Pancreatitis severity in mice with impaired CFTR function but pancreatic sufficiency is mediated via ductal and inflammatory cells-Not acinar cells

Mutations in the cystic fibrosis transmembrane conductance regulator gene (CFTR) are an established risk factor for cystic fibrosis (CF) and chronic pancreatitis. Whereas patients with CF usually develop complete exocrine pancreatic insufficiency, pancreatitis patients with CFTR mutations have mostly preserved exocrine pancreatic function. We therefore used a strain of transgenic mice with significant residual CFTR function (CFTR^tm1HGU) to induce pancreatitis experimentally by serial caerulein injections. Protease activation and necrosis were investigated in isolated acini, disease severity over 24h, pancreatic function by MRI, isolated duct stimulation and faecal chymotrypsin, and leucocyte function by ex vivo lipopolysaccharide (LPS) stimulation. Pancreatic and lung injury were more severe in CFTR^tm1HGU but intrapancreatic trypsin and serum enzyme activities higher than in wild-type controls only at 8h, a time interval previously attributed to leucocyte infiltration. CCK-induced trypsin activation and necrosis in acini from CFTR^tm1HGU did not differ from controls. Fluid and bicarbonate secretion were greatly impaired, whereas faecal chymotrypsin remained unchanged. LPS stimulation of splenocytes from CFTR^tm1HGU resulted in increased INF-γ and IL-6, but decreased IL-10 secretion. CFTR mutations that preserve residual pancreatic function significantly increase the severity of experimental pancreatitis—mostly via impairing duct cell function and a shift towards a pro-inflammatory phenotype, not by rendering acinar cells more susceptible to pathological stimuli.     

'CFTR-opathies': disease phenotypes associated with cystic fibrosis transmembrane regulator gene mutations

Cystic fibrosis is a genetic disease that is associated with abnormal sweat electrolytes, sino-pulmonary disease, exocrine pancreatic insufficiency, and male infertility. Insights into genotype/phenotype relations have recently been gained in this disorder. The strongest relationship exists between 'severe' mutations in the gene that encodes the cystic fibrosis transmembrane regulator (CFTR) and pancreatic insufficiency. The relationship between 'mild' mutations, associated with residual CFTR function, and expression of disease is less precise. Atypical 'mild' mutations in the CFTR gene have been linked to late-onset pulmonary disease, congenital bilateral absence of the vas deferens, and idiopathic pancreatitis. Less commonly, sinusitis, allergic bronchopulmonary aspergillosis, and possibly even asthma may also be associated with mutations in the CFTR gene, but those syndromes predominantly reflect non-CFTR gene modifiers and environmental influences.     

Growth induction in cystic fibrosis fibroblasts with low dexamethasone concentrations. Experience with application to genotyping

Summary Dexamethasone (DM) resistance was evaluated in fibroblasts from a pool of five patients with cystic fibrosis (CF) homozygotes, ten of their parental obligate heterozygotes, and seventeen age-matched controls of both sexes. The CF heterozygotes showed a mean DM resistance greater than homozygotes and both groups exhibited a higher mean DM resistance at every DM concentration than controls. However, substantial interassay variability rendered these differences in the total pooled data to non-significance. One control showed a consistently increased resistance and was possibly a covert heterozygote. It was concluded that the phenomenon of DM resistance was exhibited by CF heterozygotes and homozygotes but was not discrete enough for genotyping in the prenatal diagnosis of CF.     

Rapid Detection of the ACMG/ACOG-Recommended 23 CFTR Disease-Causing Mutations Using Ion Torrent Semiconductor Sequencing

