The genetics of infantile hypertrophic pyloric stenosis. A reanalysis

Our experience of laparoscopic pyloromyotomy with ultrasound-guided parameters

Traditional management of infantile Hypertrophic Pyloric Stenosis is open pyloromyotomy after initial adequate resuscitation of the patient. From 1991, laparoscopic approach is considered feasible and safe. Today, diagnosis of hypertrophic pyloric stenosis is made most often made by ultrasound. With use of ultrasound-guided parameters (length of pyloric tumour and thickness of pyloric tumour), we could avoid ‘incomplete pyloromyotomy’ and ‘mucosal perforation’ (most common complications in laparoscopic approach) to achieve 100% adequacy and safety in laparoscopic pyloromyotomy.

A novel missense mutation in the transcription factor FOXF1 cosegregating with infantile hypertrophic pyloric stenosis in the extended pedigree linked to IHPS5 on chromosome 16q24

BACKGROUND

The aim was to identify susceptibility alleles for infantile hypertrophic pyloric stenosis (IHPS) in a pedigree previously linked to IHPS5 on chromosome 16q24.

METHODS

We screened the positional and functional candidate gene FOXF1 by Sanger sequencing in a single affected individual. All family members for whom DNA was available were genotyped to determine cosegregation status of the putative causal variant. Immunofluorescence studies were performed to compare the cellular localization of wildtype and mutant form of the protein. Transcriptional activity was compared using a luciferase assay.

RESULTS

A single novel substitution in FOXF1 (c.416G>A) predicted to result in a missense mutation (R139Q) was shown to cosegregate with disease trait. It was not seen in 560 control chromosomes nor has it been reported in ExAC or ESP. The R139Q substitution affects a conserved arginine residue within the DNA-binding domain of FOXF1. The transcriptional activity of the mutant FOXF1 protein is significantly reduced in comparison to wild-type.

CONCLUSION

These results provide strong evidence that the R139Q substitution in FOXF1 causes IHPS in this family and imply a novel pathological pathway for the condition. They further support a role for FOXF1 in the regulation of embryonic and neonatal development of the gastro-intestinal tract.

White paper on guidelines concerning enteric nervous system stem cell therapy for enteric neuropathies

Over the last 20 years, there has been increasing focus on the development of novel stem cell based therapies for the treatment of disorders and diseases affecting the enteric nervous system (ENS) of the gastrointestinal tract (so-called enteric neuropathies). Here, the idea is that ENS progenitor/stem cells could be transplanted into the gut wall to replace the damaged or absent neurons and glia of the ENS. This White Paper sets out experts' views on the commonly used methods and approaches to identify, isolate, purify, expand and optimize ENS stem cells, transplant them into the bowel, and assess transplant success, including restoration of gut function. We also highlight obstacles that must be overcome in order to progress from successful preclinical studies in animal models to ENS stem cell therapies in the clinic.

Maternal and pregnancy characteristics and risk of infantile hypertrophic pyloric stenosis

BACKGROUND/PURPOSE

The incidence of infantile hypertrophic pyloric stenosis (IHPS) in Sweden decreased dramatically during the 1990s. The aim of the study was to examine IHPS risk factors and the possible change in them as the incidence declined.

METHODS

This is a case-control study including 3608 surgically treated IHPS cases and 17588 matched controls during 1973-2008. Cases were identified in the Swedish National Patient Register and data on possible risk factors were collected from the Swedish Medical Birth Register. The association between study variables and IHPS was analyzed using conditional logistic regression for the whole study period and separately for periods with high and low IHPS incidences.

RESULTS

Prematurity (OR, 2.54; 95% CI, 2.06-3.14), caesarean delivery (OR, 1.67; 95% CI, 1.51-1.86), maternal smoking (OR, 1.82; 95% CI, 1.53-2.16), and young maternal age (< 20yrs) (OR, 1.42; 95% CI, 1.17-1.73) were associated with an increased IHPS risk. Birth order 2 (OR, 0.78; 95% CI, 0.71-0.85) or more was associated with a lower IHPS risk. ORs for smoking increased at low incidence rate.

CONCLUSION

We report caesarean section, prematurity, primiparity, young maternal age, and smoking as significant IHPS risk factors. The impact of smoking was higher during periods with a low incidence.

Advances in infantile hypertrophic pyloric stenosis

Infantile hypertrophic pyloric stenosis (IHPS) is a common condition in infancy, characterized by an acquired narrowing of the pylorus, which requires surgery. These infants usually present with projectile, nonbilious vomiting, with a palpable 'olive' in the abdomen and sometimes a 'peristaltic wave' after being fed with formula or breast milk. Although IHPS is a common disorder, its etiology is largely unknown. Surgical intervention is the standard treatment, preoperative preparation, however is essential to optimal outcome. In this review, the latest advances in IHPS regarding epidemiology, etiology, diagnostics and treatment will be discussed.

The ins and outs of pyloromyotomy: what we have learned in 35 years

PURPOSE/BACKGROUND

The aim of the study is to evaluate a large series of infantile hypertrophic pyloric stenosis (IHPS) patients treated by one pediatric surgeon focusing on their diagnostic difficulties and complications.

METHODS

From July 1969 to December 2003 (inclusive), the charts of 791 infants with IHPS were retrospectively reviewed.

