Genetic and clinical features of false-negative infants in a neonatal screening programme for cystic fibrosis

A study was performed on the delayed diagnosis of cystic fibrosis (CF) in infants who had false-negative results in a neonatal screening programme. The genetic and clinical features of false-negative infants in this screening programme were assessed together with the efficiency of the screening procedure in the Lombardia region. In total, 774 687 newborns were screened using a two-step immunoreactive trypsinogen (IRT) (in the years 1990-1992), IRT/IRT + delF508 (1993-1998) or IRT/IRT + polymerase chain reaction (PCR) and oligonucleotide ligation assay (OLA) protocol (1998-1999). Out of 196 CF children born in the 10 y period 15 were false negative on screening (7.6%) and molecular analysis showed a high variability in the genotypes. The cystic fibrosis transmembrane regulator (CFTR) gene mutations identified were delF508, D1152H, R1066C, R334W, G542X, N1303K, F1052V, A120T, 3849 + 10kbC →T, 2789 + 5G →A, 5T-12TG and the novel mutation D110E. In three patients no mutation was identified after denaturing gradient gel electrophoresis of the majority of CFTR gene exons.

Conclusion: The clinical phenotypes of CF children diagnosed by their symptoms at different ages were very mild. None of them presented with a severe lung disease. The majority of them did not seem to have been damaged by the delayed diagnosis. The combination of IRT assay plus genotype analysis (1998-1999) appears to be a more reliable method of detecting CF than IRT measurement alone or combined with only the delF508 mutation.     

CFTR pharmacological modulators: A great advance in cystic fibrosis management

Cystic fibrosis is a severe monogenic disease that affects around 7400 patients in France. More than 2100 mutations in the cystic fibrosis conductance transmembrane regulator (CFTR), the gene encoding for an epithelial ion channel that normally transports chloride and bicarbonate, lead to mucus dehydration and impaired bronchial clearance. Systematic neonatal screening in France since 2002 has enabled early diagnosis of cystic fibrosis. Although highly demanding, supportive treatments including daily chest physiotherapy, inhaled aerosol therapy, frequent antibiotic courses, nutritional and pancreatic extracts have improved the prognosis. Median age at death is now beyond 30 years. Ivacaftor was the first CFTR modulator found to both reduce sweat chloride concentration and improve pulmonary function in the rare CFTR gating mutations. Combinations of modulators such as lumacaftor + ivacaftor or tezacaftor + ivacaftor were found to improve pulmonary function both in patients homozygous for the F508del mutation characterized by the lack of CFTR protein and those heterozygous for F508del with minimal CFTR activity. The triple combination of ivacaftor + tezacaftor + elexacaftor was recently shown to significantly improve pulmonary function and quality of life, to normalize sweat chloride concentration, and to reduce the need for antibiotic therapy in patients with at least one F508del mutation (83% in France). These impressive data, however, need to be confirmed in the long term. Nevertheless, it is encouraging to hear treated patients testify about their markedly improved quality of life and to observe that the number of lung transplants for cystic fibrosis decreased dramatically in France after 2020, despite the COVID pandemic, with no increase in deaths without lung transplant.     

Faecal elastase-1 concentration in cystic fibrosis patients with CFTR I1234V mutation

Aim: To assess the exocrine pancreatic function among cystic fibrosis patients with cystic fibrosis trans-membrane conductance regulator (CFTR) I1234V mutation. Methods: Cross-sectional study of 40 cystic fibrosis patients with homozygous CFTR I1234V mutation belonging to a large Arab kindred family and 25 healthy subjects as a control group over a period of 12 mo. Assessment of their exocrine pancreatic function was performed by measuring faecal elastase-1 (FE1) concentration with a commercial ELISA kit using polyclonal antibodies (BioServ Diagnostics) in CF patients compared to healthy subjects. The results were compared with those obtained from a second laboratory using another commercial ELISA (ScheBo; Biotech, Germany) that uses two monoclonal antibodies against different specific epitopes of human pancreatic elastase. Results: All CF patients with CFTR I1234V mutation had normal levels of faecal elastase 1. No significant difference was found between the two methods for the CF groups or between the CF patients with and without pancreatic enzyme replacement.

Conclusion: Cystic fibrosis with homozygous CFTR I1234V mutation is associated with pancreatic sufficiency. Assessment of exocrine function using polyclonal antibodies does not significantly differ from that using two monoclonal antibodies against different specific epitopes of human pancreatic elastase.     

