High throughput AS LNA qPCR method for the detection of a specific mutation in poliovirus vaccine strains

Sabin Inactivated Poliovirus Vaccine (sIPV) has become one of the preferred vaccination options for the last step in the Poliovirus eradication program. Sequencing of poliovirus samples is needed during the manufacturing of poliovirus vaccines to assure the safety and immunogenicity of these vaccines. Next-generation sequencing analysis is the current costly and time-consuming gold standard for monitoring the manufacturing processes. We developed a low-cost and quick, highly sensitive, and allele-specific locked nucleic acid-probe-based reverse transcription quantitative PCR alternative that can accurately detect mutations in poliovirus vaccine samples during process development, scaling up, and release. Using the frequently in vitro occurring and viral replication-impacting VP1-E295K mutation as a showcase, we show that this technology can accurately detect E295K mutations in poliovirus 2 samples to similar levels as NGS. The qPCR technology was developed employing a synthetic dsDNA fragment-based standard curve containing mixes of E295K-WT (wildtype) and Mut (mutant) synthetic dsDNA fragments ranging from 1 × 107 copies/µL to 1 × 102 copies/µL to achieve a linear correlation with R2 > 0.999, and PCR efficiencies of 95-105 %. Individual standard concentration levels achieved accuracies of ≥92 % (average 96 %) and precisions of ≤17 % (average 3.3 %) RSD. Specificity of locked nucleic acid (LNA)-probes was confirmed in the presence and absence of co-mutations in the probe-binding region. Application of the developed assay to Sabin Poliovirus type 2 production run samples, illustrated a linear relationship with an R2 of 0.994, and an average accuracy of 97.2 % of the variant (allele)-specific AS LNA qPCR result, compared to NGS. The assay showed good sensitivity for poliovirus samples, containing E295K mutation levels between 0 % and 95 % (quantification range). In conclusion, the developed AS LNA qPCR presents a valuable low-cost, and fast tool, suitable for the process development and quality control of polio vaccines.

[Lung transplantation in cystic fibrosis--a position paper]

Lung transplantation in cystic fibrosis is an established therapy, due to the fact that vast majority of adult CF patients will develop respiratory failure. Even adolescents and children can be transplanted successfully today. Lung transplantation in cystic fibrosis requires special consideration concerning candidate selection, surgery and postoperative follow-up care. Due to a donor shortage and increasing waiting time, early referral to transplant centres of potential candidates is crucial. In the process of candidate selection, assumed improvements in quality of life and survival benefit should be weighed against contraindications. Centre-based follow-up and close cooperation with local physicians are key factors for success. During follow-up care, the transplantation team should be contacted immediately in the case of any problem or change in medication.

Respiratory viral infections within one year after pediatric lung transplant

Abstract: To characterize epidemiology and risk factors for respiratory viral infections (RVI) in pediatric lung transplant recipients within the first post‐transplant year, a retrospective multicenter study of pediatric lung transplant recipients from 1988 to 2005 was conducted at 14 centers in the United States and Europe. Data were recorded for 1 year post transplant. Associations between RVI and continuous and categorical risk factors were assessed using Wilcoxon's rank‐sum and χ² tests, respectively. Associations between time to RVI and risk factors or survival were assessed by multivariable Cox proportional hazards models. Of 576 subjects, 79 subjects (14%) had 101 RVI in the first year post transplant. Subjects with RVI were younger than those without RVI (median ages 9.7, 13; P<0.01). Viruses detected included adenovirus (n=25), influenza (n=9), respiratory syncytial virus (n=21), parainfluenza virus (n=19), enterovirus (n=4), and rhinovirus (n=22). In a multivariable model for time to first RVI, etiology other than cystic fibrosis (CF), younger age, and no induction therapy were independently associated with risk of RVI. Cytomegalovirus serostatus and acute rejection were not associated with RVI. RVI was independently associated with decreased 12‐month survival (hazard ratio 2.6, 95% confidence interval 1.6–4.4). RVI commonly occurs after pediatric lung transplantation with risk factors including younger age and non‐CF diagnosis. RVI is associated with decreased 1‐year survival.

