[The importance of early recognition of Prader-Willi syndrome]. / Het Prader-Willi-syndroom.

Due to its rare nature and subtle dysmorphisms, Prader-Willi syndrome can be challenging to recognize and diagnose in the neonatal period. Feeding difficulties and hypotonia ('floppy infant') are the most striking characteristics. Prader-Willi syndrome requires specific follow-up and treatment, emphasizing the importance of early recognition.We encountered an infant of three months old with severe hypotonia. The hypotonia ameliorated spontaneously over time, although feeding per nasogastric tube was necessary. There were no apparent dysmorphisms. Extensive genetic investigations showed a maternal uniparental disomy of chromosome 15, fitting with Prader-Willi syndrome explaining all symptoms. After excluding contraindications, treatment with growth hormone therapy was started. Parents were educated regarding medical emergencies specific for Prader-Willi syndrome ('medical alerts'). Although Prader-Willi syndrome is rare, it should always be considered in cases of neonatal hypotonia. Early recognition is paramount as specific recommendations and treatment are warranted.

Growth, body composition, and endocrine-metabolic profiles of individuals with Kleefstra syndrome provide directions for clinical management and translational studies.

Mendelian neurodevelopmental disorders caused by variants in genes encoding chromatin modification can be categorized as Mendelian disorders of the epigenetic machinery (MDEMs). These disorders have significant overlap in molecular pathways and phenotypes including intellectual disability, short stature, and obesity. Among the MDEMs is Kleefstra syndrome (KLFS), which is caused by haploinsufficiency of EHMT1. Preclinical studies have identified metabolic dysregulation and obesity in KLFS models, but proper clinical translation lacks. In this study, we aim to delineate growth, body composition, and endocrine-metabolic characteristics in a total of 62 individuals with KLFS. Our results revealed a high prevalence of childhood-onset overweight/obesity (60%; 28/47) with disproportionately high body fat percentage, which aligns perfectly with previous preclinical studies. Short stature was common (33%), likely due to advanced skeletal maturation. Endocrine-metabolic investigations showed thyroid dysregulation (22%; 9/41), elevated triglycerides, and decreased blood ammonia levels. Moreover, hand radiographs identified decreased bone mineralization (57%; 8/14) and negative ulnar variance (71%; 10/14). Our findings indicate a high (cardio)metabolic risk in KLFS. Therefore, we recommend monitoring of weight and endocrine-metabolic profile. Supporting a healthy lifestyle and screening of bone mineralization is advised. Our comprehensive results support translational research and contribute to a better understanding of MDEM-associated phenotypes.

Clinical and radiological assessment of scoliosis in Koolen-de Vries syndrome.

The Koolen-de Vries syndrome (KdVS) is a multisystem disorder characterized by developmental delay, intellectual disability, characteristic facial features, epilepsy, cardiovascular and urogenital malformations, and various musculoskeletal disorders. Scoliosis is a common feature. The aim of this study is to fill the gap in the current knowledge about scoliosis in individuals with KdVS and to provide recommendations for management and follow-up. In total, 54 individuals with KdVS were included in the study, with a mean age of 13.6 years (range 1.9-38.8 years). Spine radiographs, MR scans, and corresponding radiology reports were analyzed retrospectively for scoliosis and additional anomalies. The presence of scoliosis-related clinical conditions was assessed in participants' medical records and by use of a parent survey. Scoliosis was present in 56% of the participants (30/54) with a mean age of onset of 10.6 years and curve progression during the growth spurt. Prevalence at age 6, 10, and 18 years was, respectively, 9%, 41%, and 65%. Most participants were diagnosed with a single curve (13/24, 54%), of which five participants had a long C-curve type scoliosis. No significant risk factors for development of scoliosis could be identified. Severity was mostly classified as mild, although 29% (7/24) of the curves were larger than 30° at last follow-up. Bracing therapy was received in 13% (7/54), and surgical spinal fusion was warranted in 6% (3/54). Remarkably, participants with scoliosis received less often physical therapy compared to participants without scoliosis (P = 0.002). Scoliosis in individuals with KdVS should be closely monitored and radiologic screening for scoliosis and vertebrae abnormalities is recommended at diagnosis of KdVS, and the age of 10 and 18 years.

