Imran Mushtaq

HNF1B Mutations Associate with Hypomagnesemia and Renal Magnesium Wasting

Mutations in hepatocyte nuclear factor 1B (HNF1B), which is a transcription factor expressed in tissues including renal epithelia, associate with abnormal renal development. While studying renal phenotypes of children with HNF1B mutations, we identified a teenager who presented with tetany and hypomagnesemia. We retrospectively reviewed radiographic and laboratory data for all patients from a single center who had been screened for an HNF1B mutation. We found heterozygous mutations in 21 (23%) of 91 cases of renal malformation. All mutation carriers had abnormal fetal renal ultrasonography. Plasma magnesium levels were available for 66 patients with chronic kidney disease (stages 1 to 3). Striking, 44% (eight of 18) of mutation carriers had hypomagnesemia (<1.58 mg/dl) compared with 2% (one of 48) of those without mutations (P < 0.0001). The median plasma magnesium was significantly lower among mutation carriers than those without mutations (1.68 versus 2.02 mg/dl; P < 0.0001). Because hypermagnesuria and hypocalciuria accompanied the hypomagnesemia, we analyzed genes associated with hypermagnesuria and detected highly conserved HNF1 recognition sites in FXYD2, a gene that can cause autosomal dominant hypomagnesemia and hypocalciuria when mutated. Using a luciferase reporter assay, we demonstrated HNF1B-mediated transactivation of FXYD2. These results extend the phenotype of HNF1B mutations to include hypomagnesemia. HNF1B regulates transcription of FXYD2, which participates in the tubular handling of Mg(2+), thus describing a role for HNF1B not only in nephrogenesis but also in the maintenance of tubular function.

Screening of newborn infants for cholestatic hepatobiliary disease with tandem mass spectrometry

Abstract Objective: To assess the feasibility of screening for cholestatic hepatobiliary disease and extrahepatic biliary atresia by using tandem mass spectrometry to measure conjugated bile acids in dried blood spots obtained from newborn infants at 7-10 days of age for the Guthrie test. Setting: Three tertiary referral clinics and regional neonatal screening laboratories. Design: Unused blood spots from the Guthrie test were retrieved for infants presenting with cholestatic hepatobiliary disease and from the two cards stored on either side of each card from an index child. Concentrations of conjugated bile acids measured by tandem mass spectrometry in the two groups were compared. Main outcome measures: Concentrations of glycodihydroxycholanoates, glycotrihydroxycholanoates, taurodihydroxycholanoates, and taurotrihydroxycholanoates. Receiver operator curves were plotted to determine which parameter (or combination of parameters) would best predict the cases of cholestatic hepatobiliary disease and extrahepatic biliary atresia. The sensitivity and specificity at a selection of cut off values for each bile acid species and for total bile acid concentrations for the detection of the two conditions were calculated. Results: 218 children with cholestatic hepatobiliary disease were eligible for inclusion in the study. Two children without a final diagnosis and five who presented at <14 days of age were excluded. Usable blood spots were obtained from 177 index children and 708 comparison children. Mean concentrations of all four bile acid species were significantly raised in children with cholestatic hepatobiliary disease and extrahepatic biliary atresia compared with the unaffected children (P<0.0001). Of 177 children with cholestatic hepatobiliary disease, 104 (59%) had a total bile acid concentration >33 μmol/l (97.5th centile value for comparison group). Of the 61 with extrahepatic biliary atresia, 47 (77%) had total bile acid concentrations >33 μmol/l Taurotrihydroxycholanoate and total bile acid concentrations were the best predictors of both conditions. For all cholestatic hepatobiliary disease, a cut off level of total bile acid concentration of 30 μmol/l gave a sensitivity of 62% and a specificity of 96%, while the corresponding values for extrahepatic biliary atresia were 79% and 96%. Conclusion: Most children who present with extrahepatic biliary atresia and other forms of cholestatic hepatobiliary disease have significantly raised concentrations of conjugated bile acids as measured by tandem mass spectrometry at the time when samples are taken for the Guthrie test. Unfortunately the separation between the concentrations in these infants and those in the general population is not sufficient to make mass screening for cholestatic hepatobiliary disease a feasible option with this method alone. Key messages The prognosis of cholestatic hepatobiliary disease in infancy, in particular biliary atresia, is improved by early detection Infants destined to present with cholestatic jaundice in the first few months of life have raised concentrations of bile acids in the blood spots obtained at 7-10 days for current neonatal screening programmes Tandem mass spectrometry can be used to detect this marker of neonatal cholestasis Unfortunately there is too much overlap between bile acid concentrations in infants with cholestasis and those in control infants for this to be used as a single screening test for cholestatic hepatobiliary disease in general and biliary atresia Tandem mass spectrometry is a powerful tool for neonatal screening but every potential application must be carefully assessed

Holistic management of DSD

Disorder of sex development (DSD) presents a unique challenge, both diagnostically and in terms of acute and longer-term management. These are relatively rare conditions usually requiring a multidisciplinary approach from the outset and the involvement of a tertiary centre for assessment and management recommendations. This article describes the structure of the multidisciplinary team (MDT) at our centre, with contributions from key members of the team regarding their individual roles. The focus is on the newborn referred for assessment of ambiguous genitalia, rather than on individuals who present in the adolescent period or at other times, although the same MDT involvement is likely to be required. The approach to the initial assessment and management is discussed and the subsequent diagnosis and follow-up presented, with emphasis on the importance of careful transition and long-term support.

