The cystic fibrosis transmembrane conductance regulator gene and ion channel function in patients with idiopathic pancreatitis

ECFS standards of care on CFTR-related disorders: Identification and care of the disorders

This is the third paper in the series providing updated information and recommendations for people with cystic fibrosis transmembrane conductance regulator (CFTR)-related disorder (CFTR-RD). This paper covers the individual disorders, including the established conditions - congenital absence of the vas deferens (CAVD), diffuse bronchiectasis and chronic or acute recurrent pancreatitis - and also other conditions which might be considered a CFTR-RD, including allergic bronchopulmonary aspergillosis, chronic rhinosinusitis, primary sclerosing cholangitis and aquagenic wrinkling. The CFTR functional and genetic evidence in support of the condition being a CFTR-RD are discussed and guidance for reaching the diagnosis, including alternative conditions to consider and management recommendations, is provided. Gaps in our knowledge, particularly of the emerging conditions, and future areas of research, including the role of CFTR modulators, are highlighted.

ECFS standards of care on CFTR-related disorders: Towards a comprehensive program for affected individuals

After three publications defining an updated guidance on the diagnostic criteria for people with cystic fibrosis transmembrane conductance regulator (CFTR)-related disorders (pwCFTR-RDs), establishing its relationship to CFTR-dysfunction and describing the individual disorders, this fourth and last paper in the series addresses some critical challenges facing health care providers and pwCFTR-RD. Topics included are: 1) benefits and obstacles to collect data from pwCFTR-RD are discussed, together with the opportunity to integrate them into established CF-registries; 2) the potential of infants designated CRMS/CFSPID to develop a CFTR-RD and how to communicate this information; 3) a description of the challenges in genetic counseling, with particular regard to phenotypic variability, unknown long-term evolution, CFTR testing and pregnancy termination 4) a proposal for the assessment of potential barriers to the implementation and dissemination of the produced documents to health care professionals involved in the care of pwCFTR-RD and a process to monitor the implementation of the CFTR-RD recommendations; 5) clinical trials investigating the efficacy of CFTR modulators in CFTR-RD and how endpoints and outcomes might be adapted to the heterogeneity of these disorders.

Bicarbonate defective CFTR variants increase risk for chronic pancreatitis: A meta-analysis

INTRODUCTION

Cystic fibrosis transmembrane conductance regulator (CFTR) plays a central role in pancreatic ductal fluid secretion by mediating Cl- and HCO3- ion transport across the apical membrane. Severe CFTR mutations that diminish chloride conductance cause cystic fibrosis (CF) if both alleles are affected, whereas heterozygous carrier status increases risk for chronic pancreatitis (CP). It has been proposed that a subset of CFTR variants characterized by a selective bicarbonate conductance defect (CFTRBD) may be associated with CP but not CF. However, a rigorous genetic analysis of the presumed association has been lacking.

AIMS

To investigate the role of heterozygous CFTRBD variants in CP by meta-analysis of published case-control studies.

MATERIALS AND METHODS

A systematic search was conducted in the MEDLINE, Embase, Scopus, and CENTRAL databases for published studies that reported the CFTRBD variants p.R74Q, p.R75Q, p.R117H, p.R170H, p.L967S, p.L997F, p.D1152H, p.S1235R, and p.D1270N in CP patients and controls.

RESULTS

Twenty-two studies were eligible for quantitative synthesis. Combined analysis of the 9 CFTRBD variants indicated enrichment in CP patients versus controls (OR = 2.31, 95% CI = 1.17-4.56). Individual analysis of CFTRBD variants revealed no association of p.R75Q with CP (OR = 1.12, 95% CI = 0.89-1.40), whereas variants p.R117H and p.L967S were significantly overrepresented in cases relative to controls (OR = 3.16, 95% CI = 1.94-5.14, and OR = 3.88, 95% CI = 1.32-11.47, respectively). The remaining 6 low-frequency variants gave inconclusive results when analyzed individually, however, their pooled analysis indicated association with CP (OR = 2.08, 95% CI = 1.38-3.13).

CONCLUSION

Heterozygous CFTRBD variants, with the exception of p.R75Q, increase CP risk about 2-4-fold.

Surgical considerations in cystic fibrosis: what every general surgeon needs to know

Cystic fibrosis (CF) is a complex multiorgan disease, which often affects the gastrointestinal tract. With improved CF specific therapies and multidisciplinary management, patients with CF are now living longer with a median life expectancy of around 50 years. This increased life expectancy has resulted in corresponding increase in presentations of the CF patient with comorbid surgical conditions that were never important considerations. Investigations and management of these conditions, such as distal intestinal obstruction syndrome and colorectal cancer warrant good clinical understanding of the unique challenges that CF patients present including chronic immunosuppression, impaired respiratory function and their multi-organ dysfunction. The purpose of this review is to provide general surgeons with a contemporary update on the CF related surgical issues as they are likely to become increasingly involved in the care of these complex patients and form an integral part of the multidisciplinary team.

Chronic Pancreatitis: What the Clinician Wants to Know from MR Imaging

Diagnosis of chronic pancreatitis requires a complete medical history and clinical investigations, including imaging technologies and function tests. MR imaging/magnetic resonance cholangiopancreatography is the preferred diagnostic tool for detection of ductal and parenchymal changes in patients with chronic pancreatitis. Ductal changes may not be present in the initial phase of chronic pancreatitis. Therefore, early diagnosis remains challenging.

Trans-heterozygosity for mutations enhances the risk of recurrent/chronic pancreatitis in patients with Cystic Fibrosis

BACKGROUND

Recurrent (RP) and chronic pancreatitis (CP) may complicate Cystic Fibrosis (CF). It is still unknown if mutations in genes involved in the intrapancreatic activation of trypsin (IPAT) or in the pancreatic secretion pathway (PSP) may enhance the risk for RP/CP in patients with CF.

METHODS

We enrolled: 48 patients affected by CF complicated by RP/CP and, as controls 35 patients with CF without pancreatitis and 80 unrelated healthy subjects. We tested a panel of 8 genes involved in the IPAT, i.e. PRSS1, PRSS2, SPINK1, CTRC, CASR, CFTR, CTSB and KRT8 and 23 additional genes implicated in the PSP.