RESULTS

There were 647 (82%) males and 144 (18%) females; mean age was 38 days, median 51 (range 7 days-10 months). When ultrasonography (US) was routinely used (1990), the age at diagnosis decreased to <40 days. The mean weight before and after routine US was 3.2 kg, median 3 (range 1.5-6). Twenty-five (3.1%) were premature at diagnosis, mean age 49 days, median 56, (range 1-3 months) and mean weight 2.5 kg, median 2.3 (range 1.5-3.2). Eighty-one (10%) had a positive family history. Forty-four (5%) were non-Caucasians. Seventy-five (9 %) had other medical conditions, anomalies and/or associated findings. Sixty (7%) patients had abnormal preoperative electrolytes. Ten (1.2%) pylorics occurred after newborn operations. Of the entire total (791) who were treated, there were 13 (1.7%) not operated on. All operations were done open initially through one of two right upper quadrant incisions, and then through an upper midline incision under general endotracheal anesthesia; 14 (1.7 %) had concomitant procedures. Prophylactic antibiotics (from 1982) decreased the wound infection rate to 3.9%. There were a total of 87 (10%) complications which included 9 (1.1%) intraoperative, (including mistaken diagnoses) 78 (9%) postoperative: 59 (2%) early (<1 month) and 19 (2.4%) late (>1 month). The 13 (1.6%) postoperative transfers (12 from non-pediatric surgeons) had 16 (18%) complications (including 1 death); five (33%) requiring reoperation (4 incomplete, 1 perforation). There were two deaths.

CONCLUSIONS

IHPS should be considered in any vomiting infant. US allows earlier diagnosis. Serious complications are uncommon and avoidable, but recognizable and easily corrected. Higher surgeon volume of pyloromyotomies (>14 per year) is associated with fewer complications.

Hypertrophic pyloric stenosis in twins; genetic or environmental factors

The etiology of infantile hypertrophic pyloric stenosis (IHPS) remains obscure. Over 120 years after the condition has become a clinical entity the debate whether the cause of IHPS is genetic, environmental or both, has not yet reached a final conclusion. Herein, we present a pair of monozygotic male twins with IHPS together with a review of the literature. We aimed to support genetic pre-disposition in the epidemiology of IHPS, adding a twin data to the literature and to review the associated articles about the pathogenesis and inheritance patterns.

The clinical features of infantile hypertrophic pyloric stenosis in Chinese Han population: analysis from 1998 to 2010

Objective

To investigate clinical features of infantile hypertrophic pyloric stenosis (IHPS) in Chinese Han population.

Methods

Three hundred and sixteen hospitalized patients with IHPS from January 1998 to February 2010 were retrospectively reviewed, and data including patient's sex, onset age, other coexisting congenital defects, pyloric circular muscle thickness evaluated by ultrasonograph, serum electrolytes concentration, and results of arterial blood gas analysis on admission were collected. The patients were divided into two groups: the duration between first onset and admission less than or equal to 10 days (early onset group), and more than 10 days (late onset group). The results of arterial blood gas and serum electrolyte concentration were compared between the two groups.

Results

There were 271 males and 45 females in 316 patients; the onset age ranged between 1 and 351 (26.5±26.6) days. The birth weight ranged between 1.6 and 4.5 (3.23±0.44) kilograms; coexisting congenital defects were found in 65 cases (20.6%). Pyloric circular muscle thickness was 4–8 (5.4±1.0) millimetres (mm). For the early onset group, the rates of hypokalemia, hypochloraemia and hypercapnia were significantly lower than those in the late onset group (18.67% VS 50%, P<0.0001; 46.03% VS 71.01%, P = 0.003; 56.58% VS 83.44%, P = 2.17×10⁻⁵; respectively).

Conclusions

The symptom duration in Chinese Han population was longer than that in other populations. And as the prolongation of symptom duration, the incidence of acid-base imbalance increased significantly. Infants with persistent vomiting at the age of 3∼5 weeks after birth should be considered IHPS, and go to hospital as soon as possible in order to reduce the incidence of hypokalemia, hypochloraemia and hypercapnia, and avoid deterioration.

An update on common gastrointestinal emergencies

The evaluation of the child with acute abdominal pain often poses as a diagnostic challenge due to the wide range of diagnoses. Surgical emergencies need to be rapidly identified and managed appropriately to minimize morbidity and mortality. Presenting symptoms, clinical examination, and laboratory findings can guide selection of diagnostic imaging. This article reviews common surgical causes of abdominal pain in children.

Plasma lipids, genetic variants near APOA1, and the risk of infantile hypertrophic pyloric stenosis

IMPORTANCE

Infantile hypertrophic pyloric stenosis (IHPS) is a serious condition in which hypertrophy of the pyloric sphincter muscle layer leads to gastric outlet obstruction. Infantile hypertrophic pyloric stenosis shows strong familial aggregation and heritability, but knowledge about specific genetic risk variants is limited.

OBJECTIVES

To search the genome comprehensively for genetic associations with IHPS and validate findings in 3 independent sample sets.

DESIGN, SETTING, AND PARTICIPANTS

During stage 1, we used reference data from the 1000 Genomes Project for imputation into a genome-wide data set of 1001 Danish surgery-confirmed samples (cases diagnosed 1987-2008) and 2371 disease-free controls. In stage 2, the 5 most significantly associated loci were tested in independent case-control sample sets from Denmark (cases diagnosed 1983-2010), Sweden (cases diagnosed 1958-2011), and the United States (cases diagnosed 1998-2005), with a total of 1663 cases and 2315 controls.

MAIN OUTCOMES AND MEASURES

Association of genetic variation with the presence of infantile hypertrophic pyloric stenosis.