Feeding Problems in Patients with Noonan Syndrome: A Narrative Review.

Noonan syndrome (NS) belongs to the group of Noonan syndrome spectrum disorders (NSSD), which is a group of phenotypically related conditions. Feeding problems are often present not only in infancy but also in childhood, and even beyond that period. We describe the different aspects of feeding problems using a (theoretical) concept proposed in 2019. More than 50% of infants with NS develop feeding problems, and up to half of these infants will be tube-dependent for some time. Although, in general, there is a major improvement between the age of 1 and 2 years, with only a minority still having feeding problems after the age of 2 years, as long as the feeding problems continue, the impact on the quality of life of both NS infants and their caregivers may be significant. Feeding problems in general improve faster in children with a pathogenic PTPN11 or SOS1 variant. The mechanism of the feeding problems is complex, and may be due to medical causes (gastroesophageal reflux disease and delayed gastric emptying, cardiac disease and infections), feeding-skill dysfunction, nutritional dysfunction with increased energy demand, or primary or secondary psychosocial dysfunction. Many of the underlying mechanisms are still unknown. The treatment of the feeding problems may be a medical challenge, especially when the feeding problems are accompanied by feeding-skill dysfunction and psychosocial dysfunction. This warrants a multidisciplinary intervention including psychology, nutrition, medicine, speech language pathology and occupational therapy.

Young children with Noonan syndrome: evaluation of feeding problems.

Noonan syndrome (NS) is a common genetic syndrome with a high variety in phenotype. Even though genetic testing is possible, NS is still a clinical diagnosis. Feeding problems are often present in infancy. We investigated the feeding status of 108 patients with clinically and genetically confirmed NS. Only patients with a documented feeding status before the age of 6 were included. A distinction was made between patients with early onset feeding problems (< 1 year) and children with late onset feeding problems (> 1 year). Seventy-one of 108 patients had feeding problems, of which 40 patients required tube feeding. Children with a genetic mutation other than PTPN11 and SOS1 had significantly more feeding problems in the first year. Fifty-two of all 108 patients experienced early onset feeding problems, of which 33 required tube feeding. A strong decrease in prevalence of feeding problems was found after the first year of life. Fifteen children developed feeding problems later in life, of which 7 required tube feeding.Conclusion: Feeding problems occur frequently in children with NS, especially in children with NS based on genetic mutations other than PTPN11 and SOS1. Feeding problems develop most often in infancy and decrease with age. What is Known: • Young children with Noonan syndrome may have transient feeding problems. • Most of them will need tube feeding. What is New: • This is the first study of feeding problems in patients with clinically and genetically proven Noonan syndrome. • Feeding problems most often develop in infancy and resolve between the age of 1 and 2.

The effect of shiga toxin on weibel-palade bodies in primary human endothelial cells.

BACKGROUND/AIMS: Diarrhea-associated hemolytic uremic syndrome is associated with the presence of Shiga toxin (Stx1, Stx2 and several variants) in the circulation. The aim of this study is to examine the possible triggering effect of Stx1 on the exocytosis of Weibel-Palade bodies (WPbs). METHODS: Cultured human umbilical venous endothelial cells (HUVECs) and glomerular microvascular endothelial cells (GMVECs) were stimulated by thrombin and Stx1 in both static and flowing conditions. The amount of secreted von Willebrand factor (VWF) in the supernatant as well as the remaining intracellular fraction was determined. RESULTS: In HUVECs and in 2 out of 4 GMVECs, the stimulation of Stx1 in flow at 1 dyne/cm(2) resulted in a decrease of intracellular VWF. This is contrary to the results of Stx1 applied in static conditions. At a higher flow rate of 5 dyne/cm(2), no effect in GMVECs was observed. CONCLUSION: Stx1 can contribute, via an effect on WPbs, to the exocytosis of WPbs in flow conditions in HUVECs and probably in GMVECs. This results in the release of VWF, suggesting an initiating role of the coagulation system in the pathogenesis.

