Genotype-dependency of butyrate efficacy in children with congenital chloride diarrhea

Approach to Congenital Diarrhea and Enteropathies (CODEs)

Congenital diarrhea and enteropathies (CODEs) constitute a group of rare genetic disorders characterized by severe diarrhea and malabsorption in the neonatal period or early infancy. Timely diagnosis and treatment is essential to prevent life-threatening complications, including dehydration, electrolyte imbalance, and malnutrition. This review offers a simplified approach to the diagnosis of CODEs, with a specific focus on microvillus inclusion disease (MVID), congenital tufting enteropathy (CTE), congenital chloride diarrhea (CLD), and congenital sodium diarrhea (CSD). Patients with CODEs typically present with severe watery or occasionally bloody diarrhea, steatorrhea, dehydration, poor growth, and developmental delay. Therefore, it is crucial to thoroughly evaluate infants with diarrhea to rule out infectious, allergic, or anatomical causes before considering CODEs as the underlying etiology. Diagnostic investigations for CODEs encompass various modalities, including stool tests, blood tests, immunological studies, endoscopy and biopsies for histology and electron microscopy, and next-generation sequencing (NGS). NGS plays a pivotal role in identifying the genetic mutations responsible for CODEs. Treatment options for CODEs are limited, often relying on total parenteral nutrition for hydration and nutritional support. In severe cases, intestinal transplantation may be considered. The long-term prognosis varies among specific CODEs, with some patients experiencing ongoing intestinal failure and associated complications. In conclusion, the early recognition and accurate diagnosis of CODEs are of paramount importance for implementing appropriate management strategies. Further research and advancements in genetic testing hold promise for enhancing diagnostic accuracy and exploring potential targeted therapies for these rare genetic disorders.

Short-chain fatty acids: linking diet, the microbiome and immunity

The short-chain fatty acids (SCFAs) butyrate, propionate and acetate are microbial metabolites and their availability in the gut and other organs is determined by environmental factors, such as diet and use of antibiotics, that shape the diversity and metabolism of the microbiota. SCFAs regulate epithelial barrier function as well as mucosal and systemic immunity via evolutionary conserved processes that involve G protein-coupled receptor signalling or histone deacetylase activity. Indicatively, the anti-inflammatory role of butyrate is mediated through direct effects on the differentiation of intestinal epithelial cells, phagocytes, B cells and plasma cells, and regulatory and effector T cells. Intestinally derived SCFAs also directly and indirectly affect immunity at extra-intestinal sites, such as the liver, the lungs, the reproductive tract and the brain, and have been implicated in a range of disorders, including infections, intestinal inflammation, autoimmunity, food allergies, asthma and responses to cancer therapies. An ecological understanding of microbial communities and their interrelated metabolic states, as well as the engineering of butyrogenic bacteria may support SCFA-focused interventions for the prevention and treatment of immune-mediated diseases.

Deficient butyrate metabolism in the intestinal microbiome is a potential risk factor for recurrent kidney stone disease

Intestinal microbiome dysbiosis is a known risk factor for recurrent kidney stone disease (KSD) with prior data suggesting a role for dysfunctional metabolic pathways other than those directly utilizing oxalate. To identify alternative mechanisms, the current study analyzed differences in the metabolic potential of intestinal microbiomes of patients (n = 17) and live-in controls (n = 17) and determined their relevance to increased risk for KSD using shotgun metagenomic sequencing. We found no differences in the abundance of genes associated with known oxalate degradation pathways, supporting the notion that dysfunction in other metabolic pathways plays a role in KSD. Further analysis showed decreased abundance of key enzymes involved in butyrate biosynthesis in patient intestinal microbiomes. Furthermore, de novo construction of microbial genomes showed that the majority of genes significantly enriched in non-stone formers are affiliated with Faecalibacterium prausnitzii, a major butyrate producer. Specifically pertaining to butyrate metabolism, the majority of abundant genes mapped back to F. prausnitzii, Alistipes spp., and Akkermansia muciniphila. No differences were observed in ascorbate or glyoxylate metabolic pathways. Collectively, these data suggest that impaired bacterial-associated butyrate metabolism may be an oxalate-independent mechanism that contributes to an increased risk for recurrent KSD. This indicates that the role of the intestinal microbiome in recurrent KSD is multi-factorial, which is representative of the highly intertwined metabolic nature of this complex environment. Future bacteria-based treatments must not be restricted to targeting only oxalate metabolism.