RESULTS

We found a new genome-wide significant locus for IHPS at chromosome 11q23.3. The single-nucleotide polymorphism (SNP) with the lowest P value at the locus, rs12721025 (odds ratio [OR], 1.59; 95% CI, 1.38-1.83; P = 1.9 × 10(-10)), is located 301 bases downstream of the apolipoprotein A-I (APOA1) gene and is correlated (r2 between 0.46 and 0.80) with SNPs previously found to be associated with levels of circulating cholesterol. For these SNPs, the cholesterol-lowering allele consistently was associated with increased risk of IHPS.

CONCLUSIONS AND RELEVANCE

This study identified a new genome-wide significant locus for IHPS. Characteristics of this locus suggest the possibility of an inverse relationship between levels of circulating cholesterol in neonates and IHPS risk, which warrants further investigation.

Infantile hypertrophic pyloric stenosis in twins

Infantile hypertrophic pyloric stenosis (IHPS) is a common surgical cause of vomiting, which requires surgery in infant. There is the complete or partial obstruction of pylorus due to hypertrophy of circular muscle of the pylorus leading gastric outlet obstruction. The occurrence of IHPS in dizygotic twins is rarer and the theory of genetic origin alone does not explain it. Recent literature points to the association of bottle feeding in singletons to be a major aetiological factor for this condition. Here, we present a rare case of dizygotic twins who were bottle-fed and were affected with IHPS. We review the literature and focus on the question of whether this condition in twins supports a genetic or environmental origin of IHPS.

Infantile hypertrophic pyloric stenosis--genetics and syndromes

Infantile hypertrophic pyloric stenosis (IHPS) is a common condition in neonates that is characterized by an acquired narrowing of the pylorus. The aetiology of isolated IHPS is still largely unknown. Classic genetic studies have demonstrated an increased risk in families of affected infants. Several genetic studies in groups of individuals with isolated IHPS have identified chromosomal regions linked to the condition; however, these associations could usually not be confirmed in subsequent cohorts, suggesting considerable genetic heterogeneity. IHPS is associated with many clinical syndromes that have known causative mutations. Patients with syndromes associated with IHPS can be considered as having an extreme phenotype of IHPS and studying these patients will be instrumental in finding causes of isolated IHPS. Possible pathways in syndromic IHPS include: (neuro)muscular disorders; connective tissue disorders; metabolic disorders; intracellular signalling pathway disturbances; intercellular communication disturbances; ciliopathies; DNA-repair disturbances; transcription regulation disorders; MAPK-pathway disturbances; lymphatic abnormalities; and environmental factors. Future research should focus on linkage analysis and next-generation molecular techniques in well-defined families with multiple affected members. Studies will have an increased chance of success if detailed phenotyping is applied and if knowledge about the various possible causative pathways is used in evaluating results.

Bottle-feeding and the Risk of Pyloric Stenosis

OBJECTIVES

Bottle-feeding has been suggested to increase the risk of pyloric stenosis (PS). However, large population-based studies are needed. We examined the effect of bottle-feeding during the first 4 months after birth, by using detailed data about the timing of first exposure to bottle-feeding and extensive confounder information.

METHODS

We performed a large population-based cohort study based on the Danish National Birth Cohort, which provided information on infants and feeding practice. Information about surgery for PS was obtained from the Danish National Patient Register. The association between bottle-feeding and the risk of PS was evaluated by hazard ratios (HRs) estimated in a Cox regression model, adjusting for possible confounders.

RESULTS

Among 70148 singleton infants, 65 infants had surgery for PS, of which 29 were bottle-fed before PS diagnosis. The overall HR of PS for bottle-fed infants compared with not bottle-fed infants was 4.62 (95% confidence interval [CI]: 2.78-7.65). Among bottle-fed infants, risk increases were similar for infants both breast and bottle-fed (HR: 3.36 [95% CI: 1.60-7.03]), formerly breastfed (HR: 5.38 [95% CI: 2.88-10.06]), and never breastfed (HR: 6.32 [95% CI: 2.45-16.26]) (P = .76). The increased risk of PS among bottle-fed infants was observed even after 30 days since first exposure to bottle-feeding and did not vary with age at first exposure to bottle-feeding.

CONCLUSIONS

Bottle-fed infants experienced a 4.6-fold higher risk of PS compared with infants who were not bottle-fed. The result adds to the evidence supporting the advantage of exclusive breastfeeding in the first months after birth.

Pre- and perinatal risk factors for pyloric stenosis and their influence on the male predominance

Pyloric stenosis occurs with a nearly 5-fold male predominance. To what extent this is due to environmental factors is unknown. In a cohort of all children born in Denmark, 1977-2008, the authors examined the association between pre- and perinatal exposures and pyloric stenosis and investigated whether these factors modified the male predominance. Information on pre- and perinatal factors and pyloric stenosis was obtained from national registers. Poisson regression models were used to estimate rate ratios. Among 1,925,313 children, 3,174 had surgery for pyloric stenosis. The authors found pyloric stenosis to be significantly associated with male sex, age between 2 and 7 weeks, early study period, being first born, maternal smoking during pregnancy, preterm delivery, small weight for gestational age, cesarean section, and congenital malformations. Among cases, 2,595 were males and 579 were females. Lower male predominance was associated with age at diagnosis outside the peak ages, early study period, no maternal smoking during pregnancy, preterm delivery, and congenital malformations. The authors have previously found a strong familial aggregation of pyloric stenosis indicating a genetic influence. This study shows that environmental factors during and shortly after pregnancy also play a role and that several of these modify the strong male predominance.

