Independent contribution of common CFTR variants to chronic pancreatitis

Germline multigene panel testing in acute and chronic pancreatitis

BACKGROUND/OBJECTIVES

Germline genetic testing is recommended for younger patients with idiopathic pancreatitis but there has been a lack of consensus in recommendations for those over age 35. We aimed to analyze the results of genetic testing among subjects of varying ages.

METHODS

Individuals who underwent germline multigene testing for pancreatitis susceptibility genes (CASR, CFTR, CPA1, CTRC, PRSS1, SPINK1) through a large commercial laboratory between 2017 and 2022 were included. Test results and information collected from test requisition forms were evaluated. Multivariable logistic regression models were performed to identify factors associated with a positive pancreatitis panel (pathogenic, likely pathogenic, and/or increased risk variants) in pancreatitis-related genes.

RESULTS

Overall, 2,468 subjects with primary indication of acute pancreatitis (AP) (n = 401), chronic pancreatitis (CP) (n = 631), pancreatic cancer (n = 128), or other indications (n = 1,308) completed germline testing. Among patients with AP or CP, the prevalence of any positive result for those <35 versus ≥35 years of age was 32.1% and 24.5% (p = 0.007), and the prevalence of a clinically meaningful result was 10.8% and 5.4%, respectively (p = 0.001). Positive family history of pancreatitis was associated with increased odds ratio (OR) of 8.59 (95% confidence interval (CI) 2.92-25.25) for a clinically significant panel result while each 5-year increase in age at test completion had lower odds (OR 0.89, 95% CI 0.83-0.95).

CONCLUSIONS

The highest prevalence of pathogenic variants is seen in younger individuals with a positive family history of pancreatitis. However, clinically meaningful results are identified in older subjects, suggesting that genetic counseling and testing should be considered for all age groups.

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.

Positive epistasis between disease-causing missense mutations and silent polymorphism with effect on mRNA translation velocity

Epistasis refers to the dependence of a mutation on other mutation(s) and the genetic context in general. In the context of human disorders, epistasis complicates the spectrum of disease symptoms and has been proposed as a major contributor to variations in disease outcome. The nonadditive relationship between mutations and the lack of complete understanding of the underlying physiological effects limit our ability to predict phenotypic outcome. Here, we report positive epistasis between intragenic mutations in the cystic fibrosis transmembrane conductance regulator (CFTR)-the gene responsible for cystic fibrosis (CF) pathology. We identified a synonymous single-nucleotide polymorphism (sSNP) that is invariant for the CFTR amino acid sequence but inverts translation speed at the affected codon. This sSNP in cis exhibits positive epistatic effects on some CF disease-causing missense mutations. Individually, both mutations alter CFTR structure and function, yet when combined, they lead to enhanced protein expression and activity. The most robust effect was observed when the sSNP was present in combination with missense mutations that, along with the primary amino acid change, also alter the speed of translation at the affected codon. Functional studies revealed that synergistic alteration in ribosomal velocity is the underlying mechanism; alteration of translation speed likely increases the time window for establishing crucial domain-domain interactions that are otherwise perturbed by each individual mutation.

Carriers of cystic fibrosis among sperm donors: complete CFTR gene analysis versus CFTR genotyping

OBJECTIVE

To determine the frequency of cystic fibrosis (CF) carriers among sperm donors in Spain studied through a complete analysis of the CFTR gene and to compare the results with those that would have been obtained by the 4 genotyping panels of the CFTR gene most commonly used as a carrier test in the context of assisted reproduction in our country.

DESIGN

Descriptive observational study.

SETTING

Private center.

PATIENTS

Nine hundred thirty-five sperm donors, from January 2014 to June 2019.

INTERVENTION

None.

MAIN OUTCOME MEASURE

Presence of pathogenic variants in the CFTR gene.

RESULTS

17% of the donors were carriers of at least 1 pathogenic variant in CFTR, with 39 different pathogenic variants detected. Only 4 of these 39 variants (10.27%) would have been detected by the 4 genotyping tests considered, and 22 variants (56.41%) would not have been detected by any of the genotyping tests. The pathogenic variants of the CFTR gene included in the different genotyping tests analyzed vary widely, and <50% are common to all of them.

CONCLUSIONS

Although the was not based in the general population, these results show that the use of genotyping tests is associated with a high reproductive risk, because the rate of detection of CF carriers was lower when these panels were applied, in comparison with the complete study of the CFTR gene. We recommend that complete sequencing of the CFTR gene by next-generation sequencing be performed as a screening method for CF in sperm donors.