Early Energy Intake and Amino Acid Profile in Preterm Newborns: A Quasi-Experimental Study

(1) Background: An increased protein intake via parenteral nutrition (PN) in early life is associated with an improvement of the nitrogen balance in preterm newborns. However, the role of energy intake on amino acid (AA) utilization provided by PN remains to be defined. We investigated the effects of energy intake on blood AA levels and profiles. (2) Methods: Quasi-experimental study including preterm very low birth weight newborns who received an energy enhanced PN (Cohort A) or an energy standard PN (Cohort B), with a similar protein amount in the first week of life. Blood AA levels were measured between three and seven days of life (T0) and at fifteen days of life (T1) and compared between the two study cohorts. (3) Results: AA levels of 40 newborns from each group were analyzed. No difference was found for total essential and non-essential blood AA concentration at T0 between the two study cohorts. At T1, we found a significantly higher blood concentration of leucine, isoleucine and proline, and a significantly lower concentration of tyrosine in Cohort B. However, multivariate analysis did not confirm this result. (4) Conclusions: An enhanced PN protocol in terms of energy but not of protein did not influence AA levels and profiles. Considering the high risk of side effects, we suggest exercising caution when administering high energy intake via PN in the first week of life.

Fecal microbiota in congenital chloride diarrhea and inflammatory bowel disease

Background and aims

Subjects with congenital chloride diarrhea (CLD; a defect in solute carrier family 26 member 3 (SLC26A3)) are prone to inflammatory bowel disease (IBD). We investigated fecal microbiota in CLD and CLD-associated IBD. We also tested whether microbiota is modulated by supplementation with the short-chain fatty acid butyrate.

Subjects and methods

We recruited 30 patients with CLD for an observational 3-week follow-up study. Thereafter, 16 consented to oral butyrate substitution for a 3-week observational period. Fecal samples, collected once a week, were assayed for calprotectin and potential markers of inflammation, and studied by 16S ribosomal ribonucleic acid (rRNA) gene amplicon sequencing and compared to that of 19 healthy controls and 43 controls with Crohn’s disease. Data on intestinal symptoms, diet and quality of life were collected.

Results

Patients with CLD had increased abundances of Proteobacteria, Veillonella, and Prevotella, and lower abundances of normally dominant taxa Ruminococcaceae and Lachnospiraceae when compared with healthy controls and Crohn´s disease. No major differences in fecal microbiota were found between CLD and CLD-associated IBD (including two with yet untreated IBD). Butyrate was poorly tolerated and showed no major effects on fecal microbiota or biomarkers in CLD.

Conclusions

Fecal microbiota in CLD is different from that of healthy subjects or Crohn´s disease. Unexpectedly, no changes in the microbiota or fecal markers characterized CLD-associated IBD, an entity with high frequency among patients with CLD.

Mechanistic basis and preliminary practice of butyric acid and butyrate sodium to mitigate gut inflammatory diseases: a comprehensive review

A key event featured in the early stage of chronic gut inflammatory diseases is the disordered recruitment and excess accumulation of immune cells in the gut lamina propria. This process is followed by the over-secretion of pro-inflammatory factors and the prolonged overactive inflammatory responses. Growing evidence has suggested that gut inflammatory diseases may be mitigated by butyric acid (BA) or butyrate sodium (NaB). Laboratory studies show that BA and NaB can enhance gut innate immune function through G-protein-mediated signaling pathways while mitigating the overactive inflammatory responses by inhibiting histone deacetylase. The regulatory effects may occur in both epithelial enterocytes and the immune cells in the lamina propria. Prior to further clinical trials, comprehensive literature reviews and rigid examination concerning the underlying mechanism are necessary. To this end, we collected and reviewed 197 published reports regarding the mechanisms, bioactivities, and clinical effects of BA and NaB to modulate gut inflammatory diseases. Our review found insufficient evidence to guarantee the safety of clinical practice of BA and NaB, either by anal enema or oral administration of capsule or tablet. The safety of clinical use of BA and NaB should be further evaluated. Alternatively, dietary patterns rich in "fruits, vegetables and beans" may be an effective and safe approach to prevent gut inflammatory disease, which elevates gut microbiota-dependent production of BA. Our review provides a comprehensive reference to future clinical trials of BA and NaB to treat gut inflammatory diseases.