Common variants near MBNL1 and NKX2-5 are associated with infantile hypertrophic pyloric stenosis

Infantile hypertrophic pyloric stenosis (IHPS) is a severe condition characterized by hypertrophy of the pyloric sphincter muscle. We conducted a genome-wide association study (GWAS) on 1,001 surgery-confirmed cases and 2,401 controls from Denmark. The six most strongly associated loci were tested in a replication set of 796 cases and 876 controls. Three SNPs reached genome-wide significance. One of these SNPs, rs11712066 (odds ratio (OR) = 1.61; P = 1.5 × 10(-17)) at 3p25.1, is located 150 kb upstream of MBNL1, which encodes a factor that regulates splicing transitions occurring shortly after birth. The second SNP, rs573872 (OR = 1.41; P = 4.3 × 10(-12)), maps to an intergenic region at 3p25.2 approximately 1.3 Mb downstream of MBNL1. The third SNP, rs29784 (OR = 1.42; P = 1.5 × 10(-15)) at 5q35.2, is 64 kb downstream of NKX2-5, which is involved in development of cardiac muscle tissue and embryonic gut development.

Genome-wide linkage analysis in families with infantile hypertrophic pyloric stenosis indicates novel susceptibility loci

Infantile hypertrophic pyloric stenosis (IHPS) is a common cause of upper gastrointestinal obstruction during infancy. A multifactorial background of the disease is well established. Multiple susceptibility loci including the neuronal nitric oxide synthase (NOS1) gene have previously been linked to IHPS, but contradictory results of linkage studies in different materials indicate genetic heterogeneity. To identify IHPS susceptibility loci, we conducted a genome-wide linkage analysis in 37 Swedish families. In regions where the Swedish material showed most evidence in favor of linkage, 31 additional British IHPS families were analyzed. Evidence in favor of significant linkage was observed in the Swedish material to two loci on chromosome 2q24 (non-parametric linkage (NPL) =3.77) and 7p21 (NPL=4.55). In addition, evidence of suggestive linkage was found to two loci on chromosome 6p21 (NPL=2.97) and 12q24 (NPL=2.63). Extending the material with British samples did not enhance the level of significance. Regions with linkage harbor interesting candidate genes, such as glucagon-like peptide-2 (GLP-2 encoded by the glucagon gene GCG), NOS1, motilin (MLN) and neuropeptide Y (NPY). The coding exons for GLP-2, and NPY were screened for mutations with negative results. In conclusion, we could confirm suggestive linkage to the region harboring the NOS1 gene and detected additional novel susceptibility loci for IHPS.

Genomic variants in the coding region of neuronal nitric oxide synthase (NOS1) in infantile hypertrophic pyloric stenosis

BACKGROUND

Infantile hypertrophic pyloric stenosis (IHPS) is a common childhood pathology affecting 1 to 5:1000 newborns, with a genetic background suggested by familial occurrence. Neuronal nitric oxide synthase (NOS1) is a candidate gene owing to its role in the relaxation of smooth musculature and the association of the -84g>a variant of NOS1 with IHPS.

METHODS

We investigated NOS1 through sequencing of the complete NOS1 coding region in DNA from 43 patients with IHPS compared the genotype frequencies to 47 controls using the Cochran-Armitage trend or Fisher exact tests.

RESULTS

We found 19 polymorphisms in the coding region of NOS1. The variants c.3827-42_3827-43 del_insTA and c.+276 c>t were more frequent in IHPS with statistically significant exact P values (P = .010 and P = .039, respectively) yet failed to show significance after Bonferroni adjustment for multiple testing. We have also found a marginally significant occurrence of the variants c.-460A (P = .065) and c.2823+15G (P = .076). There was a significant correlation between the variants c.2706C>T ⬄ c.2823+15A>G, (r(2) = 1.00) and c.3258 C>T ⬄ c.3235+31A>G (r(2) = 1.00).

CONCLUSIONS

We conclude that NOS1 variants are present in patients with IHPS yet show no significant statistical association with the IHPS phenotype, suggesting at best an adjuvant role for NOS1 in IHPS.

Infantile hypertrophic pyloric stenosis: An association in twins?

BACKGROUND

The etiology of infantile hypertrophic pyloric stenosis (IHPS) remains a mystery. Some suspected risk factors include birth rank, maternal age, sex, family history and monozygosity in twins. Various theories attempt to explain the etiology of IHPS. Scientific research suggests that enteric neuronal damage and nitric oxide synthase dysfunction may be implicated, but the consensus is that environmental modification must exist to account for the variability in its occurrence.

METHOD

Four cases of concordant occurrences of IHPS in twins were examined to determine the history and outcome of IHPS development in twins. Three sets were dizygotic and one was monozygotic. Of the eight infants, three were female, including the one monozygotic pair. In all four cases, a time lag existed between the development of symptomatic onset of IHPS in twin A and twin B. In one set, sonographic confirmation, performed because of IHPS diagnosis in the twin sibling, occurred concurrently with onset of vomiting, leading to early surgery before fluid and electrolyte imbalances developed.

CONCLUSIONS

Despite the lack of agreement as to whether the cause of IHPS is genetic, environmental or both, the high concordance rate seen in twins is indisputable. Thus, the empirical evidence provides credence to consider examining the asymptomatic co-twin when one of the twins presents with IHPS.

