Meconium ileus equivalent in adults with cystic fibrosis of pancreas: a report of six cases.

Eleven episodes of "meconium ileus equivalent" have been seen in six adults with cystic fibrosis of the pancreas. Three patients were initially treated surgically; one died and the other two developed serious postoperative chest infections. Six episodes were successfully treated medically with acetylcysteine orally and by enema, nasogastric suction, and intravenous fluids. Operation should be avoided if possible, and maintenance treatment with acetylcysteine may be necessary to prevent relapse.     

Prenatal diagnosis in 200 pregnancies with a 1-in-4 risk of cystic fibrosis

Summary Prenatal diagnosis of cystic fibrosis was performed in 200 pregnancies with a 1-in-4 risk, and was based on significant modifications in amniotic fluid taken at 17, 18, 19 weeks of pregnancy, of six enzymatic assays: gamma-glutamyl-transpeptidase, aminopeptidase M, and alkaline phosphatase (total and isoenzymes). On the basis of normal values, normal outcome was predicted in 135 pregnancies reaching term, all the babies were normal. On the basis of significantly abnormal enzymatic values, an affected fetus was predicted in 56 pregnancies, 53 were terminated, and 3 went to term; the infants were affected. There were discrepancies in enzymatic values in nine cases, in eight cases normal outcome was predicted, six babies were normal and two were affected; in one case an affected baby was predicted, the pregnancy went to term and the baby is normal. Criteria giving evidence for cystic fibrosis in fetuses have been described: macroscopic observation of a typical meconium ileus, significant increase of albumin content in the meconium, and PAS-positive mucus-like material in some pancreatic acini. Using these criteria, diagnosis of cystic fibrosis has been confirmed in all the examined fetuses. The recurrence rate of cystic fibrosis was 22.5% in 147 diagnoses in which the index case had cystic fibrosis without a history of meconium ileus at birth, but was 47.5% when the index case had meconium ileus. The results of the study suggest that prenatal diagnosis of cystic fibrosis can be performed with an accuracy of 98%.     

Neonatal screening for cystic fibrosis using immunoreactive trypsinogen and direct gene analysis: four years' experience.

OBJECTIVE--To assess the performance and impact of a two tier neonatal screening programme for cystic fibrosis based on an initial estimation of immunoreactive trypsinogen followed by direct gene analysis. DESIGN--Four year prospective study of two tier screening strategy. First tier: immunoreactive trypsinogen measured in dried blood spot samples from neonates aged 3-5 days. Second tier: direct gene analysis of cystic fibrosis mutations (delta F508, delta I506, G551D, G542X, and R553X) in samples with immunoreactive trypsinogen concentrations in highest 1% and in all neonates with meconium ileus or family history of cystic fibrosis. SETTING--South Australian Neonatal Screening Programme, Adelaide. SUBJECTS--All 88,752 neonates born in South Australia between December 1989 and December 1993. INTERVENTIONS--Neonates with two identifiable mutations were referred directly for clinical assessment and confirmatory sweat test; infants with only one identifiable mutation were recalled for sweat test at age 3-4 weeks. Parents of neonates identified as carriers of cystic fibrosis mutation were counselled and offered genetic testing. MAIN OUTCOME MEASURES--Identification of all children with cystic fibrosis in the screened population. RESULTS--Of 1004 (1.13%) neonates with immunoreactive trypsinogen > or = 99th centile, 912 (90.8%) had no identifiable mutation. 23 neonates were homozygotes or compound heterozygotes; 69 carried one identifiable mutation, of whom six had positive sweat tests. Median age at clinical assessment for the 29 neonates with cystic fibrosis was 3 weeks; six had meconium ileus and two had affected siblings. 63 neonates were identified as carriers of a cystic fibrosis mutation. Extra laboratory costs for measuring immunoreactive trypsinogen and direct gene analysis were $A1.50 per neonate screened. CONCLUSION--This strategy results in early and accurate diagnosis of cystic fibrosis and performs better than screening strategies based on immunoreactive trypsinogen measurement alone.     

