synthesis of LTC4 from basophils challenged with anti-IgE or f-Met-Leu-Phe and the production of IL-4 in cells stimulated with anti-IgE. These results indicate that two major benzene metabolites, HQ and BQ, inhibit the release of proinflammatory mediators and Th2-promoting cytokines from basophils activated by different stimuli. These results suggest that benzene metabolites interfere with multiple intracellular signals involved in the activation of human basophils.

[Percutaneous nephrolithotomy (PCNL) in a 9-year-old patient with horseshoe kidney]

INTRODUCTION

The horseshoe kidney is the most frequent renal anomaly, with a prevalence of 0.25% and a male to female ratio of 3:1. Although the pathogenesis remains controversial, the consequences of the impaired urinary drainage are well known: up to two third of patients present with urinary stasis, infection and urolithiasis. Percutaneous nephrolithotomy (PCNL) is a successful procedure for urolithiasis in horseshoe kidneys.

MATERIALS AND METHODS

A 9-year-old patient with a 4-cm stone associated with horseshoe kidney underwent Percutaneous nephrolithotomy (PCNL). During the procedure, a flexible uretheroscopy was performed in order to obtain a complete vision and an optimal management of the procedure.

RESULTS

At the end of the procedure, the patient was stone-free. We reported no hemorrhagic complications, no pain and no infection. The patient was discharged after 48 hours.

CONCLUSIONS

The procedure is safe and effective, as long as the surgeon pays attention to the recommendations below.

Percutaneous Nephrolithotomy (PCNL) in a 9-year-old Patient with Horseshoe Kidney

Introduction

The horseshoe kidney is the most frequent renal anomaly, with a prevalence of 0.25% and amale to female ratio of 3:1. Although the pathogenesis remains controversial, the consequences of the impaired urinary drainage are well known: up to two third of patients present with urinary stasis, infection and urolithiasis. Percutaneous nephrolithotomy (PCNL) is a successful procedure for urolithiasis in horseshoe kidneys.

Materials and Methods

A 9-year-old patient with a 4-cm stone associated with horseshoe kidney underwent Percutaneous nephrolithotomy (PCNL). During the procedure, a flexible uretheroscopy was performed in order to obtain a complete vision and an optimal management of the procedure.

Results

At the end of the procedure, the patient was stone-free. We reported no hemorrhagic complications, no pain and no infection. The patient was discharged after 48 hours.

Conclusions

The procedure is safe and effective, as long as the surgeon pays attention to the recommendations below.

Percutaneous nephrolithotripsy (PCNL) in children: experience of Parma

19 Percutaneous nephrolithotripsy procedures were done in 15 children aged from 8 months to 16 years with complex renal stones and/or extracorporeal shock wave lithotripsy refractory stones. The percutaneous techniques were done with the instrument and position (prone and supine) used in adults. 14/15 patients were stone-free (13 pts in one time, 1 pt in 2 procedures and 1 pt, with complex bilateral stones disease, in 5 endourological sessions). No relevant complications developed: 1 patient need a blood transfusion and 1 a temporary Indwelling catheter for colic pain due to oedema. We believe that in children the endourological approach is better than traditional open surgery or reiterated extracorporeal shock wave lithotripsy sessions which often need anaesthesia and can not guarantee a complete clearance of the stones.

Vanilloid-mediated apoptosis in prostate cancer cells through a TRPV-1 dependent and a TRPV-1-independent mechanism

Vanilloids are natural molecules identified in a plethora of foods normally ingested through the diet. They mediate apoptosis through a direct pathway (independent of TRPV-1, the receptor for vanilloids) and through an indirect pathway, i.e., thanks to the interaction with TRPV-1 and the successive intracellular calcium growth [Ca2+]i. Some vanilloids, such as capsaicin, dihydrocapsaicin and resiniferatoxin (the ultrapotent analogue of capsaicin, extractable from Euphorbia resinifera), may be considered as coenzyme Qantagonists: in fact, they inhibit the run of the electrons through the electron transport chain, so determining an excess of reactive oxygen species (ROS). A second effect of the interaction between the vanilloids and TRPV-1 receptor may be reported: it is the fast decrease of the transmembrane mitochondrial potential (delta psi m). Through the direct pathway, on the contrary, the vanilloids induce apoptosis also interacting with caspases, particularly caspase 1 and 3. On the whole, the vanilloids are able to lead to the intracellular calcium growth and consequently to the evidence of precocious and late elements of apoptosis.