Vacuolisation of human microvascular endothelial cells by enterohaemorrhagic Escherichia coli.

Enterohaemorrhagic Escherichia coli (EHEC) cause haemolytic uraemic syndrome (HUS), a thrombotic microangiopathy resulting from endothelial injury in the renal glomeruli and other organs. EHEC virulence factors that damage the microvascular endothelium play therefore major roles in the pathogenesis of HUS. We identified an EHEC strain that vacuolates and kills primary human glomerular microvascular endothelial cells (GMVECs) and a human brain microvascular endothelial cell (HBMEC) line. Because the vacuolating effect closely resembles those elicited on other cells by the vacuolating cytotoxin of Helicobacter pylori (VacA), we designated the factor responsible for this effect EHEC vacuolating cytotoxin (EHEC-Vac). EHEC-Vac (a secreted non-serine protease protein) binds to HBMECs rapidly and irreversibly, vacuolates within 30 min after exposure and the effect is maximally apparent at 48 h. Despite the vacuolisation, HBMECs survive for several days before they undergo necrosis. Electron and immunofluorescence microscopy demonstrate that the vacuoles induced by EHEC-Vac originate from lysosomes. Accordingly, they stain with neutral red indicating an acidic microenvironment. Similar to VacA, the EHEC-Vac-mediated vacuolisation is both prevented and reverted by the vacuolar proton pump inhibitor bafilomycin A1, suggesting a similar mechanism of vacuole formation by these toxins. Despite the similarity of phenotypes elicited by EHEC-Vac and VacA, genomic DNA from the EHEC-Vac-producing strain failed to hybridise to a vacA probe, as well as to probes derived from presently known E. coli vacuolating toxins. Through its microvascular endothelium-injuring potential combined with the ability to induce interleukin 6 release from these cells EHEC-Vac might contribute to the pathogenesis of HUS.

Fractalkine and CX3CR1 mediate leukocyte capture by endothelium in response to Shiga toxin.

Shiga toxins (Stx) are the virulence factors of enterohemorrhagic Escherichia coli O157:H7, a worldwide emerging diarrheal pathogen, which precipitates postdiarrheal hemolytic uremic syndrome, the leading cause of acute renal failure in children. In this study, we show that Stx2 triggered expression of fractalkine (FKN), a CX3C transmembrane chemokine, acting as both adhesion counterreceptor on endothelial cells and soluble chemoattractant. Stx2 caused in HUVEC expression of FKN mRNA and protein, which promoted leukocyte capture, ablated by Abs to either endothelial FKN or leukocyte CX3CR1 receptor. Exposure of human glomerular endothelial cells to Stx2 recapitulated its FKN-inducing activity and FKN-mediated leukocyte adhesion. Both processes required phosphorylation of Src-family protein tyrosine kinase and p38 MAPK in endothelial cells. Furthermore, they depended on nuclear import of NF-kappaB and other stress-responsive transcription factors. Inhibition of their nuclear import with the cell-penetrating SN50 peptide reduced FKN mRNA levels and FKN-mediated leukocyte capture by endothelial cells. Adenoviral overexpression of IkappaBalpha inhibited FKN mRNA up-regulation. The FKN-mediated responses to Stx2 were also dependent on AP-1. In mice, both virulence factors of Stx-producing E. coli, Stx and LPS, are required to elicit hemolytic uremic syndrome. In this study, FKN was detected within glomeruli of C57BL/6 mice injected with Stx2, and further increased after Stx2 plus LPS coadministration. This was associated with recruitment of CX3CR1-positive cells. Thus, in response to Stx2, FKN is induced playing an essential role in the promotion of leukocyte-endothelial cell interaction thereby potentially contributing to the renal microvascular dysfunction and thrombotic microangiopathy that underlie hemolytic uremic syndrome due to enterohemorrhagic E. coli O157:H7 infection.

Shiga-toxin-induced firm adhesion of human leukocytes to endothelium is in part mediated by heparan sulfate.