RESULTS

We found 14/48 patients (29.2%) with mutations in genes involved in IPAT in the group of CF patients with RP/CP, while mutations in such genes were found in 2/35 (5.7%) patients with CF without pancreatitis and in 3/80 (3.8%) healthy subjects (p < 0.001). Thus, we found mutations in 12 genes of the PSP in 11/48 (22.9%) patients with CF and RP/CP. Overall, 19/48 (39.6%) patients with CF and RP/CP showed one or more mutations in the genes involved in the IPAT and in the PSP while such figure was 4/35 (11.4%) for patients with CF without pancreatitis and 11/80 (13.7%) for healthy controls (p < 0.001).

CONCLUSIONS

The trans-heterozygous association between CFTR mutations in genes involved in the pathways of pancreatic enzyme activation and the pancreatic secretion may be risk factors for the development of recurrent or chronic pancreatitis in patients with CF.

Brushed nasal epithelial cells are a surrogate for bronchial epithelial CFTR studies

Recent advances in the management of cystic fibrosis (CF) target underlying defects in the CF transmembrane conductance regulator (CFTR) protein, but efficacy analyses remain limited to specific genotype-based subgroups. Patient-derived model systems may therefore aid in expanding access to these drugs. Brushed human nasal epithelial cells (HNEs) are an attractive tissue source, but it remains unclear how faithfully they recapitulate human bronchial epithelial cell (HBE) CFTR activity. We examined this gap using paired, brushed HNE/HBE samples from pediatric CF subjects with a wide variety of CFTR mutations cultured at the air-liquid interface. Growth and structural characteristics for the two cell types were similar, including differentiation into mature respiratory epithelia. In electrophysiologic analysis, no correlation was identified between nasal and bronchial cultures in baseline resistance or epithelial sodium channel (ENaC) activity. Conversely, robust correlation was demonstrated between nasal and bronchial cultures in both stimulated and inhibited CFTR activity. There was close correlation in modulator-induced change in CFTR activity, and CFTR activity in both cell types correlated with in vivo sweat chloride measurements. These data confirm that brushed HNE cell cultures recapitulate the functional CFTR characteristics of HBEs with fidelity and are therefore an appropriate noninvasive HBE surrogate for individualized CFTR analysis.

V232D mutation in patients with cystic fibrosis: Not so rare, not so mild

The frequency of some Cystic Fibrosis (CF) Transmembrane Conductance Regulator gene (CFTR) mutations varies between populations. Genetic testing during newborn screening (NBS) for CF can identify less common mutations with low clinical expression in childhood and previously considered mild but not fully characterized, such as the mutation p.Val232Asp (c.695T > A). The aim of this study was to describe CF patients with the V232D mutation. We identify CF children with the V232D mutation detected by NBS and compare them with CF adults with this mutation whose diagnosis was prompted by clinical symptoms in the same period. We studied clinical, biochemical, spirometric, and prognostic features in both populations. NBS program tested 276,523 children during a period of 14 years (2003-2017) and identified 54 cases of CF. Six children (11%) had the V232D mutation. Over the same period, 5 adults (age 37.6 ± 16.29 years old) with symptoms of CF and this mutation were also diagnosed. Follow-up duration was mean 10.1 years for adults and mean 6.5 years for children. In the adult group, lung function was impaired at diagnosis in all patients (Forced Expiratory Volume1-FEV1-67.12% ± 13.09) and worsened in children tested during evolution (FEV1first: 113%; FEV1last: 64%). Pancreatic insufficiency was present in adult group, with recurrent pancreatitis in 1 present. Although with less clinical expression in children, V232D is associated with pulmonary and pancreatic involvement during adulthood and CF cannot be considered mild. This mutation is present in 11% of all patients diagnosed with CF in our region. Its inclusion in some NBS programs should be taken into account in order to improve the prognosis of affected children.

Stem cell-derived organoids to model gastrointestinal facets of cystic fibrosis

Cystic fibrosis (CF) is one of the most frequently occurring inherited human diseases caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) which lead to ample defects in anion transport and epithelial fluid secretion. Existing models lack both access to early stages of CF development and a coeval focus on the gastrointestinal CF phenotypes, which become increasingly important due increased life span of the affected individuals. Here, we provide a comprehensive overview of gastrointestinal facets of CF and the opportunity to model these in various systems in an attempt to understand and treat CF. A particular focus is given on forward-leading organoid cultures, which may circumvent current limitations of existing models and thereby provide a platform for drug testing and understanding of disease pathophysiology in gastrointestinal organs.

Diagnosis of Cystic Fibrosis in Nonscreened Populations

OBJECTIVE

Although the majority of cases of cystic fibrosis (CF) are now diagnosed through newborn screening, there is still a need to standardize the diagnostic criteria for those diagnosed outside of the neonatal period. This is because newborn screening started relatively recently, it is not performed everywhere, and even for individuals who were screened, there is the possibility of a false negative. To limit irreversible organ pathology, a timely diagnosis of CF and institution of CF therapies can greatly benefit these patients.

STUDY DESIGN

Experts on CF diagnosis were convened at the 2015 CF Foundation Diagnosis Consensus Conference. The participants reviewed and discussed published works and instructive cases of CF diagnosis in individuals presenting with signs, symptoms, or a family history of CF. Through a modified Delphi methodology, several consensus statements were agreed upon. These consensus statements were updates of prior CF diagnosis conferences and recommendations.

RESULTS

CF diagnosis in individuals outside of newborn screening relies on the clinical evidence and on evidence of CF transmembrane conductance regulator (CFTR) dysfunction. Clinical evidence can include typical organ pathologies seen in CF such as bronchiectasis or pancreatic insufficiency but often represent a broad range of severity including mild cases. CFTR dysfunction can be demonstrated using sweat chloride testing, CFTR molecular genetic analysis, or CFTR physiologic tests. On the basis of the large number of patients with bona fide CF currently followed in registries with sweat chloride levels between 30 and 40 mmol/L, the threshold considered "intermediate" was lowered from 40 mmol/L in the prior diagnostic guidelines to 30 mmol/L. The CF diagnosis was also discussed in the context of CFTR-related disorders in which CFTR dysfunction may be present, but the individual does not meet criteria for CF.

CONCLUSIONS

CF diagnosis remains a rare but important condition that can be diagnosed when characteristic clinical features are seen in an individual with demonstrated CFTR dysfunction.