Airway mucus in cystic fibrosis

Defective expression and function of the cystic fibrosis transmembrane conductance regulator (CFTR) in cystic fibrosis (CF) airway epithelial cells are associated with airway mucus hypersecretion, inflammation and infection that begin early in life and lead, at an advanced stage of the disease, to severe airway obstruction with hyperviscous and adhesive airway mucus. Whether the abnormalities of airway mucus are already present at birth before infection is debatable. In CF, the impaired Cl(-) and HCO(3)(-) secretion associated with increased epithelial Na(+) absorption results in dehydration of airway mucus, decreased antimicrobial functions and impaired mucociliary clearance. Alterations in antibacterial peptide function, as well as the increased mucin expression and secretion (MUC 5AC and MUC 5B), are important biochemical factors responsible for the propensity for infection in CF airways. Alterations in mucin and lipid composition induce an increased viscosity and adhesiveness to the airways that can affect the mucociliary and cough transport. The increased content of pro-inflammation cytokines such as interleukin-8 (IL-8) suggest that, before infection, airway inflammation occurs very early in CF. The development of non-invasive techniques and humanised animal models (xenografts) represents a major opportunity to identify early abnormalities in CF airway mucus.     

Phenotypic and genetic characterization of patients with features of "nonclassic" forms of cystic fibrosis

OBJECTIVE: To determine which features of incomplete or "nonclassic" forms of cystic fibrosis (CF) are associated with deleterious CF transmembrane conductance regulator gene ( CFTR ) mutations, and to explore other etiologies for features not associated with deleterious CFTR mutations. STUDY DESIGN: Clinical features were compared between 57 patients with deleterious mutations in each CFTR and 63 with no deleterious mutations. The Shwachman Bodian Diamond syndrome gene ( SBDS ) was sequenced to search for mutations in patients with no deleterious CFTR mutations and steatorrhea to determine if any had unrecognized Shwachman-Diamond syndrome (SDS). RESULTS: The presence of a common CF-causing mutation, absence of the vas deferens, and Pseudomona aeruginosa in the sputum correlated with the presence of two deleterious CFTR mutations, whereas sweat chloride concentration, diagnostic criteria for CF, and steatorrhea did not. However, sweat chloride concentration correlated with CFTR mutation status in patients infected with P aeruginosa. One patient had disease-causing mutations in each SBDS . CONCLUSIONS: Presence of a common CF-causing mutation, absence of the vas deferens and/or P aeruginosa infection in a patient with features of nonclassic CF are predictive of deleterious mutations in each CFTR , whereas steatorrhea in the same context is likely to have etiologies other than CF transmembrane conductance regulator (CFTR) dysfunction.     

Growth and nutritional indexes in early life predict pulmonary function in cystic fibrosis

OBJECTIVE: To determine the relation of growth and nutritional status to pulmonary function in young children with cystic fibrosis (CF). STUDY DESIGN: The relation of weight-for-age (WFA), height-for-age (HFA), percent ideal body weight (%IBW), and signs of lung disease at age 3 years with pulmonary function at age 6 years was assessed in 931 patients with CF. Associations of changes in WFA from age 3 to 6 on pulmonary function were also assessed. RESULTS: WFA, HFA, and %IBW were poorly associated with lung disease at age 3 years, but all were strongly associated with pulmonary function at age 6 years. Those with WFA below the 5th percentile at age 3 had lower pulmonary function at age 6 compared with those above the 75th percentile (FEV(1): 86 +/- 20 [SD] versus 102 +/- 18 % predicted, respectively). Pulmonary function was highest in those whose WFA remained >10th percentile from age 3 to 6 (FEV(1): 100 +/- 19 % predicted) and lowest in those who remained <10th percentile (84 +/- 21 % predicted). Patients with signs and symptoms of lung disease at age 3 years had lower pulmonary function at age 6 years. CONCLUSIONS: Aggressive intervention early in life aimed at growth and nutrition and/or lung disease may affect pulmonary function.     

Chronic lung disease and cystic fibrosis phenotype in prolidase deficiency: a newly recognized association

Six families with prolidase deficiency (PD) and chronic lung disease are reported, a previously unrecognized association. In one family with a classic cystic fibrosis (CF) phenotype, no evidence for CF Transmembrane Conductance Regulator (CFTR)-related mutations could be found. Chronic lung disease and CFTR-mutation negative CF may be associated with PD.     