Congenital chloride diarrhea clinical features and management: a systematic review

INTRODUCTION

Congenital chloride diarrhea (CLD) is a rare autosomal recessive disorder characterized by watery diarrhea with a high level of fecal Cl^-, metabolic alkalosis, and electrolyte alterations. Several intestinal and extraintestinal complications and even death can occur. An optimal knowledge of the clinical features and best therapeutic strategies is mandatory for an effective management.

METHODS

Articles published between 1 January 1965 and 31 December 2019, reported in PUBMED and EMBASE, were evaluated for a systematic review analyzing four categories: anamnestic features, clinical features, management, and follow-up strategies.

RESULTS

Fifty-seven papers reporting information on 193 CLD patients were included. The most common anamnestic features were positive family anamnesis for chronic diarrhea (44.4%), consanguinity (75%), polyhydramnios (98.3%), preterm delivery (78.6%), and failure to pass meconium (60.7%). Mean age at diarrhea onset was 6.63 days. Median diagnostic delay was 60 days. Prenatal diagnosis, based on molecular analysis, was described in 40/172 (23.3%). All patients received NaCl/KCl-substitutive therapy. An improvement of diarrhea during adulthood was reported in 91.3% of cases. Failure to thrive (21.6%) and chronic kidney disease (17.7%) were the most common complications.

CONCLUSIONS

This analysis of a large population suggests the necessity of better strategies for the management of CLD. A close follow-up and a multidisciplinary approach is mandatory to manage this condition characterized by heterogeneous and multisystemic complications.

IMPACT

In this systematic review, we describe data regarding anamnestic features, clinical features, management, and follow-up of CLD patients obtained from the largest population of patients ever described to date. The results of our investigation could provide useful insights for the diagnostic approach and the management of this condition.

NGS Gene Panel Analysis Revealed Novel Mutations in Patients with Rare Congenital Diarrheal Disorders

Congenital diarrheal disorders (CDDs) are early-onset enteropathies generally inherited as autosomal recessive traits. Most patients with CDDs require rapid diagnosis as they need immediate and specific therapy to avoid a poor prognosis, but their clinical picture is often overlapping with a myriad of nongenetic diarrheal diseases. We developed a next-generation sequencing (NGS) panel for the analysis of 92 CDD-related genes, by which we analyzed patients suspect for CDD, among which were (i) three patients with sucrose-isomaltase deficiency; (ii) four patients with microvillous inclusion disease; (iii) five patients with congenital tufting enteropathy; (iv) eight patients with glucose-galactose malabsorption; (v) five patients with congenital chloride diarrhea. In all cases, we identified the mutations in the disease-gene, among which were several novel mutations for which we defined pathogenicity using a combination of bioinformatic tools. Although CDDs are rare, all together, they have an incidence of about 1%. Considering that the clinical picture of these disorders is often confusing, a CDD-related multigene NGS panel contributes to unequivocal and rapid diagnosis, which also reduces the need for invasive procedures.

Step-Up Approach for Sodium Butyrate Treatment in Children With Congenital Chloride Diarrhea

OBJECTIVES

Oral salt substitutive therapy is pivotal for the survival of patients with congenital chloride diarrhea (CLD), however this therapy is unable to influence the symptoms severity. Butyrate has been proposed to limit diarrhea severity in CLD. Unfortunately, the optimal dose schedule is still largely undefined. In addition, butyrate seems not to be well-tolerated by all patients, with some subjects reporting diarrhea worsening. We investigated the efficacy of a step-up therapeutic approach with sodium butyrate in patients who experienced a diarrhea worsening or an absent improvement after the direct administration of 100 mg/kg/day of sodium butyrate.

METHODS

The efficacy of a step-up therapeutic approach starting from 50 mg/Kg/day with a subsequent 25 mg/kg/day weekly increase up to 100 mg/kg/day of oral sodium butyrate was investigated in previously three unresponsive CLD children.

RESULTS

The step-up therapeutic approach resulted effective in limiting diarrhea severity in all our three previously unresponsive CLD patients.

CONCLUSIONS

Our results suggest the efficacy of the step-up therapeutic approach in CLD children.