Causal Evaluation of Acute Recurrent and Chronic Pancreatitis in Children: Consensus From the INSPPIRE Group

OBJECTIVES

Acute recurrent pancreatitis (ARP) and chronic pancreatitis (CP) have been diagnosed in children at increasing rates during the past decade. As pediatric ARP and CP are still relatively rare conditions, little quality evidence is available on which to base the diagnosis and determination of etiology. The aim of the study was to review the current state of the literature regarding the etiology of these disorders and to developed a consensus among a panel of clinically active specialists caring for children with these disorders to help guide the diagnostic evaluation and identify areas most in need of future research.

METHODS

A systematic review of the literature was performed and scored for quality, followed by consensus statements developed and scored by each individual in the group for level of agreement and strength of the supporting data using a modified Delphi method. Scores were analyzed for the level of consensus achieved by the group.

RESULTS

The panel reached consensus on 27 statements covering the definitions of pediatric ARP and CP, evaluation for potential etiologies of these disorders, and long-term monitoring. Statements for which the group reached consensus to make no recommendation or could not reach consensus are discussed.

CONCLUSIONS

This consensus helps define the minimal diagnostic evaluation and monitoring of children with ARP and CP. Even in areas in which we reached consensus, the quality of the evidence is weak, highlighting the need for further research. Improved understanding of the underlying cause will facilitate treatment development and targeting.

Comparison of Nasal Potential Difference and Intestinal Current Measurements as Surrogate Markers for CFTR Function

OBJECTIVES

Nasal potential difference (NPD) measurement is part of the diagnostic criteria for cystic fibrosis (CF) and now used routinely as an endpoint in clinical trials of correcting the basic defect in CF. Intestinal current measurement (ICM), measured ex vivo on a rectal biopsy, has been used to study cystic fibrosis transmembrane conductance regulator (CFTR) function but has not been compared to NPD in the same subject in adults and children. The aim of the study is to evaluate the potential usefulness of ICM as a marker of CFTR function for treatment studies compared NPD in patients with CF and in healthy control subjects.

METHODS

ICM and NPD were performed on healthy controls and patients with CF. The healthy adults were individuals undergoing routine screening colonoscopy at the Beth Israel Deaconess Medical Center. The healthy children were undergoing colonoscopy for suspicion of inflammation in Hadassah Hebrew University Medical Center. The CF adults were recruited from Boston Children's Hospital CF Center and CF Center Worcester Mass, the children with CF from Hadassah CF Center.

RESULTS

ICM measurements in healthy control subjects (n = 16) demonstrated a mean (±SE) carbachol response of 16.0 (2.2) μA/cm, histamine response of 13.2 (2.1) μA/cm and a forskolin response of 6.3 (2.0) μA/cm. Basal NPD of -15.9 (1.9) and response to Cl free + isoproterenol of -13.8 (2.0). These responses were inverted in CF subjects (n = 12) for ICM parameters with carbachol response of -3.0 (0.5) μA/cm, histamine -1.0 (0.8) μA/cm and a forskolin response of 0.5 (0.3) and also for NPD parameters; basal NPD of -42.2 (4.3) and response to Cl free + isoproterenol of 4.3 (0.7). Pearson correlation test showed the comparability of ICM and NPD in assessing CFTR function.

CONCLUSIONS

ICM is equivalent to NPD in the ability to distinguish patients with CF from controls and could be used as surrogate markers of CFTR activity in treatment protocols.

Extensive molecular analysis suggested the strong genetic heterogeneity of idiopathic chronic pancreatitis

Rationale: Genetic features of Chronic Pancreatitis (CP) have been extensively investigated mainly testing genes associated to the trypsinogen activation pathway. However, different molecular pathways involving other genes may be implicated in CP pathogenesis. Objectives: 80 patients with Idiopathic CP were investigated using Next Generation Sequencing approach with a panel of 70 genes related to six different pancreatic pathways: premature activation of trypsinogen; modifier genes of Cystic Fibrosis phenotype; pancreatic secretion and ion homeostasis; Calcium signalling and zymogen granules exocytosis; autophagy; autoimmune pancreatitis related genes. Results: We detected mutations in 34 out of 70 genes examined; 64/80 patients (80.0%) were positive for mutations in one or more genes, 16/80 patients (20.0%) had no mutations. Mutations in CFTR were detected in 32/80 patients (40.0%) and 22 of them exhibited at least one mutation in genes of other pancreatic pathways. Of the remaining 48 patients, 13/80 (16.3%) had mutations in genes involved in premature activation of trypsinogen and 19/80 (23.8%) had mutations only in genes of the other pathways: 38/64 patients positive for mutations showed variants in two or more genes (59.3%). Conclusions: Our data, although to be extended with functional analysis of novel mutations, suggest a high rate of genetic heterogeneity in chronic pancreatitis and that trans-heterozygosity may predispose to the idiopathic CP phenotype.

Chronic Pancreatitis: Landmark Papers, Management Decisions, and Future

On May 16, 2015 at the invitation of the American Gastroenterological Association Institute Council E.P.D. presented a state-of-the-art lecture at Digestive Disease Week 2015. The aims were to discuss a selection of landmark papers in chronic pancreatitis (CP) that influence modern management and to conclude by suggesting some future directions. This is based on that presentation. We will specifically review the following: duct anatomy and pancreas divisum, description of chronic relapsing pancreatitis and its differentiation from recurrent acute pancreatitis and established CP (ECP), natural histories and gene discoveries of alcoholic, idiopathic and hereditary pancreatitis, development of pancreatic cancer in CP, exocrine pancreatic insufficiency and calculation of dose and delivery of enzymes, endoscopic ultrasonography, and autoimmune pancreatitis. With some exceptions, we exclude basic science and surgery.

CFTR: A New Horizon in the Pathomechanism and Treatment of Pancreatitis

Cystic fibrosis transmembrane conductance regulator (CFTR) is an ion channel that conducts chloride and bicarbonate ions across epithelial cell membranes. Mutations in the CFTR gene diminish the ion channel function and lead to impaired epithelial fluid transport in multiple organs such as the lung and the pancreas resulting in cystic fibrosis. Heterozygous carriers of CFTR mutations do not develop cystic fibrosis but exhibit increased risk for pancreatitis and associated pancreatic damage characterized by elevated mucus levels, fibrosis, and cyst formation. Importantly, recent studies demonstrated that pancreatitis causing insults, such as alcohol, smoking, or bile acids, strongly inhibit CFTR function. Furthermore, human studies showed reduced levels of CFTR expression and function in all forms of pancreatitis. These findings indicate that impairment of CFTR is critical in the development of pancreatitis; therefore, correcting CFTR function could be the first specific therapy in pancreatitis. In this review, we summarize recent advances in the field and discuss new possibilities for the treatment of pancreatitis.