Transient correction of the basic defect in sweat glands in an individual with cystic fibrosis carrying the complex CFTR allele F508del-R553Q

The molecular pathology of mutant F508del CFTR is partially corrected in vitro by the secondary amino acid substitution R553Q in the ABC signature motif. An individual with the CFTR genotype R553X/F508del-R553Q showed the typical symptoms and electrophysiological anomalies of cystic fibrosis in the airways and intestine. Sweat chloride concentrations were normal early in life, but were later raised into the range that is diagnostic for cystic fibrosis, suggesting that R553Q could temporarily correct the basic defect in sweat glands. R553Q caused a delay in diagnosis because of false negative sweat tests but was not a disease reverting suppressor mutation as had been inferred from cellular models.

A novel sidestream ultrasonic flow sensor for multiple breath washout in children

OBJECTIVE

Inert gas multiple breath washout (MBW) for measuring Lung Clearance Index using mass spectrometry and 4% sulfur hexafluoride (SF(6)) as the tracer gas has been shown to be sensitive for detecting early Cystic Fibrosis (CF) lung disease. However, mass spectrometry requires bulky equipment and is expensive to buy and maintain. A novel sidestream ultrasonic device may overcome this problem. The aims of this study were to assess the feasibility and clinical validity of measuring lung volume (functional residual capacity, FRC) and the LCI using the sidestream ultrasonic flow sensor in children and adolescents with CF in relation to spirometry and plain chest radiographs.

PATIENTS AND METHODS

MBW using the sidestream ultrasonic device and conventional spirometry were performed in 26 patients with CF and 22 healthy controls.

RESULTS

In the controls (4.7-17.7 years) LCI was similar to that reported using mass spectrometry (mean (SD) 6.7 (0.5)). LCI was elevated in 77% of the CF children (6.8-18.9 years), whereas spirometry was abnormal in only 38.5%, 61.5%, and 26.9% for FEV(1), MEF(25), and FEV(1)/FVC, respectively. This was more marked in children <10 years. LCI correlated with the Crispin-Norman score, whereas FEV(1) did not.

CONCLUSIONS

Sidestream ultrasonic MBW is a valid and simple alternative to mass spectrometry for assessing ventilation homogeneity in children.

Physical activity is independently related to aerobic capacity in cystic fibrosis

It is unclear whether a relationship between physical activity (PA) and maximal oxygen uptake (V'(O2,max)) exists in cystic fibrosis (CF) and, if so, whether the relationship reflects a direct effect or is mediated by the effects of confounding variables, such as pulmonary or muscle function. The objective of the present study was to determine the relationship between PA and V'(O2,max) in CF while adjusting for possible influences of confounding factors. In total, 36 female and 35 male patients with CF from Germany and Switzerland (aged 12-40 yrs, forced expiratory volume in one second (FEV1) 25-107% predicted) were studied. A Wingate test was employed to measure muscle power. PA was monitored for 7 days and expressed in two ways: 1) average daily accelerometer count (ADAC) and 2) time spent in moderate-to-vigorous PA (MVPA). V'(O2,max) was determined during an incremental cycle exercise test to volitional fatigue. PA was positively related to V'(O2,max). In a multiple linear regression analysis, height, sex, FEV1, muscle power and ADAC (additionally explained variance 2.5%) or time spent in MVPA (additionally explained variance 3.7%) were identified as independent predictors of V'(O2,max). In conclusion, high levels of physical activity in addition to good muscular and pulmonary functions are associated with a high aerobic capacity in cystic fibrosis.

Cystic fibrosis in 65- and 67-year-old siblings. Clinical feature and nasal potential difference measurement in patients with genotypes F508del and 2789+5G-->A