Pharmacological and Parenteral Nutrition-Based Interventions in Microvillus Inclusion Disease

Microvillus inclusion disease (MVID) is a rare inherited and invariably fatal enteropathy, characterized by severe intractable secretory diarrhea and nutrient malabsorption. No cure exists, and patients typically die during infancy because of treatment-related complications. The need for alternative treatment strategies is evident. Several pharmacological interventions with variable successes have been tried and reported for individual patients as part of their clinical care. Unfortunately, these interventions and their outcomes have remained hidden in case reports and have not been reviewed. Further, recent advances regarding MVID pathogenesis have shed new light on the outcomes of these pharmacological interventions and offer suggestions for future clinical research and trials. Hence, an inventory of reported pharmacological interventions in MVID, their rationales and outcomes, and a discussion of these in the light of current knowledge is opportune. Together with a discussion on MVID-specific pharmacokinetic, -dynamic, and -genetic concerns that pose unique challenges regarding pharmacological strategies, we envision that this paper will aid researchers and clinicians in their efforts to develop pharmacological interventions to combat this devastating disease.

Impaired Ratio of Unsaturated to Saturated Non-Esterified Fatty Acids in Saliva from Patients with Cystic Fibrosis

Impaired salivary non-esterified fatty acids (NEFA) levels have been previously observed in cystic fibrosis (CF). This study aimed to characterize the salivary NEFA profile in CF and to examine whether the alterations are related to the pancreatic status and/or lung disease severity. We analyzed salivary NEFA, cholesterol and interleukin-6 (IL-6) in CF patients (n = 66) and healthy subjects (n = 48). CF patients showed higher salivary levels of cholesterol, total NEFA (that was negatively correlated with serum triglycerides), unsaturated NEFA/saturated NEFA (U/S NEFA) ratio and IL-6 than controls. The U/S NEFA ratio was positively correlated with IL-6 in both patients and controls, suggesting an association between this parameter and local inflammation independently from the disease. No correlation between salivary lipids and pancreatic status was observed, while the U/S NEFA ratio was higher in patients with severe lung disease than mild/moderate severity and may represent a prognostic marker of lung disease in CF.

Perturbations of the Gut Microbiome and Metabolome in Children with Calcium Oxalate Kidney Stone Disease

BACKGROUND

The relationship between the composition and function of gut microbial communities and early-onset calcium oxalate kidney stone disease is unknown.

METHODS

We conducted a case-control study of 88 individuals aged 4-18 years, which included 44 individuals with kidney stones containing ≥50% calcium oxalate and 44 controls matched for age, sex, and race. Shotgun metagenomic sequencing and untargeted metabolomics were performed on stool samples.

RESULTS

Participants who were kidney stone formers had a significantly less diverse gut microbiome compared with controls. Among bacterial taxa with a prevalence >0.1%, 31 taxa were less abundant among individuals with nephrolithiasis. These included seven taxa that produce butyrate and three taxa that degrade oxalate. The lower abundance of these bacteria was reflected in decreased abundance of the gene encoding butyryl-coA dehydrogenase (P=0.02). The relative abundance of these bacteria was correlated with the levels of 18 fecal metabolites, and levels of these metabolites differed in individuals with kidney stones compared with controls. The oxalate-degrading bacterial taxa identified as decreased in those who were kidney stone formers were components of a larger abundance correlation network that included Eggerthella lenta and several Lactobacillus species. The microbial (α) diversity was associated with age of stone onset, first decreasing and then increasing with age. For the individuals who were stone formers, we found the lowest α diversity among individuals who first formed stones at age 9-14 years, whereas controls displayed no age-related differences in diversity.

CONCLUSIONS

Loss of gut bacteria, particularly loss of those that produce butyrate and degrade oxalate, associates with perturbations of the metabolome that may be upstream determinants of early-onset calcium oxalate kidney stone disease.

Clinical Features, Molecular Genetics, and Long-Term Outcome in Congenital Chloride Diarrhea: A Nationwide Study in Japan

OBJECTIVE

To clarify clinical and genetic features of Japanese children with congenital chloride diarrhea (CCD).

STUDY DESIGN

This was a multi-institutional, retrospective survey of 616 pediatric centers in Japan with identified patients with CCD between 2014 and 2018. Mutations involving SLC26A3 were detected by Sanger sequencing.