BACKGROUND: Shiga toxin (Stx) is the main pathogenic factor in the haemolytic-uraemic syndrome (HUS). Stx damages the renal endothelium, which leads to inflammation and coagulation. Endothelial heparan sulfate proteoglycans (HSPG), and heparan sulfate in particular, play an important role in the inflammatory process by acting as a ligand for l-selectin. Furthermore, leukocytes are able to interact with chemokines bound to HSPG (examples are IL-8, RANTES and MCP-1). This leads to an activation of integrins on leukocytes and results in more stable leukocyte-endothelial wall adhesion. In this study, we have evaluated the effect of a subtoxic dose of Stx1 and Stx2 on the HSPG and its role in adhesion of leukocytes. METHODS: Primary human umbilical venous endothelial cells (HUVEC) and primary human glomerular microvascular endothelial cells (GMVEC) were incubated for 24 h with a subtoxic dose of Stx1 or Stx2. Then, cells were treated with heparan sulfate-degrading enzyme heparitinase I or left untreated, followed by determination of binding leukocytes to endothelial cells in a parallel plate flow chamber. RESULTS: In both cell types, Stx increased the amount of firmly adherent leukocytes. After removal of endothelial heparan sulfate, the number of adhering leukocytes decreased. CONCLUSIONS: HSPG have a distinctive role in adhesion of leukocytes to endothelial cells stimulated by a subtoxic dose of Stx.

Interactions of Shiga-like toxin with human peripheral blood monocytes.

The cytotoxic effect of Shiga-like toxin (Stx; produced by certain Escherichia coli strains) plays a central role in typical hemolytic uremic syndrome (HUS). It damages the renal endothelium by inhibiting the cellular protein synthesis. Also, the monocyte has a specific receptor for Stx but is not sensitive for the cytotoxic effect. In this work, monocytes were studied as a potential transporter for Stx to the renal endothelium. Coincubation of isolated human monocytes loaded with Stx and target cells (vero cells and human umbilical vascular endothelial cells) were performed. Transfer was determined by measuring the protein synthesis of target cells and by flow cytometry. Furthermore, the effect of a temperature shift on loaded monocytes was investigated. Stx-loaded monocytes reduced the protein synthesis of target cells. After adding an antibody against Stx, incomplete recovery occurred. Also, adding only the supernatant of coincubation was followed by protein synthesis inhibition. Stx detached from its receptor on the monocyte after a change in temperature, and no release was detected without this temperature shift. Although the monocyte plays an important role in the pathogenesis of HUS, it has no role in the transfer of Stx.

Adult and paediatric patients with minimal change nephrotic syndrome show no major alterations in glomerular expression of sulphated heparan sulphate domains.

BACKGROUND: Minimal change nephrotic syndrome (MCNS) is the most frequent form of nephrotic syndrome in childhood. In the glomerular basement membrane (GBM) of adult patients with MCNS, a reduced expression of a specific heparan sulphate (HS) domain has been reported. In children with MCNS, urinary activity of the HS-degrading enzyme heparanase was increased. It is, therefore, possible that a decreased GBM HS expression is associated with the pathogenesis of proteinuria in patients with MCNS. METHODS: In this study, HS in glomeruli of five adult and six paediatric patients with MCNS were analysed by immunofluorescence staining using four different antibodies, each defining a specific sulphated HS domain. The pediatric patients were subdivided into three groups depending on the presence or absence of podocyte foot process effacement, the level of proteinuria and prednisone administration at the time of the biopsy. In addition, kidneys of rats with adriamycin nephropathy (ADRN), a model for MCNS, were included in the study. RESULTS: Expression of sulphated HS domains was not aberrant in adult or paediatric patients compared with control subjects. Children with and without proteinuria had the same HS content. In contrast, rats with ADRN showed a decreased glomerular expression of sulphated HS domains. CONCLUSIONS: These results suggest that in patients with MCNS proteinuria is not associated with major changes in glomerular expression of sulphated HS domains.

A missense mutation in factor I (IF) predisposes to atypical haemolytic uraemic syndrome.

