Sweat Chloride Concentration Research Articles

O0101 CYSTIC FIBROSIS TRANSMEMBRANE CONDUCTANCE REGULATOR (CFTR) RELATED RECURRENT PANCREATITIS IN CHILDREN

Introduction: CFTR is expressed in the apical membrane of pancreatic duct epithelial cells and functions as a cAMP-regulated chloride channel. An association between CFTR gene mutations and pancreatitis has been reported. The aim of this prospective study was to look for CFTR gene mutations in patients with pancreatitis of unknown etiology. Methods: Patients and Methods: During the past 5 years (1998–2003), patients with abdominal pain and three-fold increased serum amylase were fully investigated. Each first acute pancreatitis episode of undetermined cause was further investigated with sweat chloride and fecal pancreatic elastase determinations and CFTR gene mutation analysis. Results: Results: In 14 (15% of total number of investigated patients), the cause of pancreatitis remained unknown. CFTR gene mutations were detected in 9/14 patients (3 boys and 6 girls), aged 6 to 15 (mean 12) years. CFTR mutations, sweat chloride concentrations and fecal pancreatic elastase values are shown in the table. The diagnosis of cystic fibrosis was documented. in 7 CFTR mutation positive patients having abnormal sweat tests. Two CFTR- positive siblings had normal sweat chloride concentrations. All 9 patients had a total number of 32 episodes of pancreatitis (2–9, mean 4 per year) in five 5 years. During this period, abdominal sonography findings were non-specific and pseudocysts were not detected. Pancreatic function remained normal.Table 1Conclusion: Conclusions: Our data adds further information on the relation of CFTR mutations and recurrent pancreatitis in children. CFTR related pancreatitis may be the presenting manifestation of cystic fibrosis. Children with pancreatitis of undetermined cause should be screened for mutations in the CFTR gene.

P1151 DIETARY INTAKES AND PLASMA POLYUNSATURATED FATTY ACIDS IN CHILDREN WITH CYSTIC FIBROSIS: A DIFFICULT BALANCE.

Introduction: Poor clinical outcomes are associated with undernutrition in patients with cystic fibrosis (CF). Thus, a consumption of 120–150% the recommended dietary allowances for energy is suggested. A poor polyunsaturated fatty acid (PUFA) status may further contribute to the clinical course of CF. Methods: Forty-six patients with CF (19 males), diagnosed on the basis of typical symptoms, increased sweat chloride concentrations on at least two occasions and genotype analysis, mean age 7.8, SD 2.6, yrs, were compared with a reference group of sixty-nine 8-yrs old healthy children as far as dietary intakes (all CF) and fatty acid status (18 CF). CF patients received high-calorie extra-meals (mainly dairy products) and/or oral supplements with protein/fat/carbohydrate mixtures. Overall they were in good nutritional status (mean z score for weight: −0.301, SD 1.223; mean z score for height: −0.265, SD 0.946). Most of them (39) were under pancreatic enzyme supplementation. Dietary habits were investigated by means of a validated food-frequency questionnaire. Plasma fatty acids, extracted according to Folch, were determined by means of capillary gas-chromatography. Statistics: parametric and non-parametric tests, when appropriate. Statistical significance: P <0.05 for all the reported differences and correlations. Results: CF patients showed higher energy intakes than controls (2606, SD 808, vs 2003, SD 422, kcal/day). Considering percentages of macronutrient intakes, CF children showed higher levels of total (saturated and monounsaturated) fats and lower levels of carbohydrates. Percentage intakes of PUFA were comparable in the two groups. CF patients showed higher plasma concentrations of saturated and monounsaturated FA and lower PUFA levels (32, SD 5, vs 40, SD 3, %). Among PUFA, both linoleic and docosahexaenoic acids were lower in CF patients (21, SD 4, vs 27, SD 3, and 0.9, SD 0.3, vs 1.7, SD 0.9, %, respectively). Energy intakes in CF were inversely related to plasma total PUFA, linoleic and docosahexaenoic acids. Conclusion: Increasing by means of presently available supplements total energy intakes in CF patients does not match a parallel increase of dietary PUFA. CF patients show lower PUFA levels in plasma lipids than healthy controls, in spite of a higher energy supply. Since increased energy intakes are negatively associated with plasma PUFA levels, our data suggest the need of specific PUFA supplementations for children with CF.