Infantile hypertrophic pyloric stenosis: evaluation of three positional candidate genes, TRPC1, TRPC5 and TRPC6, by association analysis and re-sequencing

Infantile hypertrophic pyloric stenosis (IHPS) is the most common inherited form of gastrointestinal obstruction in infancy with a striking male preponderance. Infants present with vomiting due to gastric outlet obstruction caused by hypertrophy of the smooth muscle of the pylorus. Two loci specific to extended pedigrees displaying autosomal dominant inheritance have been identified. A genome scan identified loci on chromosomes 11q14-q22 and Xq23-q24 which are predicted to be responsible for a subset of smaller families with IHPS demonstrating non-Mendelian inheritance. The two linked chromosomal regions both harbour functional candidate genes which are members of the canonical transient receptor potential (TRPC) family of ion channels. Both TRPC5 (Xq23-q24) and TRPC6 (11q14-q22) have a potential role in smooth muscle control and hypertrophy. Here, we report suggestive evidence for a third locus on chromosome 3q12-q25 (Zmax = 2.7, p < 0.004), a region which harbours a third TRPC gene, TRPC1. Fine mapping of all three genes using a tagSNP approach and re-sequencing identified a SNP in the promoter region of TRPC6 and a missense variant in exon 4 of TRPC6 which may be putative causal variants.

Epidemiological features of infantile hypertrophic pyloric stenosis in Taiwan: a national study 1996-2004

BACKGROUND AND AIM

The incidence of infantile hypertrophic pyloric stenosis (IHPS) varies among different countries and is supposed to be lower in Asian countries than in Western countries. However, the incidence of IHPS in Taiwan has not been well investigated.

METHODS

The National Health Insurance (NHI) program was implemented in Taiwan in 1995 and covers most of the population (>99%). We used the NHI database to investigate the epidemiological features of IHPS in Taiwan and to compare the data with that of other countries.

RESULTS

We identified 962 new IHPS cases during the period from 1996 to 2004. The overall incidence of IHPS was 0.39 (0.34-0.50) cases per 1000 live births. The estimation was 0.39-0.59 per 1000 live births after adjustment for the misdiagnosis rate. The peak incidence (0.58 per 1000 live births) occurred in winter in 1999. Rates were consistently higher in male subjects. The 1-year survival rate was not significantly different in the patients receiving pyloromyotomy in medical centers, regional hospitals, and district hospitals (P=0.389).

CONCLUSIONS

Taiwan had the second lowest incidence of IHPS reported in the medical literature. IHPS patients can be successfully treated in district and general hospitals with good prognosis.

Testosterone levels in umbilical-cord blood and risk of pyloric stenosis

OBJECTIVE

The risk of infantile hypertrophk pylonc stenosis is ∼5 times more common in male than female infants. It has been hypothesized that the higher risk among male infants is associated with high levels of testosterone causing hypertrophy of the pylorus muscle. To test this hypothesis, we examined the association between the testosterone levels in the umbilical-cord blood and the risk of infantile hypertrophic pyloric stenosis.

PATIENTS AND METHODS

We conducted a matched case-control study nested in the Danish National Birth Cohort using risk-set sampling. From a cohort of 101 042 pregnancies, we identified umbilical-cord blood samples from 46 case subjects (43 male and 3 female infants) who developed infantile hypertrophic pyloric stenosis in the first year of life and 150 gender- and gestational age-matched control subjects. The testosterone levels were measured by liquid chromatography-tandem mass spectrometry. Rate ratios were estimated by using conditional logistic regression.

RESULTS

In male infants, the mean testosterone level at birth was 0.78 nmol/L in case subjects and 0.91 nmol/L in control subjects. The rate of infantile hypertrophic pyloric stenosis was inversely, albeit insignificantly, associated with the testosterone levels in male infants; there was a 29% (95% confidence interval: -46% to 65%; P = 35) lower rate per nmol/L. The association was not modified according to age, gestational age, or birth order.

CONCLUSIONS

We found no support for the hypothesis that high testosterone levels in the umbilical-cord blood are strongly associated with a subsequently higher risk for infantile hypertrophic pyloric stenosis in male infants.

Interstitial cells of Cajal, the Maestro in health and disease

Interstitial cells of Cajal (ICC) are important players in the symphony of gut motility. They have a very significant physiological role orchestrating the normal peristaltic activity of the digestive system. They are the pacemaker cells in gastrointestinal (GI) muscles. Absence, reduction in number or altered integrity of the ICC network may have a dramatic effect on GI system motility. More understanding of ICC physiology will foster advances in physiology of gut motility which will help in a future breakthrough in the pharmacological interventions to restore normal motor function of GI tract. This mini review describes what is known about the physiologic function and role of ICCs in GI system motility and in a variety of GI system motility disorders.

Lack of association between nNOS -84G>A polymorphism and risk of infantile hypertrophic pyloric stenosis in a Chinese population

BACKGROUND

Infantile hypertrophic pyloric stenosis (IHPS) is one of the most common gastrointestinal obstructions in the infancy requiring surgery. Reduced expression of neuronal nitric oxide synthase (nNOS), which plays an important role in the regulation of the human pyloric muscle, is thought to underlie IHPS. The role of nNOS in IHPS has been supported by the genetic association of a functional regulatory nNOS polymorphism (-84G>A) with IHPS in whites. We reasoned that the corroboration of this association in a population of different ethnic origin would prompt follow-up studies and further investigation of the IHPS pathology at molecular level. Thus, we attempted to reproduce the original findings in a Chinese population of comparable size in what would be the first genetic study on IHPS conducted in Chinese.