Genetic analysis of the bicarbonate secreting anion exchanger SLC26A6 in chronic pancreatitis

BACKGROUND

Pancreatic ductal HCO3(-) secretion is critically dependent on the cystic fibrosis transmembrane conductance regulator chloride channel (CFTR) and the solute-linked carrier 26 member 6 anion transporter (SLC26A6). Deterioration of HCO3(-) secretion is observed in chronic pancreatitis (CP), and CFTR mutations increase CP risk. Therefore, SLC26A6 is a reasonable candidate for a CP susceptibility gene, which has not been investigated in CP patients so far.

METHODS

As a first screening cohort, 106 subjects with CP and 99 control subjects with no pancreatic disease were recruited from the Hungarian National Pancreas Registry. In 60 non-alcoholic CP cases the entire SLC26A6 coding region was sequenced. In the Hungarian cohort variants c.616G > A (p.V206M) and c.1191C > A (p.P397=) were further genotyped by restriction fragment length polymorphism analysis. In a German replication cohort all exons were sequenced in 40 non-alcoholic CP cases and variant c.616G > A (p.V206M) was further analyzed by sequencing in 321 CP cases and 171 controls.

RESULTS

Sequencing of the entire coding region revealed four common variants: intronic variants c.23 + 78_110del, c.183-4C > A, c.1134 + 32C > A, and missense variant c.616G > A (p.V206M) which were found in linkage disequilibrium indicating a conserved haplotype. The distribution of the haplotype did not show a significant difference between patients and controls in the two cohorts. A synonymous variant c.1191C > A (p.P397=) and two intronic variants c.1248 + 9_20del and c.-10C > T were detected in single cases.

CONCLUSION

Our data show that SLC26A6 variants do not alter the risk for the development of CP.

Genetic and electrophysiological characteristics of recurrent acute pancreatitis

OBJECTIVES

The aim was to present the workup of patients with acute recurrent pancreatitis (ARP) for genetic analysis and electrophysiological testing.

METHODS

Patients with ARP with unknown etiology were referred for genetic testing and evaluation of cystic fibrosis transmembrane conductor regulator (CFTR) function by nasal potential difference (NPD) testing.

RESULTS

A total of 67 patients were evaluated. The mean age was 23 ± 17 years (median 17.0 years, range 1.5-72 years); 90% were Jewish and 10% Arab. Ten (15%) patients carried PRSS1 gene mutation (K23R(7), R122H(2), and D21A(1)). One patient had K172E/- (chymotrypsin C [CTRC]) mutation, 1 had I42M (serine protease inhibitor Kazal type 1 [SPINK1])/V235I (CTRC) together with ΔF508/5T, 1 patient had R67H (SPINK1)/V235I (CTRC), and 1 patient had V235I (CTRC)/-. Ten of 67 (15%) patients submitted for CFTR gene testing carried mutations (ΔF508/L997F, ΔF508/5T(11TG), W1282/5T(12TG), W1282X/Y1014C, ΔF508/R31C, R117H/-, R117H/Y1014C, D1152H/-, 5T(11TG)/-, and L997F/-). Fifty-four (80%) patients underwent sweat testing. Of these, 5 had sweat chloride ≥60 mEq/L, and 22 patients had sweat chloride from 40 to 60 mEq/L. Of the 56 (83%) patients had nasal potential difference testing, 4 (6%) with abnormal results.

CONCLUSIONS

One-third (34%) of patients with ARP carry mutations for hereditary pancreatitis including rare mutations (K23R), and 12.5% have evidence of cftr mutations and 10% had CFTR dysfunction underscoring the importance of genetic and functional workup of these patients.

Benign outcome among positive cystic fibrosis newborn screen children with non-CF-causing variants

BACKGROUND

The Clinical and Functional Translation of CFTR project (CFTR2) classified some cystic fibrosis transmembrane conductance regulator (CFTR) gene variants as non-cystic fibrosis (CF)-causing. To evaluate this, the clinical status of children carrying these mutations was examined.

METHODS

We analyzed CF disease-defining variables over 2-6 years in two groups of California CF screen- positive neonates born from 2007 to 2011: (1) children with two CF-causing variants and (2) children with one CF-causing and one non-CF-causing variant, as defined by CFTR2.

RESULTS

Children carrying non-CF-causing variants had significantly higher birth weight, lower immunoreactive trypsinogen and sweat chloride values, higher first year growth curves, and a lower rate of persistent Pseudomonas aeruginosa colonization compared to children with two CF-causing variants.

CONCLUSIONS

The outcomes in children 2-6 years of age with the L997F, G576A, R1162L, V754M, R668C, R31C, and S1235R variants are consistent with the CFTR2 non-CF-causing classification.

Animal models of gastrointestinal and liver diseases. Animal models of cystic fibrosis: gastrointestinal, pancreatic, and hepatobiliary disease and pathophysiology

Multiple organ systems, including the gastrointestinal tract, pancreas, and hepatobiliary systems, are affected by cystic fibrosis (CF). Many of these changes begin early in life and are difficult to study in young CF patients. Recent development of novel CF animal models has expanded opportunities in the field to better understand CF pathogenesis and evaluate traditional and innovative therapeutics. In this review, we discuss manifestations of CF disease in gastrointestinal, pancreatic, and hepatobiliary systems of humans and animal models. We also compare the similarities and limitations of animal models and discuss future directions for modeling CF.

Cystic fibrosis: an update for clinicians. Part 2: hepatobiliary and pancreatic manifestations

This paper, the second in the series, will build on the first and explore the importance of liver and pancreatic manifestations of cystic fibrosis (CF) and the effect on morbidity and mortality of this multifaceted genetic condition. It will also further develop the critical role of the gastroenterologist as part of the multidisciplinary group of clinicians and allied health staff in the effective management of patients with CF.