Cystic fibrosis (CF) is one of the most frequently diagnosed autosomal-recessive diseases in the Caucasian population. For general-population CF carrier screening, the American College of Medical Genetics (ACMG)/American College of Obstetricians and Gynecologists (ACOG) have recommended a core panel of 23 mutations that will identify 49–98% of carriers, depending on ethnic background. Using a genotyping technology that can rapidly identify disease-causing mutations is important for high-throughput general-population carrier screening, confirming clinical diagnosis, determining treatment options, and prenatal diagnosis. Here, we describe a proof-of-concept study to determine whether the Ion Torrent Personal Genome Machine (PGM) sequencer platform can reliably identify all ACMG/ACOG 23 CF transmembrane conductance regulator (CFTR) mutations. A WT CF specimen along with mutant DNA specimens representing all 23 CFTR mutations were sequenced bidirectionally on the Ion Torrent 314 chip to determine the accuracy of the PGM for CFTR variant detection. We were able to reliably identify all of the targeted mutations except for 2184delA, which lies in a difficult, 7-mer homopolymer tract. Based on our study, we believe PGM sequencing may be a suitable technology for identifying CFTR mutations in the future. However, as a result of the elevated rate of base-calling errors within homopolymer stretches, mutations within such regions currently need to be evaluated carefully using an alternative method.     

The TNFα receptor TNFRSF1A and genes encoding the amiloride-sensitive sodium channel ENaC as modulators in cystic fibrosis

The CFTR mutations in cystic fibrosis (CF) lead to ion transport anomalities which predispose to chronic infection and inflammation of CF airways as the major determinants for morbidity and mortality in CF. Discordant clinical phenotypes of siblings with identical CFTR mutations and the large variability of clinical manifestations of patients who are homozygous for the most common mutation F508del suggest that both environment and genes other than CFTR contribute substantially to CF disease. The prime candidates for genetic modifiers in CF are elements of host defence such as the TNFα receptor and of ion transport such as the amiloride-sensitive epithelial sodium channel ENaC, both of which are encoded side by side on 12p13 (TNFRSF1A, SCNN1A) and 16p12 (SCNN1B, SCNN1G). Thirty-seven families with F508del-CFTR homozygous siblings exhibiting extreme clinical phenotypes that had been selected from the 467 pairs of the European CF Twin and Sibling Study were genotyped at 12p13 and 16p12 markers. The ENaC was identified as a modulator of CF by transmission disequilibrium at SCNN1G and association with CF phenotype intrapair discordance at SCNN1B. Family-based and case-control analyses and sequencing of SCNN1A and TNFRSF1A uncovered an association of the TNFRSF1A intron 1 haplotype with disease severity. Carriers of risk haplotypes were underrepresented suggesting a strong impact of both loci on survival. The finding that TNFRSF1A, SCNN1B and SCNN1G are clinically relevant modulators of CF disease supports current concepts that the depletion of airway surface liquid and inadequate host inflammatory responses trigger pulmonary disease in CF.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

CFTR haplotypic variability for normal and mutant genes in cystic fibrosis families from southern France

In order to contribute to a better understanding of the dispersion of cystic fibrosis (CF) mutations in the South of France, seven diallelic and three multiallelic markers [three upstream of the cystic fibrosis transmembrane conductance regulator (CFTR) gene (XV-2c, KM.19 and J44) and seven intragenic polymorphisms (IVS6A, IVS8CA, M470V, T854T, IVS17BTA, IVS17BCA and TUB18)] were analyzed for 143 ΔF508 chromosomes, 100 CF chromosomes carrying 85 non-ΔF508 and 15 unknown mutations, and 198 normal CFTR alleles. The study provides haplotypic data for 39 different CF mutations, which should be useful in diagnosis by haplotypic analysis and detection of the associated mutations. A major haplotype [2-1-2-7-16-2-1-(30/31)-13-1] was found in normal chromosomes, which should be the most ancient in the Caucasoid population. The most frequent haplotypes in normal chromosomes were associated with 16 different non-ΔF508 mutations, suggesting that there was no preferential haplotype on which these mutations arose. Several mutations were each associated with more than one haplotype, as the result of slippage at one or two of the three microsatellites (ΔF508, G542X, N1303K, G85E, E585X, K710X and 2184delA) or recombination (1717-1G→A, R334W, L206W, R1162X and Y122X). Haplotypes for the most common CFTR mutations (ΔF508, G542X, N1303K) revealed that a large number of alleles were generated by slippage at the microsatellite loci, suggesting that they are the most ancient CF mutations. Other mutations were associated with haplotypes that were different either at several diallelic sites (R334W) or at both diallelic and microsatellite markers (R1162X and R1158X), which is more suggestive of recurrence. Twenty recombinations were detected among the CF mutant alleles analyzed, 75% of them occurring in the second half of the CFTR gene. The higher mutational heterogeneity and the haplotypic variability reported in this small population from the Mediterranean area are consistent with an earlier appearance of CFTR mutations in southern Europe than in central and northern Europe, and an earlier origin and expansion of this population. Received: 19 February 1996 / Revised: 10 April 1996     