High Intensity Focused Ultrasound (HIFU): a useful alternative choice in prostate cancer treatment. Preliminary results

INTRODUCTION AND AIMS

High-Intensity Focused Ultrasound (HIFU) represents an alternative choice in mini-invasive treatment of prostate cancer. The technology of the device used to perform the treatment allows to exactly destroy a pre-selected area and to save all the tissues around it. We report our experience on the effectiveness and complications of this tecnique.

MATERIALS AND METHODS

From May 2006 to April 2007, 25 patients with prostate cancer were treated through Ablatherm (EDAP France) in spinal anesthesia. In the first six patients HIFU and TUR-P (Trans-Urethral Resection of Prostate) were performed in the same session and a suprapubic catheter was placed. In the other 14 patients HIFU was afterwards performed. In these patients a trans-urethral catheter was placed. All patients were divided into three groups: low risk (17 patients), intermediate risk (6 patients) and high risk (2 patients). The follow-up consisted in PSA evaluation after 1, 3, 6, 9, 12 months and in transrectal biopsy after six months. Complications related to the treatment, and symptomatological and sexual life tests were evaluated before and after the treatment.

RESULTS

HIFU overall success rate was 84% (biochemical relapses in only 4 patients out of 25). Success rate was represented as follows: 94.2% in the low risk group, 83.4% in the intermediate risk group and 0% in the high risk group. No complications occurred during the treatment nor in the immediately post-operative time.

CONCLUSIONS

We demonstrated that HIFU represents a useful alternative choice in mini-invasive therapy of prostate cancer. Particularly, results are remarkable in localized (low-intermediate risk) and low morbility prostate cancer. The role of this procedure in high risk patients needs to be further evaluated. Transrectal HIFU represents a mini-invasive therapeutic option that makes the treatment of prostate cancer possible in 84% of cases. Our results agree with the literature data and demonstrate that the success of the procedure depends on the correct indication of treatment and is strictly related to progression risk parameters.

Endourological Management of Ureteral Stenosis and Vesicoureteral Reflux after Renal Transplantation

Introduction and Objectives

Ureteral stenosis and vesicocoureteral reflux after renal transplantation represent a key concern because of their incidence and the associated morbidity. Prompt diagnosis and minimally invasive treatment are mandatory in immunosuppressed patients with single kidney. The aim of this study is to evaluate the success rate of the endourological techniques in the management of such complications.

Materials and Methods

Between January 1996 and December 2006, 647 kidney transplants were performed. Urinary tract continuity was re-established by ureteroneocystostomy according to Gregoir-Lich technique. We observed 13 cases of ureteral stenosis (2%) and 11 cases of symptomatic vesicoureteric reflux (1.7%). The endourogical procedure was performed in 13 patients: 5 cases of II-III grade vesicoureteric reflux, 4 early ureteral stenosis and 4 late ureteral stenosis. Patients with vesicoureteric reflux underwent endoscopic injection of macroplastique in 4 cases and Durasphere in 1. Early ureteral stenoses were treated using balloon dilation in 2 cases, balloon dilation and laser endoureterotomy in 3, ureteral stent placement in the other. Recipients with late stenosis underwent laser incision and balloon dilation in 2 cases, balloon dilation in 1 and a laser incision only in the last case. Combined antegrade and retrograde endoscopic approach was performed in 7 patients, whereas retrograde access in 1.

Results

Endourologic treatment was successful in 9 cases (69.2%); 2 patients required open reconstructive surgery due to endourological technique failure (early ureteropelvic junction stricture, late ureterovesical anastomotic stricture). Vesicoureteric reflux was corrected in 3 patients (60%), 2 patients underwent uretero-ureterostomy for recurrent reflux. No technique-related morbidity was observed. With a mean follow-up of 81.6 months, 8 patients show normal renal function, 5 patients have returned to haemodialysis (4 for chronic rejection, 1 for carcinoma in the graft).