METHODS

nNOS -84G>A genotypes were analyzed in 56 patients and 86 controls by polymerase chain reaction and DNA sequencing. Logistic regression was used to compute odds ratios.

RESULTS

Our study could not corroborate the association previously reported. Although the frequency of the IHPS-associated allele (-84A) in controls (0.205) was similar to that reported for white controls, there was a dramatic difference in -84A frequencies between white and Chinese patients (0.198). Similarly, there was no difference in the nNOS -84G>A genotype distribution between patients and controls, even when the GA and AA genotypes were combined to compare GG genotype (odds ratio, 1.01; 95% confidence interval, 0.47-2.19).

CONCLUSIONS

Failure to replicate the initial finding does not detract from its validity, because genetic effects may differ across populations. Differences across populations in linkage disequilibrium and/or allele frequencies may contribute to this lack of replication. The role nNOS in IHPS awaits further investigation.

New insights into the pathogenesis of infantile pyloric stenosis

Infantile hypertrophic pyloric stenosis (IHPS) is the most common surgical cause of vomiting in infants. Despite numerous hypotheses, the aetiopathogenesis of IHPS is not fully understood. Genetic, extrinsic and hormonal factors have been implicated in the pathogenesis of the disease. Furthermore, abnormalities of various components of the pyloric muscle such as smooth muscle cells, growth factors, extracellular matrix elements, nerve and ganglion cells, synapses, nerve supporting cells, neurotransmitters and interstitial cells of Cajal have been reported. Recently, genetic studies have identified susceptibility loci for IHPS and molecular studies have concluded that smooth muscle cells are not properly innervated in IHPS.

Linkage of monogenic infantile hypertrophic pyloric stenosis to chromosome 16q24

Infantile hypertrophic pyloric stenosis (IHPS) is the most common inherited form of gastrointestinal obstruction in infancy. The disease is considered a paradigm for the sex-modified model of multifactorial inheritance and affects males four times more frequently than females. However, extended pedigrees consistent with autosomal dominant inheritance have been documented. We have analysed data from an extended IHPS family including eight affected individuals (five males and three females) and mapped the disease locus to chromosome 16q24 (LOD score=3.7) through an SNP-based genome wide scan. Fourteen additional multiplex pedigrees did not show evidence of linkage to this region, indicating locus heterogeneity.

Genome-wide high-density SNP-based linkage analysis of infantile hypertrophic pyloric stenosis identifies loci on chromosomes 11q14-q22 and Xq23

Infantile hypertrophic pyloric stenosis (IHPS) has an incidence of 1-8 per 1000 live births and is inherited as a complex sex-modified multifactorial trait with a striking male preponderance. Syndromic and monogenic forms exist, and two loci have been identified. Infants present with vomiting due to gastric-outlet obstruction caused by hypertrophy of the smooth muscle of the pylorus. A genome-wide SNP-based high-density linkage scan was carried out on 81 IHPS pedigrees. Nonparametric and parametric linkage analysis identified loci on chromosomes 11q14-q22 (Z(max) = 3.9, p < 0.0001; HLOD(max) = 3.4, alpha = 0.34) and Xq23 (Z(max) = 4.3, p < 0.00001; HLOD(max) = 4.8, alpha = 0.56). The two linked chromosomal regions each harbor functional candidate genes that are members of the canonical transient receptor potential (TRPC) family of ion channels and have a potential role in smooth-muscle control and hypertrophy.

Absence of motilin gene mutations in infantile hypertrophic pyloric stenosis

BACKGROUND

Erythromycin treatment before 2 weeks of age has been shown to increase the risk of infantile hypertrophic pyloric stenosis (IHPS) up to 10 times. Erythromycin is a motilin agonist, a hormone that induces gastrointestinal contractions. The purpose of this study was to investigate if mutations in the motilin gene (MLN) cause IHPS or if the V15A polymorphism in MLN is associated with the disease.

METHODS

The MLN was screened for mutations, and the V15A polymorphism was determined in a total of 57 patients with IHPS using polymerase chain reaction and DNA sequencing. The polymorphism genotype and allele frequencies among the patients were compared with 184 controls.

RESULTS

We detected 3 different, not previously reported, MLN sequence variants in 4 patients. One of these variants results in an amino acid exchange in the motilin signal peptide (A25G). All 3 detected sequence variants were also found in controls or were not inherited with the disease. We found no significant association between the V15A polymorphism and the disease.

CONCLUSIONS

We have excluded the MLN coding region as a major cause of IHPS. Future studies will evaluate the importance of this metabolic pathway in the pathogenesis of IHPS.

Recurrent pyloric stenosis: to dilate or operate? A preliminary report

PURPOSE

Idiopathic hypertrophic pyloric stenosis is a common surgical problem in infants, and pyloromyotomy is almost always successful in alleviating the obstruction. There are few reports in the literature that discuss recurrent pyloric stenosis as opposed to incomplete pyloromyotomy. We report 2 such babies with different cures.

METHODS

The health records department files were electronically searched for the number of infants at our children's hospital with hypertrophic pyloric stenosis seen over the past 30 years (1973-2003), and the recurrences were reviewed.

RESULTS

Recurrent pyloric stenosis was encountered in 2 cases (<0.07%). Balloon dilatation was first tried in both cases and was successful in 1 case; redo pyloromyotomy was required for the second case.