A Finger Sweat Chloride Test for the Detection of a High-Risk Group of Chronic Pancreatitis

Mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene are associated with chronic pancreatitis in Caucasians. We developed a simple method for measuring finger sweat chloride concentration to test whether CFTR dysfunction underlies chronic pancreatitis in Japan where cystic fibrosis (CF) is rare. We studied 25 patients with chronic (21 alcoholic and 4 idiopathic) pancreatitis and 25 healthy volunteers. Sweat chloride concentrations were measured by a finger sweat chloride test. We analyzed DNA for 20 common CFTR mutations in Europeans, 9 CF-causing mutations in Japanese, and 2 polymorphic loci, a poly-T tract and (TG) repeats, at intron 8. Thirteen patients (52%) had sweat chloride levels >60 mmol/L, a level consistent with CF, while only 4 (16%) healthy subjects exceeded this level. The 29 CF mutations and the 5T allele were detected in neither the patients nor controls. The (TG) 12 allele was common in both the patients (58%) and controls (48%). The (TG) 12/12 genotype was common in alcoholic pancreatitis (29%) compared with the (TG) 11/11 (10%). Patients with the (TG) 12/12 genotype had significantly higher sweat chloride concentrations than the controls. CFTR dysfunction as evidenced by a finger sweat chloride test is present in about half of Japanese patients with chronic pancreatitis, suggesting that this test may be useful for detecting the high-risk group. A higher proportion of the (TG) 12 allele may be a genetic background for elevated sweat chloride concentrations in Japanese patients.

Newborn screening for cystic fibrosis: ensuring more good than harm

Newborn screening for cystic fibrosis: ensuring more good than harm

CFTR genotypes in patients with normal or borderline sweat chloride levels.

In recent years, some patients bearing "atypical" forms of cystic fibrosis (CF) with normal sweat chloride concentrations have been described. To identify the spectrum of mutant combinations causing such atypical CF, we collected the results of CFTR (ABCC7) mutation analysis from 15 laboratories. Thirty patients with one or more typical symptoms of the disease associated with normal or borderline sweat chloride levels and bearing two CFTR mutations were selected. Phenotypes and genotypes of these 30 patients are described. A total of 18 different CFTR mutations were observed in the 60 chromosomes analysed. F508del was present in 31.6 % of the mutated chromosomes and 3849+10kbC>T in 13.3 %. R117H, D1152H, L206W, 3272-26A>G, S1235R, G149R, R1070W, S945L, and the poly-T tract variation commonly called IVS8-5T were also observed. The relative frequency of CFTR mutations clearly differed from that observed in typical CF patients or in CBAVD patients with the same ethnic origin. A mild genotype with one or two mild or variable mutations was observed in all the patients. These findings improve our understanding of the distribution of CFTR alleles in CF with normal or borderline sweat chloride concentrations and will facilitate the development of more sensitive CFTR mutation screening.

Variant cystic fibrosis phenotypes in the absence of CFTR mutations.

Cystic fibrosis is a life-limiting autosomal recessive disorder with a highly variable clinical presentation. The classic form involves characteristic findings in the respiratory tract, gastrointestinal tract, male reproductive tract, and sweat glands and is caused by loss-of-function mutations in the cystic fibrosis transmembrane conductance regulator (CFTR ) gene. Nonclassic forms of cystic fibrosis have been associated with mutations that reduce but do not eliminate the function of the CFTR protein. We assessed whether alteration in CFTR function is responsible for the entire spectrum of variant cystic fibrosis phenotypes. Extensive genetic analysis of the CFTR gene was performed in 74 patients with nonclassic cystic fibrosis who had been referred by 34 medical centers. We evaluated two families that each included a proband without identified mutations and a sibling with nonclassic cystic fibrosis to determine whether there was linkage to the CFTR locus and to measure the extent of CFTR function in the sweat gland and nasal epithelium. Of the 74 patients studied, 29 had two mutations in the CFTR gene, 15 had one mutation, and 30 had no mutations. A final genotype of two mutations was more common among patients who had been referred after screening for common cystic fibrosis-causing mutations identified one mutation than among those who had been referred after screening had identified no such mutations (26 of 34 patients vs. 3 of 40 patients, P<0.001). Comparison of clinical features and sweat chloride concentrations revealed no significant differences among patients with two, one, or no CFTR mutations. Haplotype analysis in the two families revealed no linkage to CFTR. Although each of the affected siblings had elevated sweat chloride concentrations, measurements of cyclic AMP-mediated ion and fluid transport in the sweat gland and nasal epithelium demonstrated the presence of functional CFTR. Factors other than mutations in the CFTR gene can produce phenotypes clinically indistinguishable from nonclassic cystic fibrosis caused by CFTR dysfunction.