A genetic predisposition involving complement regulatory genes has become evident in some patients with atypical HUS. In this paper, a patient with a heterozygous missense mutation in factor I (IF) is described. Although the serum level of IF was normal, a mild functional defect in the alternative pathway of complement could be demonstrated in the affected members of the family. After an episode of atypical HUS, chronic renal insufficiency started at the age of 15 months. Recurrence of HUS, with loss of the renal transplant, occurred twice in this patient. The recurrence of HUS in the graft was not reflected by haematological abnormalities (haemolysis, thrombocytopenia). One additional transplant was lost due to arterial thrombosis of the renal artery. This report confirms the gloomy outcome of renal transplants in patients with an IF deficiency. New therapies should be evaluated in these patients.

Lack of specific binding of Shiga-like toxin (verocytotoxin) and non-specific interaction of Shiga-like toxin 2 antibody with human polymorphonuclear leucocytes.

BACKGROUND: After gastrointestinal infection with Shiga-like toxin (Stx) producing Escherichia coli, the toxin is transported from the intestine to the renal microvascular endothelium. This is the main target for Stx in humans. Previous studies indicated that polymorphonuclear leucocytes (PMN) could serve as carriers for Stx in the systemic circulation. As at a later stage we could not confirm these data, we performed new studies. METHODS: The binding of Stx1 to PMN was determined in vitro (isolated human PMN and whole blood) and in vivo (injection in mice). The specificity of binding of an antibody against Stx2 to PMN from patients with haemolytic uraemic syndrome (HUS) was determined. This was compared with binding to PMN from healthy controls, and patients after haemodialysis (HD) or on peritoneal dialysis (PD). Furthermore, PMN were incubated with Stx to study possible activation. RESULTS: No specific binding of Stx1 to PMN could be detected. After intravenous injection of the toxin in mice, it was not associated with PMN. The binding of an antibody against Stx2 to PMN was detected in both patients with HUS and patients after HD, but not in patients on PD. Stx was not able to activate PMN. CONCLUSIONS: PMN are not acting as transporter for Stx in the pathogenesis of HUS. The interaction of a Stx antibody with PMN from HUS patients is not specific as it can also be observed in patients after HD (possibly due to activation of the PMN). Therefore, binding of Stx antibody to PMN is not reliable as a diagnostic tool for HUS.

Follow-up and treatment of adults with cystinosis in the Netherlands.

BACKGROUND: Cystinosis is a rare autosomal recessive disease, caused by intracellular cystine accumulation due to a defect in the lysosomal cystine carrier. Treatment with cysteamine favours the transport of cystine out of the lysosomes, diminishes organ damage, and postpones the progression of renal failure. The extra-renal deposition of cystine continues after renal transplantation, leading to later complications. The objective of this study was to evaluate the follow-up, the occurrence of late complications, the social status, and the adequacy of cysteamine treatment in adult patients with cystinosis. METHODS: The medical histories of 10 adult cystinosis patients aged 19-36 years were studied. The impairment of thyroid function, central nervous system, endocrine pancreas, and ocular manifestations, as well as treatment with cysteamine were evaluated. RESULTS: Eight patients received in total 12 renal grafts, one patient was dialysed and one received conservative treatment for chronic renal failure. Extra-renal complications were noted in six patients, loss of visual acuity in four, hypothyroidism in three, diabetes mellitus in one, cerebral atrophy and epilepsy in one, and swallowing difficulties in two patients. Ophthalmic control was not performed in two patients, thyroid function was not controlled in two and glycaemia not controlled in two patients. Seven patients received 2100-4000 mg cysteamine per day in 2 (n=2), 3 (n=1), 4 (n=3), or 6 (n=1) doses. Cystine concentration in leukocytes was measured once or twice a year in eight patients and was within the recommended range only in three patients. CONCLUSION: A high rate of extra-renal complications in adults with nephropathic cystinosis was found. Optimizing the cysteamine therapy may attenuate these complications. Better communication between paediatric and 'adult's' nephrologists is needed to improve follow-up and treatment of grown-up cystinosis patients.