Sweat chloride as a biomarker of CFTR activity: proof of concept and ivacaftor clinical trial data

BACKGROUND

We examined data from a Phase 2 trial {NCT00457821} of ivacaftor, a CFTR potentiator, in cystic fibrosis (CF) patients with aG551D mutation to evaluate standardized approaches to sweat chloride measurement and to explore the use of sweat chloride and nasal potential difference (NPD) to estimate CFTR activity.

METHODS

Sweat chloride and NPD were secondary endpoints in this placebo-controlled, multicenter trial. Standardization of sweat collection, processing,and analysis was employed for the first time. Sweat chloride and chloride ion transport (NPD) were integrated into a model of CFTR activity.

RESULTS

Within-patient sweat chloride determinations showed sufficient precision to detect differences between dose-groups and assess ivacaftor treatment effects. Analysis of changes in sweat chloride and NPD demonstrated that patients treated with ivacaftor achieved CFTR activity equivalent to approximately 35%–40% of normal.

CONCLUSIONS

Sweat chloride is useful in multicenter trials as a biomarker of CFTR activity and to test the effect of CFTR potentiators.

Nasal potential difference: Best or average result for CFTR function as diagnostic criteria for cystic fibrosis?

BACKGROUND

The current practice of averaging the nasal potential difference (NPD) results of right and left nostril measurements reduce inter-individual variability but may underestimate individual CFTR function.

METHODS

Best NPD response to Cl(-)-free and isoproterenol perfusion (=largest ΔPD(0Cl/Iso)) from the right and left nostril was compared to the average result in 13 cystic fibrosis (CF), 78 query-CF patients and 22 healthy controls from 2 cohorts.

RESULTS

Despite moderate to good correlation (p<0.001) between right and left measured ΔPD(0Cl/Iso), we observed large differences in some individuals. A comparison of average versus best ΔPD(0Cl/Iso) showed only moderate agreement (Giessen κ=0.538; Toronto κ=0.607). Averaging ΔPD(0Cl/Iso) showed a lower composite chloride response compared to best ΔPD(0Cl/Iso) and altered diagnostic NPD interpretation in 30 of 113 (27%) subjects.

CONCLUSIONS

The current practice of averaging the NPD results of right and left nostril measurements leads to an underestimation of the individual CFTR function and should be reconsidered.

In vivo readout of CFTR function: ratiometric measurement of CFTR-dependent secretion by individual, identifiable human sweat glands

To assess CFTR function in vivo, we developed a bioassay that monitors and compares CFTR-dependent and CFTR-independent sweat secretion in parallel for multiple (~50) individual, identified glands in each subject. Sweating was stimulated by intradermally injected agonists and quantified by optically measuring spherical sweat bubbles in an oil-layer that contained dispersed, water soluble dye particles that partitioned into the sweat bubbles, making them highly visible. CFTR-independent secretion (M-sweat) was stimulated with methacholine, which binds to muscarinic receptors and elevates cytosolic calcium. CFTR-dependent secretion (C-sweat) was stimulated with a β-adrenergic cocktail that elevates cytosolic cAMP while blocking muscarinic receptors. A C-sweat/M-sweat ratio was determined on a gland-by-gland basis to compensate for differences unrelated to CFTR function, such as gland size. The average ratio provides an approximately linear readout of CFTR function: the heterozygote ratio is ~0.5 the control ratio and for CF subjects the ratio is zero. During assay development, we measured C/M ratios in 6 healthy controls, 4 CF heterozygotes, 18 CF subjects and 4 subjects with 'CFTR-related' conditions. The assay discriminated all groups clearly. It also revealed consistent differences in the C/M ratio among subjects within groups. We hypothesize that these differences reflect, at least in part, levels of CFTR expression, which are known to vary widely. When C-sweat rates become very low the C/M ratio also tended to decrease; we hypothesize that this nonlinearity reflects ductal fluid absorption. We also discovered that M-sweating potentiates the subsequent C-sweat response. We then used potentiation as a surrogate for drugs that can increase CFTR-dependent secretion. This bioassay provides an additional method for assessing CFTR function in vivo, and is well suited for within-subject tests of systemic, CFTR-directed therapeutics.

Does extensive genotyping and nasal potential difference testing clarify the diagnosis of cystic fibrosis among patients with single-organ manifestations of cystic fibrosis?

BACKGROUND

The phenotypic spectrum of cystic fibrosis (CF) has expanded to include patients affected by single-organ diseases. Extensive genotyping and nasal potential difference (NPD) testing have been proposed to assist in the diagnosis of CF when sweat testing is inconclusive. However, the diagnostic yield of extensive genotyping and NPD and the concordance between NPD and the sweat test have not been carefully evaluated.

METHODS

We evaluated the diagnostic outcomes of genotyping (with 122 mutations included as disease causing), sweat testing and NPD in a prospectively ascertained cohort of undiagnosed patients who presented with chronic sino-pulmonary disease (RESP), chronic/recurrent pancreatitis (PANC) or obstructive azoospermia (AZOOSP).

RESULTS

202 patients (68 RESP, 42 PANC and 92 AZOOSP) were evaluated; 17.3%, 22.8% and 59.9% had abnormal, borderline and normal sweat chloride results, respectively. Only 17 (8.4%) patients were diagnosable as having CF by genotyping. Compared to sweat testing, NPD identified more patients as having CF (33.2%) with fewer borderline results (18.8%). The level of agreement according to kappa statistics (and the observed percentage of agreement) between sweat chloride and NPD in RESP, PANC and AZOOSP subjects was 'moderate' (65% observed agreement), 'poor' (33% observed agreement) and 'fair' (28% observed agreement), respectively. The degree of agreement only improved marginally when subjects with borderline sweat chloride results were excluded from the analysis.

CONCLUSIONS

The diagnosis of CF or its exclusion is not always straightforward and may remain elusive even with comprehensive evaluation, particularly among individuals who present at an older age with single-organ manifestations suggestive of CF.

Defining the accuracy of secretin pancreatic function testing in patients with suspected early chronic pancreatitis

OBJECTIVES

The diagnosis of chronic pancreatitis in patients with characteristic symptoms but normal pancreatic imaging is challenging. Assessment of pancreatic function through secretin pancreatic function testing (SPFT) has been advocated in this setting, but its diagnostic accuracy is not fully known.