Mutations of the cystic fibrosis gene and intermediate sweat chloride levels in children.

The incidence of mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene in children with intermediate sweat chloride levels is unknown. The results of 2,349 sweat tests performed at two Belgian university hospitals were reviewed. Intermediate chloride concentrations were observed in 98 subjects (4.2%), 68 being younger than 18 years of age. Forty-three children could be traced and their parents agreed to take part in the study. Exhaustive analysis of the CFTR gene disclosed a total of 24 putative mutations (27.9%). Three subjects were found to carry only one CFTR mutation, whereas 10 harbored one mutation on both CFTR genes. These 10 children were investigated in detail. At the time of writing, the mean age (+/-SD) of this group is 8.9 years (+/-4.2 years). Nine children are pancreatic sufficient. Three have been asymptomatic for more than two years, whereas the others display, to different degrees, clinical features suggestive of CF. The sweat chloride concentration is slightly higher in this group (39.4 +/- 5.4 mM) than in subjects without CFTR mutation (35.2 +/- 4.4 mM, p < 0.05). The nasal potential difference was abnormal in five of the nine subjects tested. In this study, 23% of children displaying intermediate sweat chloride levels were found to carry a putative mutation on both CFTR genes.

The pancreas in cystic fibrosis.

The pancreas secretes a bicarbonate-rich fluid containing digestive enzymes via the ampulla of Vater into the duodenum. Defective secretion leads to maldigestion of fat and protein with increased faecal losses. Cystic fibrosis (CF) is the major cause of pancreatic exocrine failure in childhood, whereas pancreatic insufficiency in adults is commonly associated with chronic pancreatitis and alcohol ingestion. In cystic fibrosis, pancreatic function correlates with genotype; pancreatic-sufficient (PS) patients have a milder course of respiratory disease, improved survival and lower mean sweat chloride concentrations than those with pancreatic insufficiency. Recent observations suggest that mutant CF alleles are over-represented in patients with chronic pancreatitis. Few show evidence of sino-pulmonary disease or high sweat electrolyte concentrations.

Advances in the diagnosis of cystic fibrosis in infants

Advances in the diagnosis of cystic fibrosis in infants

High morbidity and mortality in cystic fibrosis patients compound heterozygous for 3905insT and deltaF508.

Genotype-phenotype association in cystic fibrosis (CF) is difficult because of heterogeneous disease expression. The genotype-phenotype correlation for the 3905insT mutation in comparison to deltaF508 was studied here. Thirty CF patients compound heterozygous for 3905insT were compared to clinical presentation of matched patients homozygous for deltaF508 (1960-1997). Sweat tests, age at diagnosis, at death and at onset of Pseudomonas aeruginosa colonization were analysed. Chrispin-Norman scores and pulmonary function forced expiratory volume in one second (FEV1) determined severity of lung disease. Twenty-five of the patients with 3905insT had deltaF508 as a second mutation and five had another rare mutation. At the age of 15 yrs, 60% of patients with 3905insT had an FEV1 < 60% predicted in comparison to 25% of patients with deltaF508 (p<0.05). Age at death and cumulative survival rate was significantly lower (p<0.05) in the 3905insT than in the deltaF508 group (20.3 and 24.0 yrs, respectively). Age at onset of P. aeruginosa colonization was not different in the study groups. Sweat chloride concentrations were lower in patients homozygous for deltaF508 (105.63+/-15.3 mmol L(-1)) than in patients with 3905insT (119.9+/-22.1 mmol x L(-1)) (p<0.05). Patients compound heterozygous for 3905insT have similar high morbidity and mortality to patients homozygous for deltaF508.