RESULTS

Thirteen patients met all entry criteria including mutations in SLC26A3, and 14 patients satisfied clinical diagnostic criteria. Homozygous or compound heterozygous mutations in SLC26A3, including 6 novel mutations, were identified in 13 of these 14 patients (93%). The most common (detected in 7 of 13) was c.2063-1g>t. Median age at diagnosis was 1 day. Nine of the patients meeting all criteria were diagnosed as neonates (69%). Median follow-up duration was 10 years. When studied, 8 patients had <5 stools daily (62%), and all had fewer than in infancy. Only 1 patient had nephrocalcinosis, and 3 (23%) had mild chronic kidney disease. Neurodevelopment was generally good; only 1 patient required special education. Five patients (38%) received long-term sodium, potassium, and chloride supplementation.

CONCLUSIONS

Early fetal ultrasound diagnosis and prompt long-term sodium, potassium, and chloride supplementation were common management features. Genetic analysis of SLC26A3 provided definitive diagnosis of CCD. In contrast with previously reported localities, c.2063-1g>t might be a founder mutation in East Asia.

Congenital chloride losing diarrhea: A single center experience in a highly consanguineous population

Congenital chloride losing diarrhea (CCLD) is a rare type of chronic watery diarrhea due to mutations in SLC26A3 gene leading to defective chloride-bicarbonate exchanges with the resultant loss of chloride and retention of bicarbonate.We aim to define pediatric Saudi CCLD patients' characteristics to achieve prompt diagnosis, management, follow up with good quality of life, and prevention of complications in these patients.We carried retrospective data review of demographic, clinical, laboratory, radiographic, and outcome of all pediatric patients fulfilling the criteria of CCLD over 10 years from 2004 to 2014 from a single center in Taif region, Saudi Arabia.Forty-nine patients fulfilled the criteria of CCLD from 21 families with more than one affected patient in the same family in 90% of them and positive consanguinity in 91% of the cohort. Most patients were born preterm with intrauterine growth restriction and usually neonatal intensive care unit (NICU) admissions with prematurity and its complications. Thirteen patients were discharged without diagnosis of CCLD and 3 were misdiagnosed as intestinal obstruction with unnecessary surgical intervention. Many complications do existed with renal complications being the most common with three patients received renal transplantation.Prematurity with abdominal distension and stool like urine were the commonest presentation of CCLD in Saudi children. Positive consanguinity and more than one affected sibling are present in most of our cohort.High index of suspicion by clinicians is a cornerstone for early diagnosis with subsequent favorable outcome.A multicenter national incidence study of CCLD in KSA and its genetic attributes is recommended. Premarital screening should be implemented specially for consanguineous marriage.

Two cases of microvillous inclusion disease caused by novel mutations in MYO5B gene

Microvillous inclusion disease (MVID) typically appears with severe chronic diarrhea in the few days after birth and rapidly causes dehydration and metabolic acidosis. In this context, presenting two novel cases, we underline the crucial importance of mutation analysis for the diagnosis of this disease that may be easily misdiagnosed.

An "ex vivo model" contributing to the diagnosis and evaluation of new drugs in cystic fibrosis

Cystic fibrosis (CF) is an autosomal recessive disease caused by mutations in the cystic fibrosis transmembrane regulator (CFTR) gene. About 2000 mutations have been described so far. We setup an ex vivo model of human nasal epithelial cells (HNECs) to study CF patients testing the effect of novel mutations and molecular therapies. We performed sampling (by brushing), followed by culture and analysis of HNECs using a series of molecular techniques. We performed 50 brushings from CF patients and controls. Using cultured cells, we: i) demonstrated the widely heterogeneous CFTR expression in patients and in controls; ii) defined the splicing effect of a CFTR mutation; iii) assessed the CFTR gating activity in patients bearing different mutations; iv) demonstrated that butyrate significantly enhances CFTR expression. Based on our data, we can conclude: 1) HNEC brushing is performed without anaesthesia and is well tolerated in all CF patients (children and adults); 2) HNECs can be preserved for up to 48 hours before culture allowings multicentre studies; 3) HNECs culture can be considered a suitable model to study the molecular effects of new CFTR gene mutations and/or uncertain meaning specific mutations of carriers; 4) an ex vivo model of HNECs may be used to evaluate, before human use, the effect of new drugs on patients’ cells bearing specific CFTR mutations; 5) the methodology is adequate for a quantitative measurement, by fluorescence, of the CFTR gating activity of the HNECs from patients with different genotypes identifying: a) CF patients bearing two severe mutations with an activity < 10% (compared to controls – 100%); b) CF patients bearing at least a mild mutation with an activity of 10-20%; c) CF carriers (heterozygous subjects) with an activity between 40-70%.