Cystic fibrosis gene mutations and polymorphisms in Saudi men with infertility

BACKGROUND

Some mutations of the cystic fibrosis transmembrane regulator (CFTR) gene may impair spermatogenesis or cause a congenital absence of the vas deferens that manifests as isolated male infertility.

OBJECTIVE

Assess the frequency and analyze the spectrum of CFTR gene variations in Saudi men with primary infertility.

DESIGN

Prospective, cross-sectional.

SETTING

Tertiary care specialist hospital in Jeddah.

PATIENTS AND METHODS

Genomic DNA was extracted from peripheral blood samples of Saudi men who presented with primary infertility to the outpatient andrology clinic with either azoospermia or oligoasthenoteratozoospermia. Polymerase chain reaction and direct sequencing were used to identify all variants of the CFTR gene.

MAIN OUTCOME MEASURES

Proportion of the patients with a mutant CFTR gene and the spectrum of CFTR gene variations.

SAMPLE SIZE

50 infertile Saudi men.

RESULTS

This study identified 10 CFTR gene variants in 7 (14%) subjects (100 chromosomes). The detected variants and polymorphisms were: c.1408G>A, c.4389G>A, c.2562T>G, c.869+11C>T, c.2909-92G>A, c.3469-65C>A, c.1210-6delT, c.1210-6T>A, c.2988+1G>A, and c.1210-13GT>TG.

CONCLUSION

We demonstrated that 14% of the study subjects had one or more CFTR mutations and these were compounded in most of the affected patients. The spectrum of CFTR gene mutations in these subjects was similar to the mutations reported in other studies throughout the world.

LIMITATIONS

Small sample size and the lack of a control group.

CONFLICTS OF INTEREST

None.

The Cystic Fibrosis Transmembrane Conductance Regulator 470 Met Allele Is Associated with an Increased Risk of Chronic Pancreatitis in Both Asian and Caucasian Populations: A Meta-Analysis

Background: The Met470Val polymorphism (1540A>G [rs213950]) within the cystic fibrosis transmembrane conductance regulator (CFTR) protein has been reported to be associated with chronic pancreatitis (CP). The results remain inconclusive, and therefore, we performed this meta-analysis to clarify the association between M470V and CP risk. Methodology/Results: We conducted a meta-analysis of 7 case-control studies, including a total of 1121 CP patients and 2209 controls from Asian and Caucasian populations. We calculated the odds ratio (OR) and 95% confidence intervals (95% CI). Met470Val was found to be significantly associated with an increased risk of CP under all the genetic models (M vs. V, OR = 1.260, 95% CI: 1.134-1.399; MV vs. VV, OR = 1.292, 95% CI: 1.091-1.530; MM vs. VV, OR = 1.579, 95% CI: 1.274-1.956; MV/MV vs. VV, OR = 1.366, 95% CI: 1.165-1.603; MM vs. MV/VV, OR = 1.346, 95% CI: 1.114-1.621). Met470Val was also found to be significantly associated with an increased risk of idiopathic CP (ICP) in allele contrast, codominant, and recessive models (M vs. V, OR = 1.298, 95% CI: 1.020-1.653; MV vs. VV, OR = 1.297, 95% CI: 1.074-1.566; MM vs. VV, OR = 1.473, 95% CI: 1.165-1.862; MM vs. MV/VV, OR = 1.254, 95% CI: 1.023-1.538). Conclusions: The CFTR 470 M allele is significantly associated with an increased risk of CP in both Asian and Caucasian populations. The CFTR 470 M allele is also significantly associated with risk of ICP.

IVS8-5T Allele of CFTR is the Risk Factor in Chronic Pancreatitis, Especially in Idiopathic Chronic Pancreatitis

BACKGROUND

Cystic fibrosis transmembrane conductance regulator IVS8-5T gene variation appears to be associated with a higher risk of chronic pancreatitis (CP); however, there is inconsistency between previous reported studies. Here, we performed a meta-analysis to investigate this relationship.

MATERIALS AND METHODS

PubMed and WANFANG databases were searched for the case-control studies that contained Patients with CP with IVS8-5T variation. Odd ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the relevance of IVS8-5T gene variation and CP.