Novel and recurrent rearrangements in the CFTR gene: clinical and laboratory implications for cystic fibrosis screening

Because standard techniques used to detect mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene do not detect single or multiple exonic rearrangements, the importance of such rearrangements may be underestimated. Using an in-house developed, single-tube, semi-quantitative fluorescent PCR (SQF PCR) assay, we analyzed 36 DNA samples submitted for extensive CFTR sequencing and identified ten samples with rearrangements. Of 36 patients with classic CF, 10 (28%) harbored various deletions in the CFTR gene, accounting for 14% of CF chromosomes. A deletion encompassing the CFTR promoter and exons 1 and 2 was detected in a sample from one proband, and in the maternal DNA as well. In another family, a deletion of the promoter and exon 1 was detected in three siblings. In both of these cases, the families were African American and the 3120+1G>A splice site mutation was also identified. These promoter deletions have not been previously described. In a third case, a deletion of exons 17a, 17b, and 18 was identified in a Caucasian female and the same mutation was detected in the paternal DNA. In the other seven cases, we identified the following deletions: exons 2 and 3 (n=2); exons 4, 5, and 6a; exons 17a and 17b; exons 22 and 23; and exons 22, 23, and 24 (n=2). In our series, the frequency of CFTR rearrangements in classic CF patients, when only one mutation was identified by extensive DNA sequencing, was >60% (10/16). Screening for exon deletions and duplications in the CFTR gene would be beneficial in classic CF cases, especially when only one mutation is identified by standard methodologies. An erratum to this article can be found at     

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 (CFTR^sev) 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 (CFTR^BD) 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 CFTR^BD 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 CFTR^BD 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, CFTR^BD 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 CFTR^BD variants through multiple mechanisms. CFTR^BD variants are associated with clinically significant disorders of the pancreas, sinuses, and male reproductive system.     

Mukoviszidose – eine pleiotrope Ionenkanalerkrankung mit wesentlicher Lungenbeteiligung

The monogenic disease cystic fibrosis is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene and is inherited in an autosomal recessive fashion. Successful diagnosis of the disease is achieved by patient history, clinical assessment, genetic analysis of the CFTR gene and by in vivo measurement and ex vivo characterization of the basic defect in patient’s samples. Frequently, differential diagnosis of CFTR-related disorders such as congenital bilateral absence of the vas deferens (CBAVD), pancreatitis and bronchiectasis needs to be performed. Molecular therapeutics has been developed for some CFTR mutations and these will facilitate direct clinical use of the information provided by CFTR mutation analysis.     

Cystic-fibrosis-like disease unrelated to the cystic fibrosis transmembrane conductance regulator

Cystic fibrosis (CF) is considered to be a monogenic disease caused by molecular lesions within the cystic fibrosis transmembrane conductance regulator (CFTR) gene and is diagnosed by elevated sweat electrolytes. We have investigated the clinical manifestations of cystic fibrosis, CFTR genetics and electrophysiology in a sibpair in which the brother is being treated as having CF, whereas his sister is asymptomatic. The diagnosis of CF in the index patient is based on highly elevated sweat electrolytes in the presence of CF-related pulmonary symptoms. The investigation of chloride conductance in respiratory and intestinal tissue by nasal potential difference and intestinal current measurements, respectively, provides no evidence for CFTR dysfunction in the siblings who share the same CFTR alleles. No molecular lesion has been identified in the CFTR gene of the brother. Findings in the investigated sibpair point to the existence of a CF-like disease with a positive sweat test without CFTR being affected. Other factors influencing sodium or chloride transport are likely to be the cause of the symptoms in the patient described. Received: 25 August 1997 / Accepted: 20 January 1998     

Susceptibility to typhoid fever is associated with a polymorphism in the cystic fibrosis transmembrane conductance regulator (CFTR)