Conclusions

Considering their low morbidity and the satisfactory success rate, we claim that endourological procedures should be considered the preferred treatment for ureteral stenosis and vesicoureteric reflux in selected patients.

Sister Chromatid Exchange and Oxidative DNA Damage in Paving Workers exposed to PAHs

Paving workers are exposed during road paving to several polycyclic aromatic hydrocarbons (PAHs) contained in asphalt fumes. In this study early genotoxic and oxidative effects of exposure to bitumen fumes were evaluated in 19 paving workers and 22 controls. Environmental and biological monitoring of exposure was carried out, measuring, on personal air samples from exposed workers collected during three working days, the concentration of 14 PAHs and urinary OH-pyrene at the end of each of the three working days. Genotoxic effect was evaluated analysing sister chromatid exchange (SCE) frequency and direct-oxidative DNA damage by formamido-pyrimidine-glycosylase (Fpg)-modified comet assay on lymphocytes. Tail moment values from Fpg-enzyme treated cells (TMenz) and from untreated cells (TM) were used as parameters of direct and oxidative DNA damage, respectively. For each subject, the TMenz/TM ratio >2.0 was used to indicate the presence of oxidative damage. DNA damage was also evaluated analysing comet percentage. Personal air samples showed low level of total PAHs (2.843 microg m(-3)) with prevalence of 2-3 ring PAHs (2.693 microg m(-3)). Urinary OH-pyrene after work-shift of the three working days was significantly higher than that found at the beginning of the working week. SCE analysis did not show any difference between two groups while an oxidative DNA damage was found in 37% of exposed with respect to the absence in controls. Comet percentage was significantly higher (P = 0.000 ANOVA) in the exposed than in controls. The results demonstrate the high sensitivity of comet assay to assess early oxidative effects induced by exposure to bitumen fumes at low doses and confirm the suitability of urinary OH-pyrene as a biomarker of PAH exposure. In conclusion the study suggests the use of Fpg-modified comet test as a biomarker of early genotoxic effects and that of urinary OH-pyrene as a biomarker of PAH exposure to furnish indications in terms of characterization, prevention and management of risk in occupational exposure to mixtures of potentially carcinogenic substances.

Ureteral hemangioma: a clinical case report

The most greater part of the tumors ureteralis are of malignant nature, they are verified especially in the elderly patient and they have a preference for the distal third of the ureter. Of the tumors benign ureteral, the emangioma is a very rare vascular neoplasm. The symptoms aspecificis of presentation are: hematuria, colic type pains, hydronephrosis and bladder inflammation. Thanks to the refinement of the radiological techniques (Urography, CTscan and eventually the ascending pyelography) and also to the simultaneous aid of the anatomopathologist, it is possible to obtain an accurate description of this pathology in a precocious stage in order to carry out a conservative approach. The peculiarity of the clinical case from us described depends on the fact that it deals with an occasional find, reaches our observation for appearance of severe hydronephrosis caused by ureteral stones, resolved him with methodic endoscopic.

[Study of genotoxic and oxidative effects induced by PAH exposure in paving workers]

Paving workers are exposed during road paving to several PAHs contained in asphalt fumes. We aimed to evaluate early genotoxic and oxidative effects in 19 paving workers and 22 controls. We analysed sister chromatide exchange (SCE) frequency as marker of genotoxicity. Moreover we assessed oxidative DNA damage by Fpg-modified comet assay on lymphocytes calculating tail moment values from fpg-enzyme treated cells (TMenz) and from untreated cells (TM). For each subject the TMenz/TM ratio higher than 2.0 was used to indicate the presence of oxidative damage. We also evaluated DNA damage analysing comet percentage. SCE analysis didn't show any difference between exposed and control groups. We found oxidative DNA damage in 37% of exposed in respect to the absence in controls. Comet percentage was significantly higher in the exposed than in controls. The results demonstrate the high sensitivity of comet assay to assess early oxidative effects induced by exposure to PAH mixtures at low doses and suggest the use of this biomarker in the characterization, prevention and management of risk induced by occupational exposure to mixtures of potentially carcinogenic substances.