RESULTS

Analysis showed that the frequency of the 5T allele was significantly higher in CP subjects than that in control subjects (OR = 1.43, 95% CI: 1.13-1.81, I² = 1.2%). Based on the subgroup analysis stratified by etiology, the 5T allele was associated with a higher risk of idiopathic chronic pancreatitis (ICP) (OR = 1.80, 95% CI: 1.18-2.76, I² = 0.0%) and not alcoholic CP (OR = 2.14, 95% CI: 0.98-4.66, I² = 0.0%). Further study indicated that the 5T allele was related to higher ICP prevalence in the European population (OR = 1.79, 95% CI: 1.06-3.03, I² = 0.0%). In contrast, there was no significant difference between ICP subjects and healthy controls within the Asian population (OR = 1.84, 95% CI: 0.91-3.72, I² = 38.0%).

CONCLUSIONS

Cystic fibrosis transmembrane conductance regulator IVS8-5T is a risk factor in patients with CP. IVS8-5T variation may play a significant role in the occurrence of ICP, especially in the European population.

Synchronous Periampullary Tumors in a Patient With Pancreas Divisum and Neurofibromatosis Type 1

INTRODUCTION

In this study, we describe for the first time a Neurofibromatosis type 1 patient with pancreas divisum, multiple periampullary tumors and germline pathogenic variants in NF1 and CFTR genes.

CASE REPORT

A 62-year-old female NF1 patient presented with weakness, choluria, nausea, and diffuse abdominal pain to an emergency room service. Magnetic resonance imaging revealed an abdominal mass involving the periampullary region and pancreas divisum. After surgical resection, three synchronous neoplasms were detected including two ampullary tumors (adenocarcinoma of the major ampulla and a neuroendocrine tumor of the minor ampulla) and a gastrointestinal stromal tumor (GIST). Germline multigene panel testing (MGPT) identified two pathogenic heterozygous germline variants: NF1 c.838del and CFTR c.1210-34TG[12]T[5].

CONCLUSION

This is the first report of a Neurofibromatosis type 1 patient with pancreas divisum and multiple periampullary tumors harboring pathogenic germline variants in NF1 and CFTR genes. The identification of two germline variants and a developmental anomaly in this patient may explain the unusual and more severe findings and underscores the importance of comprehensive molecular analyses in patients with complex phenotypes.

Timing during translation matters: synonymous mutations in human pathologies influence protein folding and function

Ribosomes translate mRNAs with non-uniform speed. Translation velocity patterns are a conserved feature of mRNA and have evolved to fine-tune protein folding, expression and function. Synonymous single-nucleotide polymorphisms (sSNPs) that alter programmed translational speed affect expression and function of the encoded protein. Synergistic advances in next-generation sequencing have led to the identification of sSNPs associated with disease penetrance. Here, we draw on studies with disease-related proteins to enhance our understanding of mechanistic contributions of sSNPs to functional alterations of the encoded protein. We emphasize the importance of identification of sSNPs along with disease-causing mutations to understand genotype-phenotype relationships.

Congenital bilateral absence of the vas deferens as an atypical form of cystic fibrosis: reproductive implications and genetic counseling

Congenital bilateral absence of the vas deferens (CBAVD) is found in 1% to 2% of males with infertility and is present in 6% of obstructive azoospermia cases. Nearly 95% of men with cystic fibrosis (CF, an autosomal recessive disorder) have CBAVD. There are genetic links between CBAVD and CF. Some mutations in the gene encoding cystic fibrosis transmembrane conductance regulator (CFTR) can lead to CBAVD as a monosymptomatic form of CF. With the use of assisted reproductive techniques (ART), especially testicular or epididymal sperm aspiration, intracytoplasmic sperm injection, and in vitro fertilization, it is possible that men with CBAVD can produce offspring. Therefore, genetic counseling should be offered to couples undergoing ART to discuss the probability of having offspring that carry CFTR gene mutations. The aim of this review was to present the main cause of CBAVD, to call attention to its implications for assisted reproduction, and to show the importance of genetic counseling for couples where men have CBAVD, as they can have offspring with a lethal disease.

Association between F508 deletion in CFTR and chronic pancreatitis risk

BACKGROUND

The cystic fibrosis transmembrane conductance regulator (CFTR) has been reported to influence individual susceptibility to chronic pancreatitis (CP), but the results of previous studies are controversial.

AIMS

We performed a study to demonstrate the relationship between CFTR and CP.

METHODS

We searched PubMed, Scopus, and Embase for studies of patients with CP. Seven studies from 1995 to 2016 were identified, and included 64,832 patients. Pooled prevalence and 95% confidence intervals (CIs) were calculated.