The cystic fibrosis transmembrane conductance regulator (CFTR) is the affected protein in cystic fibrosis (CF). The high rate of CF carriers has led to speculation that there must be, similar to the sickle cell haemoglobin advantage in malaria, a selective advantage for heterozygotes. Such a selective advantage may be conferred through reduced attachment of Salmonella typhi to intestinal mucosa, thus providing resistance to typhoid fever. We tested this hypothesis by genotyping patients and controls in a typhoid endemic area in Indonesia for two highly polymorphic markers in CFTR and the most common CF mutation. We found an association between genotypes in CFTR and susceptibility to typhoid fever (OR=2.6). These analyses suggest that the role CFTR plays in vitro in S. typhi infection is also important for infection in the human population.Electronic Supplementary Material Supplementary material is available for this article at     

Applications of proteomic technologies for understanding the premature proteolysis of CFTR

Cystic fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene, which encodes an ATP-dependent anion channel. Disease-causing mutations can affect channel biogenesis, trafficking or function, and result in reduced ion transport at the apical surface of many tissues. The most common CFTR mutation is a deletion of phenylalanine at position 508 (ΔF508), which results in a misfolded protein that is prematurely targeted for degradation. This article focuses on how proteomic approaches have been utilized to explore the mechanisms of premature proteolysis in CF. Additionally, we emphasize the potential for proteomic-based technologies in expanding our understanding of CF pathophysiology and therapeutic approaches.     

SNaPshot Assay for the Detection of the Most Common CFTR Mutations in Infertile Men

Congenital bilateral absence of vas deferens (CBAVD) is the most common CFTR-related disorder (CFTR-RD) that explains about 1–2% of the male infertility cases. Controversial data have been published regarding the involvement of CFTR mutations in infertile men with non-obstructive azoospermia and oligozoospermia. Here, we describe single base extension (SNaPshot) assay for detection of 11 common CFTR mutations: F508del, G542X, N1303K, 621+1G->T, G551D, R553X, R1162X, W1282X, R117H, 2184insA and 1717-1G->A and IVS8polyT variants. The assay was validated on 50 previously genotyped samples and was used to screen a total of 369 infertile men with different impairment of spermatogenesis and 136 fertile controls. Our results show that double heterozygosity of cystic fibrosis (CF) and CFTR-related disorder (CFTR-RD) mutations are found in a high percentage (22.7%) of infertile men with obstructive azoospermia, but not in other studied groups of infertile men. The SNaPshot assay described here is an inexpensive, fast and robust method for primary screening of the most common CFTR mutations both in patients with classical CF and CFTR-RD. It can contribute to better understanding of the role of CFTR mutations in impaired spermatogenesis, ultimately leading to improved management of infertile men.     

A Genotypic-Oriented View of CFTR Genetics Highlights Specific Mutational Patterns Underlying Clinical Macrocategories of Cystic Fibrosis

Cystic fibrosis (CF) is a monogenic disease caused by mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The genotype–phenotype relationship in this disease is still unclear, and diagnostic, prognostic and therapeutic challenges persist. We enrolled 610 patients with different forms of CF and studied them from a clinical, biochemical, microbiological and genetic point of view. Overall, there were 125 different mutated alleles (11 with novel mutations and 10 with complex mutations) and 225 genotypes. A strong correlation between mutational patterns at the genotypic level and phenotypic macrocategories emerged. This specificity appears to largely depend on rare and individual mutations, as well as on the varying prevalence of common alleles in different clinical macrocategories. However, 19 genotypes appeared to underlie different clinical forms of the disease. The dissection of the pathway from the CFTR mutated genotype to the clinical phenotype allowed to identify at least two components of the variability usually found in the genotype–phenotype relationship. One component seems to depend on the genetic variation of CFTR, the other component on the cumulative effect of variations in other genes and cellular pathways independent from CFTR. The experimental dissection of the overall biological CFTR pathway appears to be a powerful approach for a better comprehension of the genotype–phenotype relationship. However, a change from an allele-oriented to a genotypic-oriented view of CFTR genetics is mandatory, as well as a better assessment of sources of variability within the CFTR pathway.     

