Dealing with the incidental finding of secondary variants by the example of SRNS patients undergoing targeted next-generation sequencing.

BACKGROUND: Steroid-resistant nephrotic syndrome (SRNS) is a severe cause of progressive renal disease. Genetic forms of SRNS can present with autosomal recessive or autosomal dominant inheritance. Recent studies have identified mutations in multiple podocyte genes responsible for SRNS. Improved sequencing methods (next-generation sequencing, NGS) now promise rapid mutational testing of SRNS genes. METHODS: In the present study, a simultaneous screening of ten SRNS genes in 37 SRNS patients was performed by NGS. RESULTS: In 38 % of the patients, causative mutations in one SRNS gene were found. In 22 % of the patients, in addition to these mutations, a secondary variant in a different gene was identified. CONCLUSIONS: This high incidence of accumulating sequence variants was unexpected but, although they might have modifier effects, the pathogenic potential of these additional sequence variants seems unclear so far. The example of molecular diagnostics by NGS in SRNS patients shows that these new sequencing technologies might provide further insight into molecular pathogenicity in genetic disorders but will also generate results, which will be difficult to interpret and complicate genetic counseling. Although NGS promises more frequent identification of disease-causing mutations, the identification of causative mutations, the interpretation of incidental findings and possible pitfalls might pose problems, which hopefully will decrease by further experience and elucidation of molecular interactions.

Markers of childhood lupus nephritis indicating disease activity.

Current treatment regimens for childhood lupus nephritis (LN) are associated with significant side-effects and toxicity in vulnerable phases of growth and development. The paucity of biomarkers particularly in childhood impedes the appropriate clinical management and the development of new therapeutics. We analyzed markers of immune system (BAFF, RANTES), complement (Bb, C1q, C3d-CIC, C5a) and endothelial cell activation (sVCAM-1) in children with LN (n=22, mean age 14.8±4.7 years), nephrotic syndrome (n=13) and age-matched healthy controls (n=20) to define parameters that correlate with LN activity. Complement fragments of the alternative (Bb, p=0.0004) classical (C3d-CIC, p<0.0001) and common pathway (C5a, p<0.0001) and the levels of BAFF (p<0.0001), RANTES (p=0.0002) and sVCAM-1 (p=0.0004) were significantly higher in active compared to inactive LN. Activation of complement was associated with the occurrence of anti-C1q antibodies and reduced complement C1q. Complement-activation fragments highly correlated with the markers for immune system and endothelial cell activation. The ensemble of these parameters may be of great value in identifying early flares or remissions of childhood LN, and moreover may prove useful in the assessment of new treatments and in determining the optimization of their use.

15 years of continent urinary diversion and enterocystoplasty in children and adolescents: the Würzburg experience.

OBJECTIVE: To assess the long-term results of continent urinary diversion (CUD) and enterocystoplasty (ECP) in children with irreversible lower urinary tract dysfunction (LUTD). PATIENTS AND METHODS: The study included 44 children with irreversible LUTD who had a CUD or ECP between 1992 and 2007. Patients were followed for the functional outcome of surgery with a focus on complications related to the reservoir, bowel, uretero-intestinal anastomosis and upper urinary tract. Data were collected prospectively and outcomes were evaluated using a standardized protocol. RESULTS: The median (range) follow-up was 7.3 (3.5-17) years. Complete continence was achieved in 94% overall, i.e. in 95% of patients with continent cutaneous diversion, 83% with ECP and all children with continent anal diversion. Upper urinary tract and renal function remained stable in 89% and 95%, respectively. Surgical intervention was required for adhesive small bowel ileus in 6%, stoma-related complications in 39%, ureteric stenosis in 8%, and stone formation in 19%. Of these complications, 54% required only minor interventions; 41% of patients needed prophylactic alkaline substitution. Bowel habits remained unchanged or improved in 68%. CONCLUSION: Our results show that CUD and ECP in children are effective procedures with acceptable long-term complication rates. However, conclusions from our data might be limited, as this was a small study including highly selected patients treated at one tertiary academic centre. Being an audit of practice in our institution and given the variety of concepts, these results might differ from those centres using other approaches in the surgical treatment of LUTD. Importantly, this type of surgery should be restricted to carefully selected patients in whom all attempts of restoring the LUT failed.

Successful treatment of severe arterial hypotension and anuria in a preterm infant with renal tubular dysgenesis- a case report.

BACKGROUND: Oligohydramnios sequence can be caused by renal tubular dysgenesis (RTD), a rare condition resulting in pulmonary and renal morbidity. Besides typical features of Potter-sequence, the infants present with severe arterial hypotension and anuria as main symptoms. Establishing an adequate arterial blood pressure and sufficient renal perfusion is crucial for the survival of these infants. CASE PRESENTATION: We describe a male preterm infant of 34 + 0 weeks of gestation. Prenatally oligohydramnios of unknown cause was detected. After uneventful delivery and good adaptation the infant developed respiratory distress due to a spontaneous right-sided pneumothorax and required thoracocentesis and placement of a chest tube; he showed no major respiratory concerns thereafter and needed only minimal ventilatory support. Echocardiography revealed no abnormalities, especially no pulmonary hypertension. However, he suffered from severe arterial hypotension and anuria refractory to catecholamine therapy (dobutamine, epinephrine and noradrenaline). After 36 h of life, vasopressin therapy was initiated resulting in an almost immediate stabilization of arterial blood pressure and subsequent onset of diuresis. Therapy with vasopressin was necessary for three weeks to maintain adequate arterial blood pressure levels and diuresis. Sepsis and adrenal insufficiency were ruled out as inflammation markers, microbiological tests and cortisol level were normal. At two weeks of age, our patient developed electrolyte disturbances which were successfully treated with fludrocortisone. He did not need renal replacement therapy. Genetic analyses revealed a novel compound hyterozygous mutation of RTD. Now 17 months of age, the patient is in clinically stable condition with treatment of fludrocortisone and sodium bicarbonate. He suffers from stage 2 chronic kidney disease; blood pressure, motor and cognitive development are normal. CONCLUSIONS: RTD is a rare cause of oligohydramnios sequence. Next to pulmonary hypoplasia, severe arterial hypotension is responsible for poor survival. We present the only second surviving infant with RTD, who did not require renal replacement therapy during the neonatal period. It can be speculated whether the use of vasopressin prevents renal replacement therapy as vasopressin increases urinary output by improving renal blood flow.

COQ6 mutations in human patients produce nephrotic syndrome with sensorineural deafness.

Steroid-resistant nephrotic syndrome (SRNS) is a frequent cause of end-stage renal failure. Identification of single-gene causes of SRNS has generated some insights into its pathogenesis; however, additional genes and disease mechanisms remain obscure, and SRNS continues to be treatment refractory. Here we have identified 6 different mutations in coenzyme Q10 biosynthesis monooxygenase 6 (COQ6) in 13 individuals from 7 families by homozygosity mapping. Each mutation was linked to early-onset SRNS with sensorineural deafness. The deleterious effects of these human COQ6 mutations were validated by their lack of complementation in coq6-deficient yeast. Furthermore, knockdown of Coq6 in podocyte cell lines and coq6 in zebrafish embryos caused apoptosis that was partially reversed by coenzyme Q10 treatment. In rats, COQ6 was located within cell processes and the Golgi apparatus of renal glomerular podocytes and in stria vascularis cells of the inner ear, consistent with an oto-renal disease phenotype. These data suggest that coenzyme Q10-related forms of SRNS and hearing loss can be molecularly identified and potentially treated.