RESULTS

F508 deletion in CFTR was significantly positively associated with CP risk in the overall analysis (odds ratio [OR]=3.20, 95% CI: 2.30-4.44, I²=31.7%). In subgroup analysis stratified by ethnicity, F508 deletion was significantly associated with CP risk in Indian populations, using a fixed effects model (ORs=5.45, 95% CI: 2.52-11.79, I²=0.0%), and in non-Indian populations, using a random effects model (ORs=3.59, 95% CI: 1.73-7.48, I²=60.9%). At the same time, we found that Indians with F508 deletion had much higher CP prevalence than non-Indians. Interestingly, F508 deletion was also associated with CP and idiopathic CP risk in subgroup analysis stratified by aeitiology, using the fixed effects model.

CONCLUSIONS

Based on current evidence, F508 deletion is a risk factor for CP, and Indians with F508 deletion have much higher CP morbidity.

Cystic fibrosis transmembrane conductance regulator (CFTR) gene abnormalities in Indian males with congenital bilateral absence of vas deferens & renal anomalies

Background & objectives:

The role of cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations in congenital bilateral absence of vas deferens and unilateral renal agenesis (CBAVD-URA) has been controversial. Here, we report the cases of five Indian males with CBAVD-URA. The objective was to evaluate the presence or absence of CFTR gene mutations and variants in CBAVD-URA. The female partners of these males were also screened for cystic fibrosis (CF) carrier status.

Methods:

Direct DNA sequencing of CFTR gene was carried out in five Indian infertile males having CBAVD-URA. Female partners (n=5) and healthy controls (n=32) were also screened.

Results:

Three potential regulatory CFTR gene variants (c.1540A>G, c.2694T>G and c.4521G>A) were detected along with IVS8-5T mutation in three infertile males with CBAVD-URA. Five novel CFTR gene variants (c.621+91A>G, c.2752+106A>T, c.2751+85_88delTA, c.3120+529InsC and c.4375-69C>T), four potential regulatory CFTR gene variants (M470V, T854T, P1290P, Q1463Q) and seven previously reported CFTR gene variants (c.196+12T>C, c.875+40A>G, c.3041-71G>C, c.3271+42A>T, c.3272-93T>C, c.3500-140A>C and c.3601-65C>A) were detected in infertile men having CBAVD and renal anomalies

Interpretation & conclusions:

Based on our findings, we speculate that CBAVD-URA may also be attributed to CFTR gene mutations and can be considered as CFTR-related disorder (CFTR-RD). The CFTR gene mutation screening may be offered to CBAVD-URA men and their female partners undergoing ICSI. Further studies need to be done in a large sample to confirm the findings.

Alteration of protein function by a silent polymorphism linked to tRNA abundance

Synonymous single nucleotide polymorphisms (sSNPs) are considered neutral for protein function, as by definition they exchange only codons, not amino acids. We identified an sSNP that modifies the local translation speed of the cystic fibrosis transmembrane conductance regulator (CFTR), leading to detrimental changes to protein stability and function. This sSNP introduces a codon pairing to a low-abundance tRNA that is particularly rare in human bronchial epithelia, but not in other human tissues, suggesting tissue-specific effects of this sSNP. Up-regulation of the tRNA cognate to the mutated codon counteracts the effects of the sSNP and rescues protein conformation and function. Our results highlight the wide-ranging impact of sSNPs, which invert the programmed local speed of mRNA translation and provide direct evidence for the central role of cellular tRNA levels in mediating the actions of sSNPs in a tissue-specific manner.

Synonymous single nucleotide polymorphisms (sSNPs) occur at high frequency in the human genome and are associated with ~50 diseases in humans; the responsible molecular mechanisms remain enigmatic. Here, we investigate the impact of the common sSNP, T2562G, on cystic fibrosis transmembrane conductance regulator (CFTR). Although this sSNP, by itself, does not cause cystic fibrosis (CF), it is prevalent in patients with CFTR-related disorders. T2562G sSNP modifies the local translation speed at the Thr854 codon, leading to changes in CFTR stability and channel function. This sSNP introduces a codon pairing to a low-abundance tRNA, which is particularly rare in human bronchial epithelia, but not in other human tissues, suggesting a tissue-specific effect of this sSNP. Enhancement of the cellular concentration of the tRNA cognate to the mutant ACG codon rescues the stability and conduction defects of T2562G-CFTR. These findings reveal an unanticipated mechanism—inverting the programmed local speed of mRNA translation in a tRNA-dependent manner—for sSNP-associated diseases.

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.