Profile and factors determining outcome in a cohort of cystic fibrosis patients seen at the Aga Khan University Hospital, Karachi, Pakistan

Cystic fibrosis is the most common potentially lethal autosomal recessive, genetic disease associated with pulmonary and pancreatic insufficiency. It is caused by variations in the CFTR (cystic fibrosis transmembrane regulator) gene. The most common mutation in the CFTR gene designated DeltaF508, is found in only 33 per cent of CF patients in Pakistan. The variability in presentation and clinical severity of disease may be a function of genotypic-phenotypic factors. Our aim was to attempt to define the disease in this region and to lay the ground work for future mutational analysis. This study was a retrospective chart review was conducted to identify cystic fibrosis patients seen at the Aga Khan University Hospital over a 10-year period. Our study identified 56 patients diagnosed by a pilocarpine iontophoresis sweat test. A chart review was then done to look at the various clinical profiles. 58.3 per cent of our patients presented in the first 6 months of life supporting the hypothesis that CF may be a severe disease in Asians with an earlier age of presentation. Most of the patients (80.6 per cent) presented with pulmonary problems while 83.9 per cent had failure to thrive. The most frequently isolated pathogen was Pseudomonas aeruginosa in 87.5 per cent of the patients tested. 70 per cent of the patients died in the first year of life. The clinical parameters studied suggest a severe form of CF in Pakistani patients and provides a foundation for future studies to define genotype/phenotype correlations of the specific mutations involved in Pakistani CF patients.     

Allergic bronchopulmonary aspergillosis in paediatric cystic fibrosis patients

Allergic bronchopulmonary aspergillosis (ABPA) is a severe complication in children, adolescents and adults with cystic fibrosis (CF), the prevalence of which ranges from 6-25%. The disease is the result of the colonisation of the respiratory tract by fungi of the genus Aspergillus, commonly Aspergillus fumigatus, and subsequent host sensitisation to fungal antigens, accompanied by a Th2 CD4 type response mediated by the production of specific IgE. The consequent inflammatory and obstructive bronchopulmonary injury can progress to fibrosis. The diagnosis should be considered early in patients with CF who show wheezing, transient pulmonary infiltrates and reduced lung function. The objective diagnosis is not straightforward because of overlapping clinical and radiological signs, particularly the progression of bronchiectasis. Specific criteria are needed for the diagnosis of ABPA in patients with CF, such as those proposed by the Cystic Fibrosis Foundation. The study of specific IgE against recombinant antigens of A. fumigatus has contributed to the early diagnosis of ABPA with high sensitivity and specificity. The technique has also shown promise in the follow-up of patients after steroid therapy and the early detection of recurrences. Treatment consists of long-term systemic corticosteroid usage, the monitoring of their adverse effects, and of the measurement of total serum IgE levels. The concomitant use of oral itraconazole seems to promote a better control of the disease and to reduce the duration of systemic steroid therapy but its use continues to be controversial. Controlled studies involving larger numbers of patients are necessary if we are to better understand the management of ABPA.     

CFTR gene analyis in 207 patients with cystic fibrosis in southwest France: high frequency of N1303K and 1811+1.6bA>G mutations]

The large molecular heterogeneity in cystic fibrosis (CF) represents the main difficulty for the genotype characterization. Moreover, numerous studies have reported considerable variations in frequencies of cystic fibrosis transmembrane conductance regulator (CFTR) mutations in different populations. MATERIAL AND METHODS: We analyzed the genotype of 207 CF children living in southwest France. RESULTS: Among 50 identified mutations, we report for some of them a widely modified incidence compared with those observed in other regions of France. These differences were more significant in the subset of the CF chromosomes originating in southwest France. Thus, the 1811 + 1.6 kbA > G mutation, rarely observed in the other French regions (< 0.5%), proved to be, with a frequency of 8.8%, the most frequent mutation after the F508 deletion (57%). The frequencies of N1303K, 1811 + 1.6 kbA > G and R334W mutations were also clearly increased: 7.9 and 2.6%, respectively. CONCLUSION: We show that the southwest of France is characterized by a specific mutational spectrum. We consider that these regional data on the spectrum of CF mutations are crucial to develop more accurate and less expensive molecular screening strategies for cystic fibrosis in France.     

Diabetes in an infant with cystic fibrosis

Cystic fibrosis (CF)-related diabetes mellitus is an unusual complication in very young pediatric patients with CF. It is generally associated with more severe clinical manifestations of CF. In this report, we describe a case of diabetes and CF starting in infancy. The patient manifested a form of intermittent diabetes without fasting hyperglycemia, which was exacerbated by steroid treatment during pulmonary disease and occasionally required insulin therapy. Insulin responses to oral and intravenous glucose challenge were low. The clinical and radiological status was stable during the 9-yr follow-up. Our patient demonstrates that diabetes may not only represent a complication of CF, as previously maintained, but can also be a co-morbid condition proceeding along with the exocrine disease. The early occurrence of hyperglycemia in this case may highlight an impairment of beta-cell function, which might be genetically determined. Careful monitoring of the glucose profile and of beta-cell function is indicated in patients with CF to avoid late recognition of diabetes.     