METHODS

This was a retrospective review of patients who received SPFT at our tertiary care institution between January 1995 and December 2008 for suspected chronic pancreatitis. For all patients, medical records were reviewed for evidence of subsequent development of chronic pancreatitis by imaging and/or pathology. Patients were then categorized as "true positive" or "true negative" for chronic pancreatitis based on follow-up imaging or histologic evidence.

RESULTS

In all, 116 patients underwent SPFT. Of the 27 patients who tested positive, 7 were lost to follow-up. Of the remaining 20 SPFT-positive patients, 9 (45%) developed radiologic or histologic evidence of chronic pancreatitis after a median of 4 years (1-11 years). Of the 89 patients who had negative SPFT testing, 19 were lost to follow-up. Of the remaining 70 patients, 2 were eventually diagnosed with chronic pancreatitis based on subsequent imaging/histology after a median follow-up period of 7 years (3-11 years). The sensitivity of the SPFT in diagnosing chronic pancreatitis was 82% with a specificity of 86%. The positive predictive value (PPV) of chronic pancreatitis was 45% with a negative predictive value (NPV) of 97%.

CONCLUSIONS

In patients with suspected early chronic pancreatitis and normal pancreatic imaging, SPFT is highly accurate at ruling out early chronic pancreatitis with a NPV of 97%.

The cystic fibrosis of exocrine pancreas

The cystic fibrosis transmembrane conductance regulator (CFTR) protein is highly expressed in the pancreatic duct epithelia and permits anions and water to enter the ductal lumen. This results in an increased volume of alkaline fluid allowing the highly concentrated proteins secreted by the acinar cells to remain in a soluble state. This work will expound on the pathophysiology and pathology caused by the malfunctioning CFTR protein with special reference to ion transport and acid-base abnormalities both in humans and animal models. We will also discuss the relationship between cystic fibrosis (CF) and pancreatitis, and outline present and potential therapeutic approaches in CF treatment relevant to the pancreas.

Cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations in pancreatitis

BACKGROUND

The pancreas is one of the primary organs affected by dysfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) protein. While exocrine pancreatic insufficiency is a well-recognized complication of cystic fibrosis (CF), symptomatic pancreatitis is often under-recognized.

RESULTS

The aim of this review is to provide a general overview of CFTR mutation-associated pancreatitis, which affects patients with pancreatic sufficient CF, CFTR-related pancreatitis, and idiopathic pancreatitis. The current hypothesis regarding the role of CFTR dysfunction in the pathogenesis of pancreatitis, and concepts on genotype-phenotype correlations between CFTR and symptomatic pancreatitis will be reviewed. Symptomatic pancreatitis occurs in 20% of pancreatic sufficient CF patients. In order to evaluate genotype-phenotype correlations, the Pancreatic Insufficiency Prevalence (PIP) score was developed and validated to determine severity in a large number of CFTR mutations. Specific CFTR genotypes are significantly associated with pancreatitis. Patients who carry genotypes with mild phenotypic effects have a greater risk of developing pancreatitis than patients carrying genotypes with moderate-severe phenotypic consequences at any given time.

CONCLUSIONS

The genotype-phenotype correlation in pancreatitis is unique compared to other organ manifestations but still consistent with the complex monogenic nature of CF. Paradoxically, genotypes associated with otherwise mild phenotypic effects have a greater risk for causing pancreatitis; compared with genotypes associated with moderate to severe disease phenotypes. Greater understanding into the underlying mechanisms of disease is much needed. The emergence of CFTR-assist therapies may potentially play a future role in the treatment of CFTR-mutation associated pancreatitis.

Genetic prevalence and characteristics in children with recurrent pancreatitis

AIMS

The causes of chronic (CP) and recurrent acute pancreatitis (RAP) in children include anatomic abnormalities and hereditary, metabolic, and autoimmune disorders, with a significant proportion of cases being labeled as idiopathic. Genetic pancreatitis (GP) is associated with mutations of cystic fibrosis transmembrane conductor regulator gene (CFTR), cationic trypsinogen (PRSS1) gene, and serine protease inhibitor Kazal type 1 (SPINK1). There literature is sparse regarding the clinical profile of GP in children. The aim of the present study was to estimate the prevalence and describe the clinical characteristics and outcome of genetic pancreatitis.

METHODS

We reviewed the charts of children ages 18 years or younger with RAP or CP diagnosed from 2000 to 2009 at the Children's Hospital of Wisconsin, Milwaukee. Twenty-nine patients with RAP or CP were identified, of whom 23 (79%) were positive for mutations in ≥1 of the above-mentioned genes, and were included for review.

RESULTS

The median age of symptom onset was 5 years (range 9 months-15 years) with diagnosis at 6.5 years (range 1-16 years). Twenty-one were white; 14 were girls. The most common presenting symptoms were abdominal pain and vomiting. Patients with RAP had 2 to 8 episodes of pancreatitis during 3.6-year average follow-up. Family history was positive in 5 of 29 of gene-tested patients. CFTR, SPINK1, or PRSS1 mutations were seen in 14 (48%), 8 (27%), and 7 (24%) patients, respectively. Two patients were homozygous for CFTR mutations, 6 heterozygote and 4 patients had 5 T variants. Two other patients had double heterozygous mutations in F508 del/2789 + 5G > A and F508 del/5T variant. Six patients with CP had a combination of CFTR and SPINK1 or PRSS1 mutations. Eleven of 29 (38%) patients met radiological criteria for CP. All of the heterozygote patients with a combination of CFTR and SPINK1 or PRSS1 mutations had CP. Eight patients developed a chronic pain syndrome and 2 developed exocrine pancreatic insufficiency during follow-up.

CONCLUSIONS

We found a high prevalence of genetic mutations in patients without anatomic or metabolic abnormalities known to be associated with pancreatitis. Studies are needed to ascertain the genetic causes of RAP and CP and examine the relation between single CFTR mutations and single mutations in the PRSS1 and SPINK1 genes.