Cystic fibrosis (CF) is a recessive genetic disease caused by defects of the cystic fibrosis trans-membrane regulator (CFTR) gene with a median survival of less than 35 years. This work reports on the oldest living German siblings with CF. Besides clinical history, CF genotype and nasal potential difference (NPD) measurement results, the remarkably high exercise activity of the siblings is discussed as a disease-modifying factor. Both male patients have an overall mild pulmonary manifestation. They have suffered from abdominal symptoms since their early childhood, including recurrent pancreatitis and diffuse symptoms leading to partial gastric resection. They were diagnosed as having CF with positive sweat tests at the advanced ages of 45 and 43 years, respectively. Later on genotyping revealed compound heterozygosity for F508del and 2789+5G-->A. Using NPD we demonstrated a CF-typical inhibition of the NPD by the Na channel blocker amiloride, although in both siblings the remaining CFTR function and alternate chloride channel function were detected during superfusion of the nasal epithelium with isoproterenol and ATP. Long-term survival with CF is basically influenced by the CFTR genotype. The patients' genotype was discussed as a mild one with remaining CFTR function. We demonstrated this residual CFTR function in both siblings using NPD. Additionally the siblings' continuous healthy lifestyle and their engagement in a remarkably high level of exercise activities from early childhood to the present possibly have an important effect on the long-term outcome of CF as disease-modifying factors. In this regard this report can encourage CF patients to maintain a high level of physical activity in their daily lives.

New criteria for impaired fasting glucose and screening for diabetes in cystic fibrosis

Cystic fibrosis-related diabetes mellitus (CFRD) is the most frequent comorbidity in cystic fibrosis. Its clinical relevance is stressed by the association with increased mortality, and decreased pulmonary and nutritional status. An annual oral glucose tolerance test (OGTT) is recommended as a screening test for CFRD, but this is often not realised because of its time- and resource-consuming nature. Therefore, alternative approaches are welcome. In 2003, the American Diabetes Association (ADA) lowered the cut-off point separating normal from elevated fasting plasma glucose from <6.1 mmol x L(-1) to <5.6 mmol x L(-1), suggesting the performance of an OGTT only in those with impaired fasting glucose (IFG; range 5.6-6.0 mmol x L(-1)). The current authors tested whether this approach was reliable for the early identification of patients with CFRD. OGTTs from 1,128 patients (53% males; 47% females; median age 17.1 yrs) were available for analysis. A total of 101 (8.9%) OGTTs were classified as diabetic. The new ADA criteria for IFG increased the sensitivity to 82% (versus 65%) and decreased the specificity to 70% (versus 94%) compared with the old criteria used to identify patients with diabetic OGTTs. In conclusion, the American Diabetes Association approach of using impaired fasting glucose as an indication for performing selective oral glucose tolerance tests is definitely unsuitable when aiming at the early identification of patients with cystic fibrosis-related diabetes mellitus, and it cannot replace annual oral glucose tolerance tests.

Hygienemaßnahmen für Patienten mit Cystischer Fibrose

BACKGROUND

Respiratory tract infections significantly contribute to morbidity and mortality of cystic fibrosis patients.

METHODS

We conducted a systematic literature review (Pubmed 01/1966 up to 09/2003) in order to present recommendations for the isolation of CF patients colonized with Burkholderia cepacia spp., Pseudomonas aeruginosa, Stenotrophomonas maltophilia and Alcaligenes spp. Evidence and quality of 64 publications dealing with pathogen transmission or isolation measurements of colonized patients were evaluated.

RESULTS

B. cepacia spp. was dealt most often with and 35 of 36 authors recommended the isolation of patients colonized with this pathogen. Isolation of patients colonized with P. aeruginosa was proposed by 21 of 25 authors. Only 5 studies concerned S. maltophilia or Alcaligenes spp.

CONCLUSIONS

A) B. cepacia spp. colonized patients need to get a single room for their own. B) P. aeruginosa colonized CF patients should be separated from non-colonized CF patients. C) Patients harbouring even multi drug resistant P. aeruginosa, S. maltophilia or Alcaligenes spp. may not share their room with immunocompromised patients and should also be isolated when treated in intensive care units.

Low-dose methotrexate for advanced pulmonary disease in patients with cystic fibrosis

Inflammation is a hallmark in the pathogenesis of pulmonary destruction in cystic fibrosis (CF). There is no proven effective systemic anti-inflammatory treatment for CF patients with advanced pulmonary disease. Methotrexate (MTX) is known as an effective anti-inflammatory treatment in asthma and in juvenile rheumatoid arthritis. The question was: Is an improvement in pulmonary function achievable with low-dose MTX in patients with cystic fibrosis and advanced pulmonary disease.?