Nasal potential difference measurements in patients with atypical cystic fibrosis.

The diagnosis of cystic fibrosis (CF) is based on characteristic clinical and laboratory findings. However, a subgroup of patients present with an atypical phenotype that comprises partial CF phenotype, borderline sweat tests and one or even no common cystic fibrosis transmembrane conductance regulator (CFTR) mutations. The aim of this study was to evaluate the role of nasal potential difference (PD) measurements in the diagnosis of CF patients with an atypical presentation and in a population of patients suspected to have CF. Nasal PD was measured in 162 patients from four different groups: patients with classical CF (n = 31), atypical phenotype (n = 11), controls (n = 50), and patients with questionable CF (n = 70). The parameter, or combination of nasal PD parameters was calculated in order to best discriminate all CF patients (including atypical CF) from the non-CF group. The patients with atypical CF disease had intermediate values of PD measurements between the CF and non-CF groups. The best discriminate model that assigned all atypical CF patients as CF used: e(response to chloride-free and isoproterenol/response to amiloride) with a cut-off >0.70 to predict a CF diagnosis. When this model was applied to the group of 70 patients with questionable CF, 24 patients had abnormal PD similar to the atypical CF group. These patients had higher levels of sweat chloride concentration and increased rate of CFTR mutations. Nasal potential difference is useful in diagnosis of patients with atypical cystic fibrosis. Taking into account both the sodium and chloride transport elements of the potential difference allows for better differentiation between atypical cystic fibrosis and noncystic fibrosis patients. This calculation may assist in the diagnostic work-up of patients whose diagnosis is questionable.

Frequency of Cystic Fibrosis Transmembrane Conductance Regulator Gene Mutations and 5T Allele in Patients With Allergic Bronchopulmonary Aspergillosis

To assess the frequency of cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations in patients with allergic bronchopulmonary aspergillosis (ABPA). Case-control study. All subjects in the study were screened for the presence of 13 mutations in the CFTR gene (R117H, 621 + 1G(-)>T, R334 W, Delta F508, Delta I507, 1717-1G(-)>A, G542X, R553X, G551D, R1162X, 3849 + 10kbC(-)>T, W1282X, and N1303K). Moreover, they were also screened for the presence of the 5T variant in intron 8. University hospital and community-based hospital. Twenty-one white patients with ABPA participated in the study. The presence of CFTR mutations was also investigated in 43 white subjects with allergic asthma who did not show sensitization to Aspergillus fumigatus and in 142 subjects seeking genetic counseling for diseases other than cystic fibrosis (CF). Six patients with ABPA were found to be heterozygous for one CFTR mutation, including Delta F508 (n = 2), G542X (n = 1), R1162X (n = 1), 1717-1G(-)>A (n = 1), and R117H (n = 1). The 5T allele was not detected in ABPA patients. None of the ABPA patients showed sweat chloride concentrations > 60 mEq/L. The frequency of CFTR mutation carriers was significantly higher in ABPA patients (6 of 21 patients; 28.5%) than in control asthmatic subjects (2 of 43 subjects; 4.6%; p = 0.01) and in subjects seeking genetic counseling (6 of 142 subjects; p < 0.001). These findings indicate that in patients without a clinical diagnosis of CF, CFTR gene mutations could be involved in the development of ABPA, in association with other genetic or environmental factors.

Protracted neonatal hypertrypsinogenaemia, normal sweat chloride, and cystic fibrosis

The cystic fibrosis (CF) clinical spectrum has greatly expanded in the past few years, including atypical forms with low sweat chloride concentrations. Two cases are presented which suggest that children...