Randomized comparison of loops for transurethral resection of the prostate: preliminary results

PURPOSE

To evaluate the comparative efficacy and morbidity of standard transurethral resection of prostate (TURP) and transurethral vaporesection (TUVRP) using four types of loops.

PATIENTS AND METHODS

In a one-to-one randomized study, 50 patients with lower urinary-tract symptoms suggestive of bladder outlet obstruction and benign prostatic enlargement underwent TURP. Clinical data were collected using digital rectal examination, transrectal ultrasonography for evaluation of prostate volume, IPSS and IIEF-5 questionnaires, and serum prostate specific antigen concentrations. Intraoperative blood loss and fluid absorption were evaluated by measuring serum hemoglobin and respiratory alcohol concentration. Patients were followed at 3 and 18 months with evaluation of clinical symptoms, flow rates, residual urine volumes, and complications.

RESULTS

There were no significant differences in blood loss, intraoperative fluid absorption, procedure time, or weight of the resected tissue between standard TURP and TUVRP with the various loops. No significant complications (infections, urethral stricture, reintervention) were seen.

CONCLUSIONS

In this comparison of the clinical outcome and morbidity of standard TURP versus different loops for TUVRP, there were no significant differences in any of the parameters evaluated.

Association between a polymorphism affecting an AP1 binding site in the promoter of the TCIRG1 gene and bone mass in women

The TCIRG1 gene encodes a component of the osteoclast vacuolar proton pump and previous work has shown that inactivating mutations of the TCIRG1 cause autosomal recessive osteopetrosis. In order to determine whether allelic variation in TCIRG1 contributes to the regulation of bone mineral density (BMD) in normal individuals, we studied the relationship between polymorphisms of TCIRG1 and BMD in a population-based cohort of 739 perimenopausal women. Five common polymorphisms were identified: two in the promoter, a conservative change within exon 4, one within intron 4 and one within intron 11. One of the promoter polymorphisms (G-1102A) lay within a consensus recognition site for the AP1 transcription factor. There was a significant association between the G-1102A genotype and BMD at the lumbar spine ( P = 0.01) and femoral neck ( P = 0.03). The association remained significant after correcting for age, weight, height, menopausal status/HRT use and smoking ( P = 0.008 for spine BMD and P = 0.03 for hip BMD), and homozygotes for the -1100 "G" allele had BMD values significantly higher than individuals who carried the -1100 "A" allele at both spine ( P = 0.007) and hip ( P = 0.047). Subgroup analysis showed that the association between G-1102A and BMD was restricted to premenopausal women who comprised 50.6% of the study group. None of the other polymorphisms or haplotypes were significantly associated with BMD in the study group as a whole or in any subgroup. Functional studies will need to be performed to determine the mechanisms that underlie this association, but we conclude that, in this relatively large population, allelic variation at the G-1102A site of TCIRG1 accounts for part of the heritable component of BMD in Scottish women, possibly by affecting peak bone mass.

Coinvolgimento Ureterale Bilaterale Nella Sindrome di Churg-Strauss: Descrizione di un Nuovo Caso

We report a case of Churg-Strauss syndrome, with bilateral ureteral involvement. We describe the endourological approach to the disease and we also discuss the literature about this argument.

Massive hematuria after transurethral resection of the prostate: management by intra-arterial embolization

A case of severe hemorrhage after TURP leading to hypovolemic shock and its successful management by superselective unilateral arterial embolization is described. The authors conclude that arterial embolization is a safe and effective procedure for severe prostatic hemorrhage that may be performed in selected cases when conservative means or fulguration of the prostatic fossa have failed to achieve the control of the bleeding. Adequate selection of the patients, correction of any underlying coagulation defects and a proper resection technique are surely the most important issues in preventing any postoperative bleeding.