[Genetically determined pancreatic diseases]

Overall, genetically determined diseases of the pancreas are rare. Recently, it was demonstrated that in chronic pancreatitis many patients carry genetic changes in associated genes. Aside from chronic pancreatitis, cystic fibrosis is also characterized by exocrine insufficiency in many patients. Genetic alterations in CFTR can be found in patients suffering from chronic pancreatitis and in patients with cystic fibrosis. According to this fact, the analysis of CFTR alterations in both disease forms has improved the understanding of underlying pathogenetic mechanisms. Shwachman-Diamond and Johanson Blizzard syndrome are rare pancreatic disorders, characterized by exocrine pancreatic insufficiency in addition to other phenotypic features. As such, due to the early onset of both disease forms, diagnosis of cystic fibrosis has to be ruled out in patients with exocrine insufficiency, which can be achieved by performing sweat chloride tests. Even pancreatic cancer can accumulate in some families and a genetic basis was recently demonstrated for some patients. In all mentioned disease entities, a genetic analysis of associated genes has become essential for establishing the diagnosis. Although genetic knowledge and the finding of genetic alterations in different genes has not changed therapy of the mentioned diseases so far, the future will tell in which way genetic knowledge can be integrated to change modalities of therapy.

Pancreas divisum does not cause pancreatitis, but associates with CFTR mutations

Bertin et al. partially dispel arguments that pancreas divisum (PD) causes pancreatitis, but fascinatingly indicate that PD associates with CFTR gene mutations predisposing to pancreatitis. This association, however, does not definitely confer a pathophysiological role for PD in pancreatitis but may denote that PD co-mingles with CFTR mutations without influencing pancreatitis or CFTR mutations influence pancreatic duct embryogenesis. We advise "idiopathic pancreatitis" patients with PD to undergo genetic testing. In lieu of CFTR mutations undertake no endoscopic/surgical procedure; if CFTR mutations are found, then refer patients for genetic counseling and withhold endoscopic/surgical therapy unless randomized studies show benefit.

Recommendations for the classification of diseases as CFTR-related disorders

Several diseases have been clinically or genetically related to cystic fibrosis (CF), but a consensus definition is lacking. Here, we present a proposal for consensus guidelines on cystic fibrosis transmembrane conductance regulator (CFTR)-related disorders (CFTR-RDs), reached after expert discussion and two dedicated workshops. A CFTR-RD may be defined as "a clinical entity associated with CFTR dysfunction that does not fulfil diagnostic criteria for CF". The utility of sweat testing, mutation analysis, nasal potential difference, and/or intestinal current measurement for the differential diagnosis of CF and CFTR-RD is discussed. Algorithms which use genetic and functional diagnostic tests to distinguish CF and CFTR-RDs are presented. According to present knowledge, congenital bilateral absence of vas deferens (CBAVD), acute recurrent or chronic pancreatitis and disseminated bronchiectasis, all with CFTR dysfunction, are CFTR-RDs.

[Pancreatitis in cystic fibrosis: association with genotype and pancreatic status]

INTRODUCTION

Pancreatitis is an uncommon complication of cystic fibrosis (CF). Either single or recurrent acute episodes can occur and it occasionally may follow a protracted course with relentless destruction of the pancreas. Moreover mild mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) have been found in many cases of idiopathic chronic pancreatitis. We describe a group of patients with CF who had one or more episodes of pancreatitis. We have estimated its prevalence in a large population of patients with CF across Spain.

METHODS

A retrospective descriptive study was conducted by collecting the demographic, clinical and laboratory data, pancreatic status and genotype of CF patients who attended the CF Units in 5 Spanish hospitals.

RESULTS

The overall number of CF patients under follow-up in the five centres was 520, of which 17 cases with pancreatitis were identified. The prevalence of pancreatitis in this population was 3.3%, higher than previously reported. Noticeably eight of the 17 patients (47.06%) had pancreatic insufficiency. This appears to be, partly, in contrast with that classically found, as this complication is usually associated with patients with a certain level of pancreatic reserve. No associations with genotype, age, gender or other factors were found.

CONCLUSIONS

The prevalence of pancreatitis in our CF patients was higher than that found in other CF populations, and was not limited to patients with pancreatic sufficiency. It occurred mostly in teenagers and young adults often with mild pulmonary disease. The CF genotype was variable. The course of the patients should be carefully monitored, and further information on the long-term outcome of larger cohorts of patients is needed.

A novel exon duplication of the cystic fibrosis transmembrane conductance regulator in a patient presenting with adult-onset recurrent pancreatitis

Pancreatitis is a rare occurrence in patients with cystic fibrosis (CF) affecting 1.2% of all patients, but it can be the first presenting sign in approximately 15% of adults with pancreatic sufficiency and a milder CF phenotype. We report a case of a woman with recurrent pancreatitis who has one cystic fibrosis-causing mutation (G551D) and the first known description of a pathologic duplication of exon 19 of the CF transmembrane conductance regulator (CFTR). A 30-year-old white woman with 30 attacks of pancreatitis over a 5-year period starting at age 25 presented to the genetics department. She was found to have a mutation in the SPINK1 gene, IVS3+184T>A, and one cystic fibrosis-causing mutation (G551D) prompting full gene sequencing of the CFTR, revealing an additional duplication of exon 19. Sweat chloride testing was elevated at 97 and 106 mmol/L. Despite normal growth parameters and lung function, it is important to be aware of recurrent pancreatitis as a presenting sign of CF. Comprehensive CF gene analysis is necessary to detect a second CF-causing mutation that may put patients at risk for more severe symptoms of pancreatitis. There is a significant difference in the prevalence of heterozygote mutations between available testing methods.

Pancreas divisum

We review important new clinical observations in pancreas divisum (PD) made since 2007. PD is common and has the same prevalence in the general population and idiopathic pancreatitis (IP). Up to 53% of patients with PD and IP have underlying idiopathic chronic pancreatitis (CP), and in rigorous prospective clinical follow-up and/or natural history studies, many with idiopathic recurrent acute pancreatitis (IRAP) have idiopathic CP. According to retrospective studies, PD does not modify the natural course of nonalcoholic or alcoholic CP. CFTR and/or SPINK1 gene mutations associate with IP (idiopathic CP and IRAP) independently of the presence of PD. More than one third of patients with pancreatitis or presumed pancreaticobiliary pain respond to placebo. Authors of uncontrolled studies report a significant symptomatic response to surgery and endotherapy in patients with IP and PD, but the response remains unproven and is largely limited to those with IRAP and not idiopathic CP or chronic pain.

The etiology of acute recurrent pancreatitis in children: a challenge for pediatricians

OBJECTIVES

To assess specific etiologies of acute recurrent pancreatitis at a single Italian pediatric cystic fibrosis (CF) center.