GENOTYPE-PHENOTYPE RELATIONSHIPS IN CYSTIC FIBROSIS

The genotype-phenotype relationship in CF is complex despite its being a monogenic disorder. Factors that contribute to variability among individuals with the same genotype are an area of intense study. Nevertheless, certain conclusions can be derived from these studies. First, mutations in both CFTR alleles cause the CF phenotype. Homozygosity for delta F508 or compound heterozygosity for delta F508 and another severe mutation (e.g., G551D, W1282X) cause classic CF: obstructive pulmonary disease, exocrine pancreatic deficiency, male infertility, and elevated sweat chloride concentrations. Clinical variability is observed among patients with the classic form of CF, especially with regards to the severity of lung disease. Although understanding of the role of other genes and environment in the development of lung disease is incomplete, evidence that other factors are important raises the possibility that therapeutic intervention may be possible at several levels. Second, genotype correlates more closely with certain features of the CF phenotype than others. Mutations that allow partial function of CFTR are often associated with pancreatic sufficiency, occasionally identified with normal sweat gland function, and sporadically correlated with mild lung disease. Partially functioning mutants rarely prevent maldevelopment of the male reproductive tract; an exception is 3849 + 10 Kb C-->T. These observations suggest that certain tissues require different levels of CFTR function to avoid the pathologic manifestations typical of CF. The genetic cause of several disorders that clinically overlap CF can be attributed, in part, to mutations in CFTR. Finally, molecular analysis of disease-associated mutations identified through genotype-phenotype studies provides a mechanistic framework for genotype-based therapeutic approaches and pharmaceutical interventions.

Serum lipase levels as a diagnostic marker in cystic fibrosis patients with normal or borderline sweat tests.

Patients with normal or borderline sweat test present a diagnostic challenge. In spite of the availability of different methods such as genetic analysis and measurements of nasal potential difference, uncertainty in diagnosing cystic fibrosis (CF) in some patients still exists. Neonates with CF have high serum lipase levels, which decline over time in pancreatic-insufficient patients, whereas pancreatic-sufficient patients demonstrate high serum lipase levels beyond infancy. Because patients with borderline or normal sweat test are almost always pancreatic sufficient, this study was aimed to assess whether serum lipase levels may be of help in establishing the diagnosis of CF in these patients. Serum lipase levels were measured in 100 CF patients and in 17 healthy individuals. Patients were grouped according to their genotype. Group A patients (n = 70) carried two mutations previously found to be associated with a pathologic sweat test and pancreatic insufficiency (delta F508, W1282X, G542X, N1303K, S549R). Group B (n = 30) were compound heterozygote patients who carried one mutation known to cause mild disease with borderline or normal sweat tests and pancreatic sufficiency (3849+10kb C-->T, 5T). Group C included 17 healthy controls. Serum lipase levels ranged between 2 and 104.4 U/L (mean +/- SD 16.9 +/- 14.7), 6.1-200 U/L (mean +/- SD 53.9 +/- 47.9), and 8.5-27.8 U/L (mean +/- SD 16.9 +/- 5.1) in Groups A, B, and C, respectively, with some overlapping between groups. The distribution of lipase levels was significantly different in Group B vs Groups A and C (P < 0.01). High lipase levels were found in 63.3% (19/30) of Group B patients, but in only 4.3% (3/70) and 0% (0/17) of Group A and C, respectively. Lipase levels were found to be inversely related to sweat chloride concentrations (r = -0.19, P < 0.05). Patients with borderline or normal sweat tests had high lipase levels, whereas low lipase levels were associated with pathologic sweat tests. Our findings indicate that the serum lipase level is genetically determined and that it has a useful role in the diagnosis of CF. Thus, in patients with borderline sweat tests and high lipase levels, the diagnosis of CF should be considered.

Genotype-phenotype correlations in cystic fibrosis: clinical severity of mutation S549R(T-->G).

With a view to assessing genotype-to-phenotype correlations in cystic fibrosis (CF), the clinical presentation of CF children from the United Arab Emirates (UAE) who were homozygous for cystic fibrosis transmembrane conductance regulator (CFTR) mutation S549R(T-->G was investigated. This mutation is localized in intron 11 (nucleotide binding domain 1 of the CFTR protein) and had so far been described as a private mutation only. The associations between the R549/R549 genotype and 20 outcome variables, including age at diagnosis, sweat chloride concentrations, growth percentiles, meconium ileus, pancreatic sufficiency, pulmonary disease, associated complications and micro-organism colonization were examined in a group of 15 CF children (9 females and 6 males). Mean current age and age at diagnosis were both low (5.4+/-3.5 and 1.0+/-1.1 yrs, respectively). Although none of the 15 CF patients had presented with meconium ileus at birth, all were pancreatic insufficient and had very severe lung disease, with a high rate of Pseudomonas aeruginosa and Staphylococcus aureus. Two patients died during the course of this investigation (one was 5 months and the other, 6 yrs old). The clinical presentation associated with S549R(T-->G) homozygosity in the United Arab Emirates is quite homogeneous and shows an extreme degree and course of cystic fibrosis severity.