CONCLUSION

Recurrent pyloric stenosis is rare. Fluoroscopic balloon dilatation of the pylorus warrants further study as the first choice for curing this problem, and if unsuccessful, redo pyloromyotomy.

Postoperative pyloric stenosis in the newborn: a forgotten problem

PURPOSE

Postoperative vomiting in newborns is a common finding usually attributed to the original surgery. We report 10 newborns whose postoperative course was complicated by pyloric stenosis.

METHODS

We reviewed the charts of all newborns who had pyloric stenosis diagnosed after a major abdominothoracic operation over the past 30 years (1973-2003) at a single children's hospital.

RESULTS

Ten cases of pyloric stenosis were diagnosed in postoperative newborns (esophageal atresia [3], small bowel atresia [2], diaphragmatic hernia, fetus-in-fetu, imperforate anus, lung biopsy, malrotation [1]). Their mean gestational age was 36 weeks, birth weight was 3.2 kg, and age at newborn operation was 2 days. Their postoperative feeds started on the sixth day (mean), and the pyloric stenosis vomiting started on the 14th day. It took a mean of 12 days to make the diagnosis of pyloric stenosis, and this was done entirely by diagnostic imaging. Mean age at pyloromyotomy was 3 1/2 weeks. A new incision was used in 7 patients. Postoperative feedings started on the first day; all did well. There were 3 complications (bowel obstruction), all requiring operation.

CONCLUSION

Unfortunately, this review offers no specific insight or novel advice to help the readership think about the diagnosis in such a postoperative setting.

Infantile hypertrophic pyloric stenosis: an infectious cause?

The aetiology of infantile hypertrophic pyloric stenosis (IHPS) remains unclear. The aim of this study was to test the hypothesis that a common bacterium, Helicobacter pylori (HP) may be implicated in the pathogenesis of IHPS. Thirty-nine consecutive infants with confirmed IHPS had their stool analysed with an enzyme immunoassay for the presence of HP. An age/sex-matched group of infants with unrelated surgical conditions were also tested. No positive results for the presence of HP stool antigen were obtained in the study nor the control group. The results of this study demonstrate no causative link between HP and IHPS. A genetic basis has been implicated for IHPS. However, evidence does exist that IHPS is a condition acquired after birth and that an infective agent may be involved in the pathogenesis. Further studies are required to elucidate perinatal factors that may induce the expression of this condition in a genetically sensitive individual.

Conservative treatment of infantile hypertrophic pyloric stenosis with intravenous atropine sulfate does not replace pyloromyotomy

Pyloromyotomy as described by Weber and Ramstedt has been the standard therapy for infantile hypertrophic pyloric stenosis since the 1960's and conservative therapy has been abandoned. The objective of this study was to test the effectiveness of systemic atropine applied intravenously for 7 days as a conservative therapeutic strategy and as an alternative to primary operation. Forty-two consecutive term infants with infantile hypertrophic pyloric stenosis were enrolled in the study over a period of 5 years. After confirmation of the diagnosis they all received intravenous atropine at a dose of 0.04 mg/(kg day) and increased by 0.01 mg/(kg day) up to 0.12 mg/(kg day), given as 6-8 single doses per/day. Nine pairs of parents requested that their child should be operated before completing the 7 days of medical therapy. Surgery was necessary in 8 of the remaining 33 infants (24,.2%) who did not improve after 7 days of conservative treatment. Successful treatment with i.v. atropine sulfate was achieved only in 25/33 term infants at an average maximal dose of 0.11 mg/(kg day), without any major side effects. Intravenous atropine sulfate has been considered as a potential alternative therapeutic strategy in the treatment of infantile hypertrophic pyloric stenosis. Clinical improvement however was often not seen before the 6th or 7th day of intravenous treatment. A success rate for the conservative approach of only 75% at day 7 in our study does not favour atropine therapy, in view of success rates above 95% with surgical repair.

Salt-wasting 21-hydroxylase deficiency congenital adrenal hyperplasia and pyloric stenosis in two Hispanic brothers

The differential diagnosis of vomiting and dehydration in the first month of life includes congenital adrenal hyperplasia (CAH) and pyloric stenosis (PS). Each diagnosis may mask the presence of the other, requiring careful evaluation and follow-up. We document the occurrence of CAH and PS in two Hispanic siblings.

The continuing enigma of pyloric stenosis of infancy: a review

Striking features of the descriptive epidemiology of pyloric stenosis of infancy have been identified but until recently have not suggested any useful etiologic lead. The disease first received serious attention approximately 100 years ago and has since occurred throughout the Western world at a rate between 2 and 5 per thousand live births; it appears to be uncommon elsewhere. Its age distribution is essentially limited to the period between the third and eighth weeks after birth. It is 4 to 5 times more common in boys than girls. It is less common in blacks than whites in the United States and less common among Asians than whites in the United States and elsewhere. Its incidence is highest in first-born infants. Evidence on a role for maternal age is not consistent. The disease re-occurs in families with sufficient frequency to incite the interest of geneticists, although no genetic model yet proposed offers a better basis for counseling than do the empiric observations on which it is based. Monozygous twins are concordant for the disease not much more frequently than are dizygous twins, and indeed not a great deal more often than nontwin siblings, which should prompt a search for environmental explanations of the disease's familial nature. Sharp declines in the incidence of the disease in Denmark and Sweden during the 1990s led to the hypothesis that infants sleeping in the prone position-a practice discouraged with some success by Scandinavian campaigns to reduce the frequency of sudden infant death syndrome (SIDS)-may also be at increased risk of pyloric stenosis. If supported, this hypothesis may offer the first-ever possibility of reducing the frequency of this disease, as well as SIDS. If the hypothesis is not supported, the recent declines in the disease in Denmark and Sweden add another facet to its enigmatic nature.