Butyrate modulating effects on pro-inflammatory pathways in human intestinal epithelial cells

Butyrate acts as energy source for intestinal epithelial cells and as key mediator of several immune processes, modulating gene expression mainly through histone deacetylation inhibition. Thanks to these effects, butyrate has been proposed for the treatment of many intestinal diseases. Aim of this study was to investigate the effect of butyrate on the expression of a large series of target genes encoding proteins involved in pro-inflammatory pathways. We performed quantitative real-time-PCR analysis of the expression of 86 genes encoding proteins bearing to pro-inflammatory pathways, before and after butyrate exposure, in primary epithelial cells derived from human small intestine and colon. Butyrate significantly down-regulated the expression of genes involved in inflammatory response, among which nuclear factor kappa beta, interferon-gamma, Toll like 2 receptor and tumour necrosis factor-alpha. Further confirmations of these data, including studies at protein level, would support the use of butyrate as effective therapeutic strategy in intestinal inflammatory disorders.

Twelve Novel Mutations in the SLC26A3 Gene in 17 Sporadic Cases of Congenital Chloride Diarrhea

OBJECTIVES

We aimed to improve the knowledge of pathogenic mutations in sporadic cases of congenital chloride diarrhea (CCD) and emphasize the importance of functional studies to define the effect of novel mutations.

METHODS

All member 3 of solute carrier family 26 (SLC26A3) coding regions were sequenced in 17 sporadic patients with CCD. Moreover, the minigene system was used to analyze the effect of 2 novel splicing mutations.

RESULTS

We defined the SLC26A3 genotype of all 17 patients with CCD and identified 12 novel mutations. Using the minigene system, we confirmed the in silico prediction of a complete disruption of splicing pattern caused by 2 of these novel mutations: the c.971+3_971+4delAA and c.735+4_c.735+7delAGTA. Moreover, several prediction tools and a structure-function prediction defined the pathogenic role of 6 novel missense mutations.

CONCLUSIONS

We confirm the molecular heterogeneity of sporadic CCD adding 12 novel mutations to the list of known pathogenic mutations. Moreover, we underline the importance, for laboratories that offer molecular diagnosis and genetic counseling, to perform fast functional analysis of novel mutations.

Vitamin A deficiency impacts the structural segregation of gut microbiota in children with persistent diarrhea

To investigate whether gut microbiota is associated with vitamin A nutritional levels in children with persistent diarrhea, a total of 59 pediatric patients with persistent diarrhea aged 1-12 months were selected from the Department of Gastroenterology at the Children's Hospital of Chongqing Medical University, China. Subjects were hospitalized and divided into VA-deficient (n = 30) and VA-normal (n = 29) groups according to their venous serum retinol levels. Fecal samples from all 59 subjects were collected immediately after admission and analyzed by Illumina MiSeq for 16S rRNA genes to characterize the overall microbiota of the samples. The gut microbiota of the VA-deficient and VA-normal groups were compared using a bioinformatic statistical approach. The Shannon index (p = 0.02), Simpson index (p = 0.01) and component diagram data indicated significantly lower diversity in the VA-deficient than the VA-normal group. A metagenome analysis (LEfSe) and a differentially abundant features approach using Metastats revealed that Escherichia coli and Clostridium butyricum were the key phylotypes of the VA-normal group, while Enterococcus predominated the VA-deficient group. In conclusion, the diversity of gut microbiota and the key phylotypes are significantly different in children with persistent diarrhea at different VA nutritional levels.

Congenital intestinal diarrhoeal diseases: A diagnostic and therapeutic challenge

Congenital diarrhoeal disorders are a heterogeneous group of inherited malabsorptive or secretory diseases typically appearing in the first weeks of life, which may be triggered by the introduction of distinct nutrients. However, they may also be unrecognised for a while and triggered by exogenous factors later on. In principle, they can be clinically classified as osmotic, secretory or inflammatory diarrhoea. In recent years the disease-causing molecular defects of these congenital disorders have been identified. According to the underlying pathophysiology they can be classified into four main groups: 1) Defects of digestion, absorption and transport of nutrients or electrolytes 2) Defects of absorptive enterocyte differentiation or polarisation 3) Defects of the enteroendocrine cells 4) Defects of the immune system affecting the intestine. Here, we describe the clinical presentation of congenital intestinal diarrhoeal diseases, the diagnostic work-up and specific treatment aspects.