METHODS

We treated five CF patients with advanced pulmonary disease, who deteriorated in spite of intensive conventional therapy on an individual basis with low-dose MTX. FEV1% and immunoglobulin G (IgG) serum levels were followed from the year before to the year after starting with MTX.

RESULTS

In the year before starting with MTX, FEV1% decreased (median: 10% FEV1; range 9-15% FEV1; P<0.005) after starting with MTX, FEV1% increased (median: 9% FEV1; range: 2-15% FEV1; P<0.05). IgG changed (median: -2 g/l; range: 0.2 to -7.3 g/l) in the first year with MTX.

CONCLUSION

These preliminary data suggest a beneficial effect of MTX even in advanced pulmonary disease in CF patients and supports the need for a controlled prospective study.

Chloride conductance and genetic background modulate the cystic fibrosis phenotype of Delta F508 homozygous twins and siblings

To investigate the impact of chloride (Cl(-)) permeability, mediated by residual activity of the cystic fibrosis transmembrane conductance regulator (CFTR) or by other Cl(-) channels, on the manifestations of cystic fibrosis (CF), we determined Cl(-) transport properties of the respiratory and intestinal tracts in Delta F508 homozygous twins and siblings. In the majority of patients, cAMP and/or Ca(2+)-regulated Cl(-) conductance was detected in the airways and intestine. Our finding of cAMP-mediated Cl(-) conductance suggests that, in vivo, at least some Delta F508 CFTR can reach the plasma membrane and affect Cl(-) permeability. In respiratory tissue, the expression of basal CFTR-mediated Cl(-) conductance, demonstrated by 30% of Delta F508 homozygotes, was identified as a positive predictor of milder CF disease. In intestinal tissue, 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid-insensitive (DIDS-insensitive) Cl(-) secretion, which is indicative of functional CFTR channels, correlated with a milder phenotype, whereas DIDS-sensitive Cl(-) secretion was observed mainly in more severely affected patients. The more concordant Cl(-) secretory patterns within monozygous twins compared with dizygous pairs imply that genes other than CFTR significantly influence the manifestation of the basic defect.

Diabetes mellitus in patients with cystic fibrosis: the impact of diabetes mellitus on pulmonary function and clinical outcome

In this multicenter study, the impact of CF-related diabetes mellitus (CFRD) on pulmonary function and clinical outcome has been investigated. To better characterize the relationship between insulin deficiency and clinical outcome we prospectively followed a group of 56 CF patients, 28 with CFRD (group 1) and 28 without diabetes (group 2) for 5 years. The clinical course of the patients was registered at each center. Data included were mortality, pulmonary function, body mass index, in-patient treatment, and CF-typical and diabetes typical complications. At the end of the study nearly twice the number of patients had died in group 1 as compared to group 2, however due to the low patient number this did not reach statistical significance. In patients with diabetes FEV1 and FVC declined significantly over the five year study period, whereas patients without diabetes did not show a significant decline during the study period. Retinopathy, nephropathy, and neuropathy were only observed in diabetic patients. In conclusion, the data presented in this prospective, multicenter study give evidence that insulin deficiency leads to a direct decline in pulmonary function suggesting a cause and effect relationship between insulin deficiency and lung disease.

Categories of deltaF508 homozygous cystic fibrosis twin and sibling pairs with distinct phenotypic characteristics