Hypertrophic pyloric stenosis in twins: same genes or same environments?

The aetiology of infantile hypertrophic pyloric stenosis (IHPS) remains obscure. Cases in twins, usually monozygotic, have been sporadically reported as evidence for the genetic origin of the disease. We present a case of IHPS in a pair of dizygotic male twins together with a review of the literature, focusing on the question of whether the twin cases actually support a genetic or an acquired nature of IHPS.

Pyloric stenosis: unusual presentations and rare assoclations

Pyloric stenosis is a common paediatric surgical condition with a well-recognised pattern of clinical features. Diagnosis is usually straightforward and a Ramstedt pyloromyotomy is curative. We present three patients who developed pyloric stenosis incidentally during the management of other primary surgical conditions. Issues of diagnostic difficulty following presentation of pyloric stenosis in the post-operative period (all three patients), its rare syndromic associations (one patient) and its management in this unusual situation are discussed. An awareness of the unusual presentations of pyloric stenosis during treatment for other primary surgical conditions can help in earlier diagnosis and treatment.

The Vomiting Neonate: A Review of the ACR Appropriateness Criteria and Ultrasound’s Role in the Workup of Such Patients

Ultrasound (US) plays a central role in the diagnostic imaging workup for infantile vomiting. This paper reviews the major causes of vomiting in the first months of life and the use of US and other modalities for their imaging assessment. The differential diagnostic possibilities are reviewed by examining 3 clinical scenarios of bilious vomiting during the first days of life, nonbilious vomiting since birth, and projectile vomiting first occurring after several weeks of life. These are the 3 scenarios that were used for the American College of Radiology (ACR) Appropriateness Criteria for Vomiting in Infants up to 3 Months of Age.

Single-nucleotide promoter polymorphism alters transcription of neuronal nitric oxide synthase exon 1c in infantile hypertrophic pyloric stenosis

Infantile hypertrophic pyloric stenosis (IHPS), characterized by enlarged pyloric musculature and gastric-outlet obstruction, is associated with altered expression of neuronal nitric oxide synthase (nNOS). Here we have studied molecular mechanisms by which nNOS gene expression is altered in pyloric tissues of 16 infants with IHPS and 9 controls. A significant decreased expression of total nNOS mRNA was found by quantitative RT-PCR in IHPS after normalization against GAPDH, which predominantly affected exon 1c with a reduction of 88% compared with controls (P < 0.001). After normalization against the neuronal-specific gene PGP9.5, expression of exon 1c was still decreased (P < 0.001), whereas expression of exon 1f was increased significantly (P = 0.001), indicating a compensatory up-regulation of this nNOS mRNA variant. DNA samples of 16 IHPS patients and 81 controls were analyzed for nNOS exon 1c promoter mutations and single-nucleotide polymorphism (SNP). Sequencing of the 5'-flanking region of exon 1c revealed mutations in 3 of 16 IHPS tissues, whereas 81 controls showed the wild-type sequence exclusively. Carriers of the A allele of a previously uncharacterized nNOS exon 1c promoter SNP (-84G --> A) had increased risk for development of IHPS (odds ratio, 8.0; 95% confidence interval, 2.5-25.6). Reporter gene assays revealed an unchanged promoter activity for mutations but a approximately 30% decrease for the -84A SNP (P < 0.001). In summary, our findings indicate that genetic alterations in the nNOS exon 1c regulatory region influence expression of the nNOS gene and may contribute to the pathogenesis of IHPS.

Analysis of the threshold liability model provides new understanding of causation in autoimmune diseases

Autoimmune diseases include a heterogeneous group of complex traits, the causes of which are essentially unknown. The threshold liability model is a hypothesis that has a significant influence on thinking about causation in these diseases. Here, I analyze this model and assess its utility in understanding causation in autoimmunity. According to the model, members of a population have a normal distribution of genetic liability for a particular autoimmune disease. Further, a threshold value exists for each autoimmune disease such that an individual develops disease when his/her liability exceeds the threshold value; environmental and stochastic factors and epistatic gene interactions may increase or decrease an individual's disease liability. There are, however, two main problems with the threshold liability model. First, for a particular autoimmune disease, the threshold value divides a population into two distinct groups that consist either of affected or of healthy individuals. I show that this dichotomous division is inaccurate and misleading. Second, the threshold value corresponds to the occurrence of a component-cause of disease, i.e. when an appropriate collection of causative factors for a particular autoimmune disease is present, the disease must inevitably occur. I argue, however, that the disease contribution of essentially unknown random or stochastic factors to causation is at least similar in importance to the contributions of genetic and environmental factors. These stochastic factors add a significant element of unpredictability to the effects of genetic and environmental factors. Consequently causes in autoimmunity do not act deterministically, which is implied by the component-cause concept. Instead, the role of causative factors is to alter disease risk. I therefore reject the threshold liability model and conclude that a probabilistic approach provides the only reasonable way to understand causation in autoimmune diseases. This conclusion has important implications for other deterministic hypotheses in autoimmunity including other component-cause hypotheses.