Clinical and genetic characteristics of cystic fibrosis in CHINESE patients: a systemic review of reported cases

Cystic fibrosis (CF) is a rare disease most commonly seen in Caucasians. Only a few Chinese CF patients have been described in literature, taking into account the large population of China. In this systematic review, we collected the clinical and genetic information of 71 Chinese CF patients based on all available data. Compared with Caucasians, Chinese CF patients often present atypical symptoms, mainly displaying symptoms of pulmonary infection with fewer digestive symptoms. An ethnicity-specific CFTR variant spectrum was also observed in CF patients of Chinese origin, with p.Gly970Asp as the most common mutation while p.Phe508del, the most common pathogenic mutation in CF patients of Caucasian origin, is rare, suggesting the necessity of a Chinese-specific CFTR variant screening panel. Besides, multiplex ligation-dependent probe amplification analysis should be routinely considered, especially for those with unidentified mutations. Potential under-diagnosis of CF in Chinese patients might be caused by a combination of atypical clinical features and genetic heterogeneity in Chinese CF patients, the inaccessibility of sweat and genetic testing facilities, and the one-child policy in China. With the approval of promising small molecule correctors and potentiators, molecular characterization of Chinese-specific CFTR mutations will help to realize more precise treatment for Chinese CF patients.     

Prostaglandin-endoperoxide synthase genesCOX1 andCOX2 — novel modifiers of disease severity in cystic fibrosis patients

Cystic fibrosis (CF) is one of the most common autosomal recessive diseases among Caucasians caused by a mutation in theCFTR gene. However, the clinical outcome of CF pulmonary disease varies remarkably even in patients with the sameCFTR genotype. This has led to a search for genetic modifiers located outside theCFTR gene. The aim of this study was to evaluate the effect of functional variants in prostaglandin-endoperoxide synthase genes (COX1 andCOX2) on the severity of lung disease in CF patients. To the best of our knowledge, it is the first time when analysis ofCOX1 andCOX2 as potential CF modifiers is provided. The study included 94 CF patients homozygous for F508del mutation ofCFTR. To compare their clinical condition, several parameters were recorded, e.g. a unique clinical score: disease severity status (DSS). To analyse the effect of non-CFTR genetic polymorphisms on the clinical course of CF patients, the whole coding region ofCOX1 and selectedCOX2 polymorphisms were analysed. Statistical analysis of genotype-phenotype associations revealed a relationship between the heterozygosity status of identified polymorphisms and better lung function. These results mainly concernCOX2 polymorphisms: −765G>C and 8473T>C. TheCOX1 andCOX2 polymorphisms reducing COX protein levels had a positive effect on all analysed clinical parameters. This suggests an important role of these genes as protective modifiers of pulmonary disease in CF patients, due to inhibition of arachidonic acid conversion into prostaglandins, which probably reduces the inflammatory process.     

High heterogeneity for cystic fibrosis in Spanish families: 75 mutations account for 90% of chromosomes

We have analyzed 640 Spanish cystic fibrosis (CF) families for mutations in the CFTR gene by direct mutation analysis, microsatellite haplotypes, denaturing gradient gel electrophoresis, single-strand conformation analysis and direct sequencing. Seventy-five mutations account for 90.2% of CF chromosomes. Among these we have detected seven novel CFTR mutations, including four missense (G85V, T582R, R851L and F1074L), two nonsense (E692X and Q1281X) and one splice site mutation (711+3A→T). Three variants, two in intronic regions (406-112A/T and 3850-129T/C) and one in the coding region (741C/T) were also identified. Mutations G85V, T582R, R851L, E692X and Q1281X are severe, with lung and pancreatic involvement; 711+3A→T could be responsible for a pancreatic sufficiency/insufficiency variable phenotype; and F1074L was associated with a mild phenotype. These data demonstrate the highest molecular heterogeneity reported so far in CF, indicating that a wide mutation screening is necessary to characterize 90% of the Spanish CF alleles. Received: 3 July 1997 / Accepted: 20 August 1997     

Poor Survival in Rheumatoid Arthritis Associated with Bronchiectasis: A Family-Based Cohort Study

Background

Diffuse bronchiectasis (DB) may occur in rheumatoid arthritis (RA). CFTR (cystic fibrosis transmembrane conductance regulator) mutations predispose RA patients to DB, but the prognosis of RA-associated DB (RA-DB) is unclear.