Cystic fibrosis (CF), the most common severe autosomal recessive trait among Caucasians, is caused by molecular lesions in the cystic fibrosis transmembrane conductance regulator gene (CFTR). The course of the multi-organ disease CF is highly variable, suggesting the influence of environmental factors and/or modulating genes other than CFTR on the disease phenotype. To evaluate the cause of CF disease variability, the European CF Twin and Sibling Study collected data on two clinical parameters most sensitive for the course and prognosis of CF, ie weight predicted for height (wfh)% (representative for the nutritional status) and FEVPerc (representative for the pulmonary status) for a cohort of 277 sibling pairs, 12 pairs of dizygous twins and 29 pairs of monozygous twins. Of these 318 CF twin and sib pairs, 114 were reported to be homozygous for the most frequent CF disease-causing lesion, deltaF508. Intra-pair discordance was assessed by the intra-pair differences with wfh% and FEVPerc and by DELTA, a composite parameter defined by linear combination of wfh% and FEVPerc in order to describe discordance with respect to the overall disease severity. Monozygous twins had a significantly lower DELTA than dizygous twins (P = 0.05) indicating that CF disease severity is modulated by an inherited component in addition to the CFTR gene itself. Extreme phenotypes are considered to be more informative for the analysis of any quantitative trait. Thus, we aimed to quantify disease severity and intra-pair discordance in order to select pairs with the extreme phenotypes DIS (discordant patient pairs), CON+ (concordant and mildy affected patient pairs) and CON- (concordant and severely affected patient pairs). The algorithm reliably discriminated between pairs DIS, CON+ and CON- among the cohort of deltaF508 homozygotes. The selected pairs from these categories demonstrated non-overlapping properties for wfh%, FEVPerc and the intra-pair difference of both parameters.

Mutations of the cystic fibrosis gene, but not cationic trypsinogen gene, are associated with recurrent or chronic idiopathic pancreatitis

OBJECTIVE

We investigated whether mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene and cationic trypsinogen gene are associated with recurrent acute, or chronic idiopathic pancreatitis.

METHODS

Twenty patients with idiopathic pancreatitis (11 women, nine men; mean age, 30 yr) were studied for the presence of a CFTR mutation by screening the genomic DNA for more than 30 mutations and variants in the CFTR gene. Selected mutations of the cationic trypsinogen gene were screened by Afl III restriction digestion or by a mutation-specific polymerase chain reaction (PCR). In each patient exons 1, 2, and 3 of the cationic trypsinogen gene were sequenced. Patients with a CFTR mutation underwent evaluation of further functional electrophysiological test (intestinal current measurement).

RESULTS

No mutation of the cationic trypsinogen gene was detected. A CFTR mutation was detected in 6/20 (30.0%) patients. Three patients (15.0%) had a cystic fibrosis (CF) mutation on one chromosome (deltaF508, I336K, Y1092X), which is known to cause phenotypical severe cystic fibrosis. One patient was heterozygous for the 5T allele. In addition, two possibly predisposing CFTR variants (R75Q, 1716G-->A) were detected on four patients, one of these being a compound heterozygous for the missense mutation I336K and R75Q. No other family member (maternal I336K; paternal R75Q; sister I1336K) developed pancreatitis. An intestinal current measurement in rectum samples of patients with a CFTR mutation revealed no CF-typical constellations.

CONCLUSIONS

CFTR mutations are associated with recurrent acute, or chronic idiopathic pancreatitis, whereas mutations of the cationic trypsinogen mutation do not appear to be a frequent pathogenetic factor.

Residual chloride secretion in intestinal tissue of deltaF508 homozygous twins and siblings with cystic fibrosis. The European CF Twin and Sibling Study Consortium

BACKGROUND & AIMS

Cholinergic stimulation of chloride secretion is impaired in the intestines of patients with cystic fibrosis (CF). However, intestinal chloride secretion has been observed in patients with mild CF mutations. The aim of this study was to investigate residual Cl(-) secretion in the intestine of DeltaF508 homozygous CF patients, and examine the contribution of cystic fibrosis transmembrane conductance regulator (CFTR) and alternative Cl(-) conductances. Twins and siblings with identical CFTR genotypes were investigated to determine the impact of factors other than CFTR on chloride secretion.

METHODS

Chloride secretion in rectal tissue was investigated by applying Ca(2+) and adenosine 3',5'-cyclic monophosphate (cAMP)-linked agonists before and after the inhibition of alternative Cl(-) conductances with 4,4'-diisothiocyanostilbene-2, 2'-disulfonic acid (DIDS).

RESULTS

cAMP-mediated Cl(-) secretion was observed in 73% of patients, and 20% showed DIDS-sensitive Ca(2+)-activated Cl(-) secretion. This DIDS-sensitive alternative chloride conductance was seen only in CF patients who also responded to cAMP agonists. Chloride secretion was more concordant within monozygous twins than within dizygous pairs.