Testicular and paratesticular tumours in the prepubertal population

Prepubertal testicular and paratesticular tumours are a rare group of tumours, distinct from postpubertal paediatric and adult tumours of this region. Tumours within this group are testicular germ-cell tumours (such as benign teratoma, epidermoid cyst and malignant yolk-sac tumours) and stromal tumours (such as juvenile granulosa-cell, Leydig-cell, and Sertoli-cell tumours). Paratesticular tumours can be benign (lipoma, leiomyoma, haemangioma) or malignant (rhabdomyosarcoma, melanotic neuroectodermal tumour of infancy). Because of their rarity, centralised pathology and treatment, and national collaborative clinical trials have been important in establishing the optimum management of malignant tumours in this group. We provide an up-to-date and comprehensive review of the clinical presentation, imaging, pathology, and clinical management of prepubertal paratesticular and testicular tumours.

Minimally invasive perinatal autopsies using magnetic resonance imaging and endoscopic postmortem examination ("keyhole autopsy"): feasibility and initial experience

Objective: Perinatal autopsy provides additional diagnostic information in a significant proportion of cases but parents and relatives frequently decline traditional postmortem (PM) examination, partly due to the unacceptability of the cosmetic effects of large incisions and concerns regarding organ retention. We present a novel minimally invasive autopsy method for fetal and neonatal PMexaminations, which includes PM magnetic resonance imaging (MRI) for assessment of anatomy and endoscopic internal examination to allow direct organ visualization and targeted tissue biopsy. Methods: Descriptive retrospective feasibility report of the first 10 perinatal cases undergoing endoscopic minimally invasive autopsy. Results: A minimally invasive autopsy (MIA) approach based on postmortem MRI (PM MRI) and endoscopic autopsy with tissue biopsy is feasible and effective with minimal cosmetic consequences compared to traditional PM examination. Endoscopic examination with tissue biopsy provided additional diagnostic information to PM MRI alone in the majority of cases. Conclusions: Endoscopic MIA is a feasible and potentially more acceptable approach to perinatal autopsy and provides an additional option for parents who do not agree to a traditional PM examination. This approach could result in increased utilization of investigations after death in this group of patients.

A Method for the Quantitation of Conjugated Bile Acids in Dried Blood Spots Using Electrospray Ionization-Mass Spectrometry

Bile acid concentrations are elevated in the blood of neonates with cholestatic hepatobiliary disorders providing a possible means of screening for treatable conditions including biliary atresia. A method is described for the determination of concentrations of conjugated bile acids in dried blood spots using electrospray ionization mass spectrometry. Bile acids were eluted from the blood spots using methanol containing, as internal standards, the taurine and glycine conjugates of D4-chenodeoxycholic acid and D4-cholic acid. The samples were then reconstituted in acetonitrile/water and injected by autosampler into the electrospray source operating in negative ion mode. Optimal conditions were determined for both single quadrupole and tandem mass spectrometry analysis. Blood spot bile acid profiles were studied in two groups of infants (<1 y), a cholestatic group(conjugated bilirubin >25 μmol/L; n = 49), and a control group(n = 96). The best discrimination between the two groups was provided by measurements of taurodihydroxycholanoates (normal <5 μmol/L; cholestatic group 18-94 μmol/L) and glycodihydroxycholanoates (normal <5μmol/L; cholestatic group 11-66 μmol/L). The method can also be adapted to detect unusual bile acids which are diagnostic of inborn errors of bile acid synthesis and peroxisomal disorders. The method is fast, reliable, reproducible, and relatively cheap; however, much more work is required to determine whether it can be used for mass screening for cholestasis. It will be necessary to show that measurement of bile acid concentrations in blood spots obtained at 7-10 d can be used to detect infants who currently present with jaundice, pale stools, and dark urine during the first 6 mo of life.

Y-type urethral duplication in the male

To present a single series of Y‐type duplication with an analysis of the presenting features, the management and outcome, as complete Y‐type urethral duplication in the male is a rare congenital anomaly that presents many challenges.