Mechanisms of CFTR functional variants that impair regulated bicarbonate permeation and increase risk for pancreatitis but not for cystic fibrosis

CFTR is a dynamically regulated anion channel. Intracellular WNK1-SPAK activation causes CFTR to change permeability and conductance characteristics from a chloride-preferring to bicarbonate-preferring channel through unknown mechanisms. Two severe CFTR mutations (CFTRsev) cause complete loss of CFTR function and result in cystic fibrosis (CF), a severe genetic disorder affecting sweat glands, nasal sinuses, lungs, pancreas, liver, intestines, and male reproductive system. We hypothesize that those CFTR mutations that disrupt the WNK1-SPAK activation mechanisms cause a selective, bicarbonate defect in channel function (CFTRBD) affecting organs that utilize CFTR for bicarbonate secretion (e.g. the pancreas, nasal sinus, vas deferens) but do not cause typical CF. To understand the structural and functional requirements of the CFTR bicarbonate-preferring channel, we (a) screened 984 well-phenotyped pancreatitis cases for candidate CFTRBD mutations from among 81 previously described CFTR variants; (b) conducted electrophysiology studies on clones of variants found in pancreatitis but not CF; (c) computationally constructed a new, complete structural model of CFTR for molecular dynamics simulation of wild-type and mutant variants; and (d) tested the newly defined CFTRBD variants for disease in non-pancreas organs utilizing CFTR for bicarbonate secretion. Nine variants (CFTR R74Q, R75Q, R117H, R170H, L967S, L997F, D1152H, S1235R, and D1270N) not associated with typical CF were associated with pancreatitis (OR 1.5, p = 0.002). Clones expressed in HEK 293T cells had normal chloride but not bicarbonate permeability and conductance with WNK1-SPAK activation. Molecular dynamics simulations suggest physical restriction of the CFTR channel and altered dynamic channel regulation. Comparing pancreatitis patients and controls, CFTRBD increased risk for rhinosinusitis (OR 2.3, p<0.005) and male infertility (OR 395, p<<0.0001). WNK1-SPAK pathway-activated increases in CFTR bicarbonate permeability are altered by CFTRBD variants through multiple mechanisms. CFTRBD variants are associated with clinically significant disorders of the pancreas, sinuses, and male reproductive system.

Genetic risk factors for pancreatic disorders

A combination of genetic, environmental, and metabolic factors contribute to the development and recurrence of acute and chronic pancreatitis; information on all of these is required to manage patients effectively. For example, variants that affect regulation of the protease, serine (PRSS)1-PRSS2, and claudin (CLDN)2 loci, rather than their coding sequences, interact with other genetic and environmental factors to affect disease development. New strategies are needed to use these data and determine their contribution to pathogenesis, because these variants differ from previously studied, rare variants in exons (coding regions) of genes such as PRSS1, SPINK1, cystic fibrosis transmembrane conductance regulator (CFTR), chymotrypsin (CTR)C, and calcium-sensing receptor (CASR). Learning how various genetic factors affect pancreatic cells and systems could lead to etiology-based therapies rather than treatment of symptoms.

The Spanish Pancreatic Club recommendations for the diagnosis and treatment of chronic pancreatitis: part 1 (diagnosis)

Chronic pancreatitis (CP) is a relatively uncommon, complex and heterogeneous disease. The absence of a gold standard applicable to the initial phases of CP makes its early diagnosis difficult. Some of its complications, particularly chronic pain, can be difficult to manage. There is much variability in the diagnosis and treatment of CP and its complications amongst centers and professionals. The Spanish Pancreatic Club has developed a consensus on the management of CP. Two coordinators chose a multidisciplinary panel of 24 experts on this disease. A list of questions was drafted, and two experts reviewed each question. Then, a draft was produced and shared with the entire panel of experts and discussed in a face-to-face meeting. This first part of the consensus addresses the diagnosis of CP and its complications.

Genetic variation and clinical heterogeneity in cystic fibrosis

Cystic fibrosis (CF), a lethal genetic disease, is characterized by substantial clinical heterogeneity. Work over the past decade has established that much of the variation is genetically conferred, and recent studies have begun to identify chromosomal locations that identify specific genes as contributing to this variation. Transcriptomic and proteomic data, sampling hundreds and thousands of genes and their products, point to pathways that are altered in the cells and tissues of CF patients. Genetic studies have examined more than half a million polymorphic sites and have identified regions, and probably genes, that contribute to the clinical heterogeneity. The combination of these approaches has great potential because genetic profiling identifies putative disease-modifying processes, and transcript and protein profiling is shedding light on the biology involved. Such studies are providing new insights into the disease, such as altered apoptotic responses, oxidative stress dysregulation, and neuronal involvement, all of which may open new therapeutic avenues to exploration.

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.