CONCLUSIONS

These results suggest the presence of CFTR-mediated Cl(-) secretion in a subgroup of patients, implying that a portion of deltaF508 CFTR can be processed in vivo and function as a chloride channel in the apical membrane of intestinal cells. Moreover, a considerable number of deltaF508 homozygous patients express chloride conductances other than CFTR in their intestinal epithelia.

Fractional analysis of bronchoalveolar lavage fluid cytology in cystic fibrosis patients with normal lung function. Bronchoalveolar lavage for the evaluation of anti-inflammatory treatment (BEAT) study group

Cystic fibrosis (CF) is associated with a neutrophil dominated airway inflammation. So far bronchoalveolar lavage (BAL) studies in CF have used pooled BAL samples which may be more representative of the alveolar compartment rather than the airways. To assess whether the first sample of a BAL is more sensitive in the evaluation of airway inflammation, the authors have studied 105 stable CF patients aged 5-37 yrs with a mean forced expiratory volume in one second (FEV1) of 96+/-15% (mean+/-SD). BAL cytology of the first and pooled samples were compared to reference values obtained in children without respiratory disease. Absolute cell counts and the percentage of neutrophils were significantly increased in CF patients. If the 95% confidence interval was used as a cut-off point, 17/105 CF patients had a normal percentage of neutrophils in pooled BAL samples, but only three also had a normal percentage of neutrophils in the first BAL aliquot. Therefore, neutrophil dominated airway inflammation is more pronounced in the first, mainly bronchial, bronchoalveolar lavage sample suggesting that sequential analysis of bronchoalveolar lavage fluid may have a higher sensitivity to detect early inflammatory changes in CF patients.

Clinical presentation of exclusive cystic fibrosis lung disease

The diagnosis of cystic fibrosis (CF) is based on the occurrence of two mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene and on assays that measure the basic defect of abnormal chloride transport in the affected organs. However, in cases of atypical CF not all diagnostic tests may be positive. We present a patient with an atypical CF phenotype in whom the only presenting symptom was severe CF-like lung disease substantiated by an abnormal nasal potential difference. Genetic analysis showed that the patient was a symptomatic heterozygote, which suggests that one lesion in the CFTR gene may be sufficient to cause CF-like lung disease.

Long-term follow up of changes in FEV1 and treatment intensity during Pseudomonas aeruginosa colonisation in patients with cystic fibrosis

BACKGROUND

Colonisation with Pseudomonas aeruginosa (PA) is a striking feature of lung involvement in cystic fibrosis. To identify the clinical consequences of the different steps of colonisation with PA under a defined therapeutic regime (no prophylactic antibiotic treatment as long as patients had no severe pulmonary disease), their influence on pulmonary function and on therapeutic intensity was examined.

METHODS

Forty patients with cystic fibrosis were followed from first detection of PA (PA1), chronic PA colonisation (PAc), first mucoid PA detection (PAm), to chronic mucoid PA colonisation (PAcm). Percentage predicted forced expiratory volume in one second (FEV1), the number of intravenous antibiotic treatment courses, and the percentage of patients on inhaled antibiotics were followed retrospectively and longitudinally in relation to the different steps of PA colonisation. The annual changes in FEV1 and therapeutic intensity in the two years preceding each step were compared with the two years following each step. Changes in FEV1 were related to therapeutic intensity.

RESULTS

The mean (SD) annual changes in FEV1 (% predicted) worsened significantly only with the transition to the mucoid stages (PAm: 4.6 (13.2) versus -4.3 (8.1); PAcm: 7.3 (12.0) versus -4.8 (7.4)) with a mean difference (95% CI) between before and after the transition of 8.9 (2.6 to 15.2) for PAm and 12.1 (6.4 to 17.6) for PAcm. With non-mucoid PA stages the therapeutic intensity increased in the year of transition and with mucoid PA stages it increased in the years following transition. Therapeutic intensity was unrelated to changes in FEV1.

CONCLUSION

With the treatment regime used an accelerated decrease in FEV1 was successfully prevented in the non-mucoid stages but not in the mucoid stages of PA colonisation.

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.