Further Experience With the Vascular Hitch (Laparoscopic Transposition of Lower Pole Crossing Vessels): An Alternate Treatment for Pediatric Ureterovascular Ureteropelvic Junction Obstruction

PURPOSE Standard treatment for ureterovascular ureteropelvic junction obstruction has been dismembered pyeloplasty. We previously reported the alternative technique of laparoscopic transposition of lower pole vessels (the vascular hitch) in pediatric patients. This report is an update of this select group of pediatric patients with intermediate followup. MATERIALS AND METHODS Patients underwent diagnostic renal sonography and (99m)technetium-mercaptoacetyltriglycine diuretic renography with additional magnetic resonance angiography in candidate patients. Radiographic criteria included moderate hydronephrosis with no caliceal dilatation and a well preserved cortex, poor renal drainage with preserved split function and lower pole crossing vessels. Intraoperative criteria included a normal ureter and ureteropelvic junction with peristalsis. Postoperatively patients were followed clinically, and with renal sonography and (99m)technetium-mercaptoacetyltriglycine renography at 1 and 2 months, respectively. Success was defined as symptom resolution with radiographic improvement in hydronephrosis and drainage with preserved renal function. RESULTS Nine boys and 11 girls 7 to 16 years old (mean age 12.5) underwent laparoscopic transposition of crossing vessels, including 3 with da Vinci robot assistance. Mean operative time was 90 minutes (range 47 to 140). Median hospital stay was 24 hours. No ureteral stents or urethral catheters were placed intraoperatively. At a mean followup of 22 months (range 12 to 42) 19 of 20 patients (95%) had been successfully treated. One patient who had recurrent pain underwent successful laparoscopic pyeloplasty. CONCLUSIONS At intermediate followup the laparoscopic vascular hitch procedure has been successful in treating patients with ureterovascular ureteropelvic junction obstruction. In these select patients this technique offers a feasible and durable alternative to standard dismembered pyeloplasty. Ongoing evaluation continues to ensure that the promising results endure.

Laparoscopic transposition of lower pole vessels – the ‘vascular hitch’: An alternative to dismembered pyeloplasty for pelvi-ureteric junction obstruction in children

OBJECTIVE Dismembered pyeloplasty is the traditional technique in the management of ureterovascular pelvi-ureteric junction obstruction (PUJO) in children. Controversy remains regarding the role of lower pole vessels as the sole aetiology for PUJO. Endopyelotomy and concomitant laparoscopic transposition of lower pole vessels for PUJO has been described in adults. We describe our technique of laparoscopic transposition of lower pole vessels in children with PUJO, leaving the PUJ intact. PATIENTS AND METHODS Thirteen patients (seven boys and six girls) with a mean age of 10.2 years (range 7-16 years) underwent laparoscopic transposition of lower pole vessels. Surgery was indicated on the basis of intermittent pain and ultrasound/MAG3 appearance of obstruction with or without reduced function. The technique involved laparoscopic transperitoneal mobilization of the lower pole vessels from the region of the PUJ thereby freeing the junction and transposing them superiorly onto the anterior wall of the pelvis. The main outcome measures were relief of pain and improvement in ultrasound appearance or drainage parameters on a postoperative MAG3 renogram performed within 4-6 weeks of surgery. RESULTS Median operating time was 92 min. All patients were discharged within 36 h of surgery. All patients remain pain free at a median of 6 months (range 3-18 months). Twelve patients showed good drainage on the postoperative MAG3 renogram and improvement in ultrasound appearance. One patient had recurrent symptoms requiring insertion of a JJ stent. She has undergone further laparoscopic exploration. The vessels were in their transposed position and there was a kink at the PUJ which was released. She had a vertical pyelotomy and transverse closure over the JJ stent with good results. CONCLUSION This technique is simple and requires less operating time. No anastomosis or temporary JJ stent is required. Our early results are very encouraging with no serious complications.

Mosaic Activating Mutations in GNA11 and GNAQ Are Associated with Phakomatosis Pigmentovascularis and Extensive Dermal Melanocytosis

Common birthmarks can be an indicator of underlying genetic disease but are often overlooked. Mongolian blue spots (dermal melanocytosis) are usually localized and transient, but they can be extensive, permanent, and associated with extracutaneous abnormalities. Co-occurrence with vascular birthmarks defines a subtype of phakomatosis pigmentovascularis, a group of syndromes associated with neurovascular, ophthalmological, overgrowth, and malignant complications. Here, we discover that extensive dermal melanocytosis and phakomatosis pigmentovascularis are associated with activating mutations in GNA11 and GNAQ, genes that encode Gα subunits of heterotrimeric G proteins. The mutations were detected at very low levels in affected tissues but were undetectable in the blood, indicating that these conditions are postzygotic mosaic disorders. In vitro expression of mutant GNA11R183C and GNA11Q209L in human cell lines demonstrated activation of the downstream p38 MAPK signaling pathway and the p38, JNK, and ERK pathways, respectively. Transgenic mosaic zebrafish models expressing mutant GNA11R183C under promoter mitfa developed extensive dermal melanocytosis recapitulating the human phenotype. Phakomatosis pigmentovascularis and extensive dermal melanocytosis are therefore diagnoses in the group of mosaic heterotrimeric G-protein disorders, joining McCune-Albright and Sturge-Weber syndromes. These findings will allow accurate clinical and molecular diagnosis of this subset of common birthmarks, thereby identifying infants at risk for serious complications, and provide novel therapeutic opportunities.