Congenital diarrhoeal disorders: advances in this evolving web of inherited enteropathies

Congenital diarrhoeal disorders (CDDs) represent an evolving web of rare chronic enteropathies, with a typical onset early in life. In many of these conditions, severe chronic diarrhoea represents the primary clinical manifestation, whereas in others diarrhoea is only a component of a more complex multi-organ or systemic disorder. Typically, within the first days of life, diarrhoea leads to a life-threatening condition highlighted by severe dehydration and serum electrolyte abnormalities. Thus, in the vast majority of cases appropriate therapy must be started immediately to prevent dehydration and long-term, sometimes severe, complications. The number of well-characterized disorders attributed to CDDs has gradually increased over the past several years, and many new genes have been identified and functionally related to CDDs, opening new diagnostic and therapeutic perspectives. Molecular analysis has changed the diagnostic scenario in CDDs, and led to a reduction in invasive and expensive procedures. Major advances have been made in terms of pathogenesis, enabling a better understanding not only of these rare conditions but also of more common diseases mechanisms.

Rare mutation in the SLC26A3 transporter causes life-long diarrhoea with metabolic alkalosis

SLC26A3, a chloride/bicarbonate transporter mainly expressed in the intestines, plays a pivotal role in chloride absorption. We present a 23-year-old woman with a history of congenital chloride diarrhoea (CCD) and renal transplant who was admitted for rehydration and treatment of acute kidney injury after she presented with an acute diarrhoeal episode. Laboratory investigations confirmed metabolic alkalosis and severe hypochloraemia, consistent with her underlying CCD. This contrasts with most other forms of diarrhoea, which are normally associated with metabolic acidosis. Genetic testing was offered and revealed a homozygous non-sense mutation in SLC26A3 (Gly-187-Stop). This loss-of-function mutation results in bicarbonate retention in the blood and chloride loss into the intestinal lumen. Symptomatic management with daily NaCl and KCl oral syrups was supplemented with omeprazole therapy. The loss of her own kidneys is most likely due to crystal-induced nephropathy secondary to chronic volume contraction and chloride depletion. This case summarises the pathophysiology and management of CCD.

Challenging the diagnosis of cystic fibrosis in a patient carrying the 186-8T/C allelic variant in the CF transmembrane conductance regulator gene

Background

This report describe for the first time a clinical case with a CFTR allelic variant 186-8T/C (c.54-8 T/C) in intron 1 of CFTR and underline the importance of applying a combination of genetic and functional tests to establish or exclude a diagnosis of Cystic Fibrosis. In this case the diagnostic algorithm proposed for CF has been successfully applied at our Center and previous CF diagnosis assigned in a different Center was not confirmed.

Case presentation

A 38 year-old Italian woman had been treated as affected by CF since 2010, following diagnosis based on sweat tests (reported values of 73 and 57 mEq/L) and a clinical history consistent with CF. No mutations were identified by first level of genetic analysis. Afterwards the patient referred to our center for assessing the relevance of these findings. The genetic variant 186-8T/C (c.54-8 T/C) in intron 1 of the CFTR gene was detected by sequencing. Low-level interstitial-alveolar infiltration was recorded by high-resolution computerized tomography. Lung function was normal and sputum and Broncho Alveolar Lavage cultures resulted bacteriologically negative. Sweat chloride levels was re-assessed and resulted with values of 57 and 35 mEq/L, with a borderline range between 40 and 60 mEq/L. Nasal Potential Difference measurements resulted in three reliable measurements consistent with a non-CF phenotype. Differential diagnosis with ciliary dyskinesia was excluded, as was exon 2 skipping of CFTR gene that might have caused a CFTR functional defect. Furthermore, single cell fluorescence analysis in response to cAMP agonists performed in patient’s monocytes overlapped those obtained in healthy donors.

Conclusion

We concluded that this patient was not affected by CF. This case highlights the need for referrals to highly specialized centers and the importance of combined functional and genetic tests in making a correct diagnosis. Moreover, we confirmed a correlation between NPD tracings and cell depolarization in monocytes providing a rationale for proposing the use of leukocytes as a potential support for CF diagnosis.