METHODS

We studied, retrospectively, 78 young patients (39 female subjects; mean age at diagnosis, 8.8 ± 5.1 years) affected by acute recurrent episodes of pancreatitis, remained etiologically undiagnosed at first-level assessment. All patients were submitted to endoscopic retrograde cholangiopancreatography to exclude biliopancreatic malformations and tested for CF by a sweat chloride test. Most patients also were studied for the research of CFTR, PRSS1, and SPINK1 gene mutations.

RESULTS

A high percentage of family history for chronic pancreatitis was observed (20.5%). The sweat test identified 8 subjects (10.3%) with classic CF (2 patients) or at risk for CF (6 patients). Genetic analysis showed mutations in CFTR, SPINK1, and PRSS1 genes in 39.6%, 7.1%, and 4.5% of patients, respectively. A biliopancreatic malformation was diagnosed in 15 patients (19.2%). We also observed biliary lithiasis (5 patients [6.5%]), congenital pancreatic polycystosis (2 patients), a case of dyslipidemia, and 1 patient with a posttransplantation, drug-induced pancreatitis.

CONCLUSIONS

Recurrent pancreatitis in children has several etiologies. Genetic testing confirms the high frequency of CFTR mutations. This suggests that it is of some value to identify patients with late-onset CF and CFTR-related disorders.

Type of CFTR mutation determines risk of pancreatitis in patients with cystic fibrosis

BACKGROUND & AIMS

Different mutations in the cystic fibrosis gene (CFTR) are associated with different functional status of the exocrine pancreas. We investigated whether CFTR genotypes determine the risk of pancreatitis in patients with cystic fibrosis (CF).

METHODS

Patients with pancreatic-sufficient CF were identified from 2 CF population-based databases (N = 277; 62 with pancreatitis and 215 without pancreatitis); patients' genotypes and clinical characteristics were analyzed. The loss of pancreatic function associated with each CFTR genotype was determined based on the pancreatic insufficiency prevalence (PIP) score.

RESULTS

Patients with pancreatitis were more likely to have genotypes associated with mild (70%) than moderate-severe (30%) PIP scores (P = .004). The cumulative proportion of patients who developed pancreatitis through to the age of 50 years was significantly greater for genotypes associated with mild (50%) than moderate-severe (27%) PIP scores (P = .006). The genotype associated with mild PIP scores had a hazard ratio of 2.4 for pancreatitis (95% confidence interval, 1.3-4.5; P = .006). Patients with pancreatitis were diagnosed with CF at an older median age than those without pancreatitis (14.9 years [interquartile range, 9.5-27.7] vs 9.3 years [interquartile range, 1.5-21.4]; P = .003) and had lower mean levels of sweat chloride than patients without pancreatitis (74.5 ± 26.2 mmol/L vs 82.8 ± 25.2 mmol/L; P = .03).

CONCLUSIONS

Specific CFTR genotypes are significantly associated with pancreatitis. Patients with genotypes associated with mild phenotypic effects have a greater risk of developing pancreatitis than patients with genotypes associated with moderate-severe phenotypes. This observation provides further insight into the complex pathogenesis of pancreatitis.

CFTR gene mutation in patients with apparently idiopathic pancreatitis: lack of phenotype-genotype correlation

BACKGROUND AND AIMS

Despite an extensive search, no cause is found for recurrent acute/chronic pancreatitis (idiopathic pancreatitis (IP)) in about 20% of patients. In these patients, CFTR gene mutations may be identified. The aims of this study were (1) to describe the natural history of pancreatitis associated with the CFTR mutation, (2) to look for genotype-phenotype correlations, and (3) to examine the frequency of CFTR mutations in a population of patients with IP.

RESULTS

100 consecutive patients with IP were included between 1998 and 2005. 50% had one of the 33 most frequent CFTR gene mutations (common CF mutations, uncommon mutations causing variable phenotypes and variants of unknown significance in 28, 44 and 28%, respectively). Patients with a CFTR gene mutation were significantly younger than those without (34 vs. 40 years, p = 0.03). Duration of follow-up (3.5 vs. 3 years), proportion of patients with acute pancreatitis as first symptom (76 vs. 74%) were not significantly different. Signs of chronic pancreatitis (ductal changes and pancreatic calcifications), pseudocysts, common bile duct stenosis, exocrine or endocrine insufficiency occurred in 36, 26, 4, 10 and 12% of patients with CFTR gene mutations respectively, which was not different from patients without mutations. No phenotype-genotype correlation was observed.

CONCLUSIONS

In patients with IP, clinical and radiological manifestations are not related to the presence of a CFTR gene mutation or to the type of mutation.

Cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations and risk for pancreatic adenocarcinoma

BACKGROUND

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene are common in white persons and are associated with pancreatic disease. The purpose of this case-control study was to determine whether CFTR mutations confer a higher risk of pancreatic cancer.

METHODS

In a case-control study, the authors compared the rates of 39 common cystic fibrosis-associated CFTR mutations between 949 white patients with pancreatic adenocarcinoma and 13,340 white controls from a clinical laboratory database for prenatal testing for CFTR mutations. The main outcome measure was the CFTR mutation frequency in patients and controls.

RESULTS

Overall, 50 (5.3%) of 949 patients with pancreatic cancer carried a common CFTR mutation versus 510 (3.8%) of 13,340 controls (odds ratio [OR], 1.40; 95% confidence interval [CI], 1.04-1.89; P = .027). Among patients who were younger when their disease was diagnosed (<60 years), the carrier frequency was higher than in controls (OR, 1.82; 95% CI, 1.14-2.94; P = .011). In patient-only analyses, the presence of a mutation was associated with younger age (median 62 vs 67 years; P = .034). In subgroups, the difference was seen only among ever-smokers (60 vs 65 years, P = .028). Subsequent sequencing analysis of the CFTR gene detected 8 (16%) compound heterozygotes among the 50 patients initially detected to have 1 mutation.

CONCLUSIONS

Carrying a disease-associated mutation in CFTR is associated with a modest increase in risk for pancreatic cancer. Those affected appear to be diagnosed at a younger age, especially among smokers. Clinical evidence of antecedent pancreatitis was uncommon among both carriers and noncarriers of CFTR mutations.