Increased Sweat Chloride Concentrations in Adult Patients with Pancreatic Insufficiency: Cystic Fibrosis Phenotype or Lack of Specificity of Sweat Test?

Increased Sweat Chloride Concentrations in Adult Patients with Pancreatic Insufficiency: Cystic Fibrosis Phenotype or Lack of Specificity of Sweat Test?

Test for the Concentration of Electrolytes in Cystic Fibrosis of the Pancreas Utilizing Pilocarpine by Iontophoresis, by Lewis E. Gibson and Robert E. Cooke,Pediatrics; 1959;24:545–549

Aim. To develop a method for stimulating sweating that is rapid, painless, and avoids the risk of heat stress.Background. Since the discovery that there is a high concentration of sodium and chloride in the sweat of patients with cystic fibrosis of the pancreas in 1953, the sweat test has been performed by placing the patient's body in a plastic bag with or without hot water bottles to stimulate sweating. This method is unsatisfactory because of complications such as hyperpyrexia and heat stroke. Direct injection of a cholinergic agent intradermally is painful and therefore not practical.Methods. A rheostat with a milliampere meter was constructed at a cost of ∼$7 that allowed the iontophoresis of pilocarpine into the skin using negative and positive (2-cm diameter) electrocardiography electrodes. The positive electrode was placed on the flexor surface of the arm over a filter paper soaked in 0.2 mL of 0.2% pilocarpine nitrate. Current (0.2 mA) was applied for 5 minutes and then sweat was collected onto a preweighed filter paper for 30 minutes. Sweat chloride was determined by a polarographic method. Sweat tests were performed on 25 patients with cystic fibrosis (CF), 17 asymptomatic relatives and 27 control patients. Patients with CF had sweat chloride concentration &amp;gt;80 mEq/L; relatives, 32.5 mEq/L (highest 57 mEq/L); and control subjects, 21.1 mEq/L (highest 60 mEq/L).Conclusions. The iontophoresis of pilocarpine into the skin is a rapid, painless, safe, and reliable method for stimulating sweating and facilitating the determination of sweat chloride concentration.

A mutation in the cystic fibrosis transmembrane conductance regulator gene associated with elevated sweat chloride concentrations in the absence of cystic fibrosis.

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) have been shown to cause cystic fibrosis (CF) and male infertility due to congenital bilateral absence of the vas deferens. We report the identification of a 6.8 kb deletion (del14a) and a nonsense mutation (S1455X) in the CFTR genes of a mother and her youngest daughter with isolated elevated sweat chloride concentrations. Detailed clinical evaluation of both individuals found no evidence of pulmonary or pancreatic disease characteristic of CF. A second child in this family with classic CF was homozygous for the del14a mutation, indicating that this mutation caused severe CFTR dysfunction. CFTR mRNA transcripts bearing the S1455X mutation were stable in vivo , implying that this allele encoded a truncated version of CFTR missing the last 26 amino acids. Loss of this region did not affect processing of transiently expressed S1455X-CFTR compared with wild-type CFTR. When expressed in CF airway cells, this mutant generated cAMP-activated whole-cell chloride currents similar to wild-type CFTR. Preservation of chloride channel function of S1455X-CFTR was consistent with normal lung and pancreatic function in the mother and her daughter. These data indicate that mutations in CFTR can be associated with elevated sweat chloride concentrations in the absence of the CF phenotype, and suggest a previously unrecognized functional role in the sweat gland for the C-terminus of CFTR.

P67L: a cystic fibrosis allele with mild effects found at high frequency in the Scottish population.

Only three mutant cystic fibrosis (CF) alleles have to date been established as conferring a dominant mild effect on affected subjects who are compound heterozygotes. We now add a fourth,...