[Etiopathogenesis and clinical aspects of nephrolithiasis--at present]

This paper deals of kidney stones, hard concretions that grow within the urinary tract, 71.5% of which have calcium contents. A high rate of recurrences underscores the importance of medical prevention with a variety of conservative (increased fluid intake and dietary modifications) and drug therapy (potassium citrate, potassium magnesium citrate, thiazides, allopurinol). In single stone formers and mild recurrent diseases, the conservative therapy may alone be effective and should be maintained in more severe recurrent disease, together with drug treatment. In particular, in idiopathic calcium oxalate nephrolithiasis, the importance of sodium restriction in the diet, that should reduce calcium excretion, has been recently shown, limiting the old assumption of the value of dietary calcium restriction; in fact normal or higher calcium intake, binding oxalate in the intestinal tract, seems to confer protection against stone formation. The urologic approach to urolithiasis has changed with the introduction of extracorporeal shock wave lithotripsy (ESWL), a technique that allows a relatively noninvasive removal of stones. Nevertheless ESWL does not change the propensity of recurrence of stone formers, and the importance of medical prevention remains paramount in the management of renal stone disease.

One shot: a novel method to dilate the nephrostomy access for percutaneous lithotripsy

BACKGROUND AND PURPOSE

The creation of the nephrostomy access is a fundamental step of percutaneous nephrolithotripsy (PCNL). Dilation of the track is usually achieved with multiple incremental flexible exchange dilators of the Amplatz type, metal telescoping dilators of the Alken type, or a balloon. Currently, balloon dilation is regarded as the most modern and safest system, though it has the disadvantage of relatively high cost. The aim of this study was to demonstrate that a procedure that we named "one shot," which consists of a single dilation of the track with a 25F or 30F Amplatz dilator, compares favorably in terms of efficacy, costs, and length with the other techniques of track dilation, without a significant increase in morbidity.

PATIENTS AND METHODS

Seventy-eight consecutive patients who underwent PCNL for stone disease from June 1998 to July 1999 were considered and divided into three groups according to the type of tract dilation used: A (Alken telescoping dilators), B (balloon), or C (one shot). Radiologic exposure, blood loss, and costs were evaluated.

RESULTS

The one-shot procedure compared favorably with both of the other dilation techniques without an increase in morbidity and with significant reductions in X-ray exposure and costs. Indeed, significant differences in estimated blood loss were observed between groups B and C and the minor bleeding for group C.

CONCLUSION

Our experience indicates that one-shot dilation is feasible in the majority of patients. It is as safe and effective as the technique regarded today as the gold standard but less time consuming and less expensive. These encouraging results should be confirmed by further studies.

The mutational spectrum of human malignant autosomal recessive osteopetrosis

Human malignant infantile osteopetrosis (arOP; MIM 259700) is a genetically heterogeneous autosomal recessive disorder of bone metabolism, which, if untreated, has a fatal outcome. Our group, as well as others, have recently identified mutations in the ATP6i (TCIRG1) gene, encoding the a3 subunit of the vacuolar proton pump, which mediates the acidification of the bone/osteoclast interface, are responsible for a subset of this condition. By sequencing the ATP6i gene in arOP patients from 44 unrelated families with a worldwide distribution we have now established that ATP6i mutations are responsible for approximately 50% of patients affected by this disease. The vast majority of these mutations (40 out of 42 alleles, including seven deletions, two insertions, 10 nonsense substitutions and 21 mutations in splice sites) are predicted to cause severe abnormalities in the protein product and are likely to represent null alleles. In addition, we have also analysed nine unrelated arOP patients from Costa Rica, where this disease is apparently much more frequent than elsewhere. All nine Costa Rican patients bore either or both of two missense mutations (G405R and R444L) in amino acid residues which are evolutionarily conserved from yeast to humans. The identification of ATP6i gene mutations in two families allowed us for the first time to perform prenatal diagnosis: both fetuses were predicted not to be affected and two healthy babies were born. This study contributes to the determination of genetic heterogeneity of arOP and allows further delineation of the other genetic defects causing this severe condition.