Methods

We report long-term mortality data from a nationwide family-based association study of patients with RA only, DB only or RA-DB. We assessed mortality as a function of clinical characteristics and CF/CFTR-RD (CFTR-related disorders) mutations in 137 subjects from 24 kindreds. Potential risk factors were investigated by Cox proportional-hazard analysis with shared Gaussian random effects to account for within-family correlations.

Results

During a median follow-up of 11 years after inclusion, 18 patients died, mostly from cardiorespiratory causes. Survival was significantly lower for RA-DB patients than for unaffected relatives and for patients with RA or DB only. RA patients with DB had also a poorer prognosis in terms of survival after RA diagnosis (HR, 8.6; 95% CI, 1.5–48.2; P = 0.014) and from birth (HR, 9.6; 95% CI, 1.1–81.7; P = 0.039). Early onset of DB (HR, 15.4; 95% CI, 2.1–113.2; P = 0.007) and CF/CFTR-RD mutation (HR, 7.2; 95% CI, 1.4–37.1; P = 0.018) were associated with poorer survival in patients with RA-DB. Thus, CF/CFTR-RD mutations in RA patients with early-onset DB defined a subgroup of high-risk patients with higher mortality rates (log-rank test P = 1.28×10⁻⁵).

Conclusion

DB is associated with poorer survival in patients with RA. Early-onset DB and CFTR mutations are two markers that identify RA patients at a high risk of death, for whom future therapeutic interventions should be designed and evaluated.     

CFTR genotype and clinical outcomes of adult patients carried as cystic fibrosis disease

Background

There are nearly 2000 cystic fibrosis transmembrane regulator (CFTR) mutations that cause cystic fibrosis (CF). These mutations are classified into six classes; on the one hand, the first three classes cause severe disease involvement in early childhood, on the other hand, the Class IV, V and VI mutations cause minor severe disease in the same age. Nowadays, with therapeutic advances in CF management and competence of pediatricians, physicians of adults have to deal with two groups of CF patients: (i) adults diagnosed in childhood with severe mutations and (ii) adults who initiated symptoms in adulthood and with Class IV, V and VI mutations. The aim of this study was to analyze adults from a clinical center, treated as CF disease, screening the CFTR genotype and evaluating the clinical characteristics.

Methods

Thirty patients followed as CF disease at the University Hospital were enrolled. After a complete molecular CFTR negative screening and sweat test levels between 40 and 59 mEq/L, five patients were characterized as non-CF disease and were excluded. Molecular screening was performed by CFTR gene sequencing/MLPA or by specific mutation screening. Clinical data was obtained from medical records. The patients were divided into three groups: (1) patients with Class I, II and III mutations in two CFTR alleles; (2) genotype with at least one allele of Class IV, V or VI CFTR mutations and, (3) non-identified CFTR mutation + one patient with one allele with CFTR mutation screened (Class I).

Results

There was an association of CFTR class mutation and sodium/chloride concentration in the sweat test (sodium: p = 0.040; chloride: p = 0.016), onset of digestive symptoms (p = 0.012), lung function parameter (SpO₂ — p = 0.016), Bhalla score (p = 0.021), age at diagnosis (p = 0.008) and CF-related diabetes (p = 0.029). There was an association between Pseudomonas aeruginosa chronic colonization (as clinical marker for the lung disease status) and lung impairment (FEV₁% — p = 0.027; Bhalla score — p = 0.021), CF-related diabetes (p = 0.040), chloride concentration in the sweat test (p = 0.040) and chronic infection by microorganisms (Staphylococcus aureus — p = 0.039; mucoid P. aeruginosa — p = 0.001). There is no positive association with the status of other clinical markers and the CFTR genotype groups. For clinical association with pancreatic insufficiency (as clinical marker for digestive symptoms), no association was related.

Conclusion

The adults with CF diagnosed by sweat test have specific clinical and genotypic characteristics, being a population that should be studied to cause better future management. Some patients treated as CF disease by clinical symptoms, showed no disease, taking into account the sweat test and complete exon sequencing/MLPA screening.