The need for vigilance: the case of a false-negative newborn screen for cystic fibrosis

Cystic fibrosis (CF) is the most common life-limiting recessive genetic disorder in the white population. CF is caused by abnormalities in the gene that codes for the cystic fibrosis transmembrane conductance regulator protein (CFTR) and may result in severe chronic lung disease, poor growth, and malnutrition. Physicians often do not consider CF in the differential diagnosis of an infant with failure to thrive in the presence of a negative newborn screening (NBS) result. In Minnesota, newborn infants are screened for CF by immunoreactive trypsinogen (IRT) testing followed by DNA analysis if the IRT screen result is abnormal. All positive NBS results are followed by confirmatory sweat-testing by pilocarpine iontophoresis. We present here the case of a 1-month-old white boy with failure to thrive, chronic diarrhea, and severe malnutrition. Minnesota state CF NBS results were negative at birth (IRT: 43 ng/mL [96% cutoff value: 52 ng/mL]). Clinical symptoms resulted in sweat-testing by Gibson-Cooke pilocarpine iontophoresis at 1 month of age, and the result was positive (102 mmol Cl(-)/L [normal: ≤30 mmol Cl(-)/L]). CFTR mutation analysis confirmed a homozygous f508del genotype, and stool pancreatic elastase testing revealed severe exocrine pancreatic insufficiency. This case represents the first known false-negative result in Minnesota since the initiation of NBS for CF in 2006, which illustrates the importance of considering CF in the evaluation of an infant with failure to thrive and symptoms of malabsorption, regardless of NBS results.     

Recent advances in cystic fibrosis

The median life expectancy for cystic fibrosis is now over 30 years, and it is projected that in newborn infants it will become more than 40 years. The identification of the cystic fibrosis gene and its product, cystic fibrosis transmembrane conductance regulator (CFTR), has widened the spectrum of the disease from the classical case of the infant with cystic fibrosis to the elderly childless man with unexplained bronchiectasis. There is increasing evidence of the advantages of newborn screening for cystic fibrosis and subsequent specialist care. Management concentrates on optimising nutritional status and preventing lung infection and inflammation.     

Mutation analysis in the diagnosis of cystic fibrosis

Since the characterization of the gene encoding the cystic fibrosis transmembrane conductance regulator protein and identification of its main mutation, F508, causing cystic fibrosis (CF), more than 150 mutations in this gene have been reported, most of them only in a few or even single CF patients. Attempts to use mutation analysis in genetic counselling or for the diagnosis of CF depends on prevalence data of certain mutations in the respective population, and considerable ethnic differences have been reported. In this study we determined the prevalence of the mutations F508, G551D, R553X, and G542X and of genotypes defined by these mutations in 239 CF patients (444 independent CF chromosomes) seen in our clinic. The analysis for those four mutations alone now permits identification of approximately 75% of all mutations in our CF patients. The complete genotype can be resolved in approximately 63% of patients. This represents the diagnostic sensitivity which can be achieved by mutation analysis in patients without a family history of CF. We conclude that in situations where conventional diagnostic tests are not feasible or difficult to interpret, mutation analysis using a limited set of mutations can contribute significantly to an early and specific diagnosis of CF.     

Clinical and genetic risk factors for cystic fibrosis-related liver disease

OBJECTIVE: The aim of this study was to define the role of possible risk factors for the development of cystic fibrosis (CF)-related liver disease and to analyze the association between liver disease and the different genotypes present in the Israeli CF patient population. PATIENTS AND METHODS: All patients followed at the seven CF centers in Israel were included in this study. Liver disease was determined by persistently elevated serum liver enzymes and/or bilirubin, and/or significant ultrasonographic changes suggestive of chronic liver disease. The following clinical parameters were evaluated: ethnic origin, age at assessment of liver function, sex, history of meconium ileus, pancreatic function, history of distal intestinal obstruction syndrome, pulmonary function, and cystic fibrosis transmembrane conductance regulator mutation analysis. RESULTS: Of the 288 patients screened, 80 (28%) had liver disease. Of the 256 patients with pancreatic insufficiency, 80 (31%) had liver disease compared with none of the 32 patients with pancreatic sufficiency. Genotype-phenotype correlation was performed on 207 patients carrying identified mutations that were previously classified according to phenotype severity. Liver disease was found in 56 (32%) of 173 patients carrying mutations associated with a severe phenotype and in 6 (38%) of 16 patients carrying at least one mutation associated with a variable genotype (G85E and/or 5T allele). None of the 18 patients carrying the 3849+10kb C->T mutation had liver disease. Prevalence of liver disease increased with age. No correlation was found between liver disease and severity of lung disease, nutritional status, history of meconium ileus, or distal intestinal obstruction syndrome. CONCLUSION: CF patients who have pancreatic insufficiency and carry mutations associated with a severe or a variable genotype are at increased risk to develop liver disease.     

Heterogeneity of the cystic fibrosis phenotype in a large kindred family in Qatar with cystic fibrosis mutation (I1234V)

Twenty-nine subjects (17 families) with cystic fibrosis belonging to the same Bedouin tribe were screened for cystic fibrosis transmembrane regulator gene mutations (CFTR). Homozygous I1234V mutation in exon 19 was identified in all families with a relatively high rate of consanguinity (96.6 per cent). The homozygous I1234V mutation tended to present with a variable degree of pulmonary disease, pancreatic insufficiency and electrolyte imbalance. Homozygous I1234V was found to be a common mutation in the studied Bedouin tribe in Qatar.     

Recent advances in cystic fibrosis.

The median life expectancy for cystic fibrosis is now over 30 years, and it is projected that in newborn infants it will become more than 40 years. The identification of the cystic fibrosis gene and its product, cystic fibrosis transmembrane conductance regulator (CFTR), has widened the spectrum of the disease from the classical case of the infant with cystic fibrosis to the elderly childless man with unexplained bronchiectasis. There is increasing evidence of the advantages of newborn screening for cystic fibrosis and subsequent specialist care. Management concentrates on optimising nutritional status and preventing lung infection and inflammation.     

Role of <Emphasis Type="Italic">CFTR</Emphasis> mutation analysis in the diagnostic algorithm for cystic fibrosis

Background:The cystic fibrosis transmembrane conductance regulator (CFTR) gene mutation identification is being used with increased frequency to aid in the diagnosis of cystic fibrosis (CF) in those suspected with CF.Aim of this study was to identify diagnostic outcomes when CFTR mutational analysis was used in CF diagnosis.CFTR mutational analysis results were also compared with sweat chloride results.Methods:This study was done on all patients at our institution who had CFTR mutation analysis over a sevenyear period since August 2006.Results:A total of 315 patients underwent CFTR mutational analysis.Fifty-one (16.2％) patients had two mutations identified.Among them 32 had positive sweat chloride levels (≥60 mmol/L),while seven had borderline sweat chloride levels (40-59 mmol/L).An additional 70 patients (22.3％) had only one mutation identified.Among them eight had positive sweat chloride levels,and 17 had borderline sweat chloride levels.Fifty-five patients (17.5％) without CFTR mutations had either borderline (n=45) or positive (n=10) sweat chloride results.Three patients with a CF phenotype had negative CFTR analysis but elevated sweat chloride levels.In eighty-three patients (26.4％) CFTR mutational analysis was done without corresponding sweat chloride testing.Conclusions:Although CFTR mutation analysis has improved the diagnostic capability for CF,its use either as the first step or the only test to diagnose CFTR dysfunction should be discouraged and CF diagnostic guidelines need to be followed.     

Changing paradigms in the treatment of gastrointestinal complications of cystic fibrosis in the era of cystic fibrosis transmembrane conductance regulator modulators

Cystic fibrosis (CF) – although primarily a lung disease – also causes a variety of gastrointestinal manifestations which are important for diagnosis, prognosis and quality of life. All parts of the gastrointestinal tract can be affected by CF. Besides the well-known pancreatic insufficiency, gastroesophageal reflux disease, liver disease and diseases of the large intestine are important pathologies that impact on prognosis and also impair quality of life. Diagnosis and management of gastrointestinal manifestations will be discussed in this review. Since optimisation of CF therapy is associated with a significantly longer life-span of CF patients nowadays, also gastrointestinal malignancies, which are more common in CF than in the non-CF population need to be considered. Furthermore, novel evidence on the role of the gut microbiome in CF is emerging. The introduction of cystic fibrosis transmembrane conductance regulator (CFTR) protein modulators gives hope for symptom alleviation and even cure of gastrointestinal manifestations of CF.