Cystic fibrosis mice carrying the missense mutation G551D replicate human genotype-phenotype correlations.

We have generated a mouse carrying the human G551D mutation in the cystic fibrosis transmembrane conductance regulator gene (CFTR) by a one-step gene targeting procedure. These mutant mice show cystic fibrosis pathology but have a reduced risk of fatal intestinal blockage compared with 'null' mutants, in keeping with the reduced incidence of meconium ileus in G551D patients. The G551D mutant mice show greatly reduced CFTR-related chloride transport, displaying activity intermediate between that of cftr(mlUNC) replacement ('null') and cftr(mlHGU) insertional (residual activity) mutants and equivalent to approximately 4% of wild-type CFTR activity. The long-term survival of these animals should provide an excellent model with which to study cystic fibrosis, and they illustrate the value of mouse models carrying relevant mutations for examining genotype-phenotype correlations.     

Molecular bases for cystic fibrosis in the Sardinian population

Summary Cystic fibrosis (CF) is a relatively uncommon genetic disorder in the Sardinian population. In this study, we have defined the frequency of the most common CF mutation (ΔF508) and carried out a genotypephenotype correlation analysis in a group of 21 patients with CF and of Sardinian descent. We detected the ΔF508 mutation in 24 (57%) out of the 42 CF chromosome investigated. This mutation was found in the homozygous state in 9 patients and in the heterozygous state in 6 patients. The remaining 6 patients had other mutations. The ΔF508 mutation was associated only with the KM19/XV2c 2 1 haplotype. Genotype-phenotype correlation analysis did not give clear-cut results, probably because of the small number of patients investigated. However, out of the four patients with meconium ileus, three were homozygous and one was heterozygous for the ΔF508 mutation, confirming that the presence of ΔF508 or other severe mutations in the homozygous state is the prerequisite for the development of meconium ileus.     

Cystic fibrosis haplotype association and the ΔF508 mutation in adult British CF patients

Summary The ΔF508 mutation and cystic fibrosis (CF) haplotypes with the markers KM19, pMP6d-9 and J3.11 are described in 54 adult British CF patients. ΔF508 was found on 70% of all CF chromosomes, on none of the normal chromosomes and on only 37.5% of pancreatic sufficient CF chromosomes. All patients with meconium ileus were homozygous for the deletion.     

The incidence of ΔF508 CF mutation,and associated haplotypes,in a sample of English CF families

Summary Data are presented for ΔF508 screening and KM19/XV2c haplotype analysis of 195 cystic fibrosis (CF) chromosomes from the British Caucasian population. We report the frequency of ΔF508 in this group to be 80% and find pronounced disequilibrium between the deletion and the KM 2, XV 1 haplotype. Haplotype analysis of 71 normal chromosomes is also presented. We report one individual who had meconium ileus and who does not have the ΔF508 mutation on either chromosome.     

Cystic fibrosis patients bearing both the common missense mutation, Gly→Asp at codon 551 and the ΔF508 mutation are clinically indistinguishable from ΔF508 homozygotes, except for decreased risk of meconium ileus

The glycine-to-aspartic acid missense mutation at codon 551 (G551D), which is within the first nucleotide-binding fold of the cystic fibrosis transmembrane conductance regulator (CFTR), is the third most common cystic fibrosis (CF) mutation, with a worldwide frequency of 3.1% among CF chromosomes. Regions with a high frequency correspond to areas with large populations of Celtic descent. To determine whether G551D confers a different phenotype than does delta F508, the most common CF mutation, we studied 79 compound heterozygotes for G551D/delta F508, from nine centers in Europe and North America. Each subject was matched, by age and sex, with a delta F508 homozygote from the same center. A retrospective cohort analysis was performed on the following outcome parameters: age at diagnosis, sweat chloride, meconium ileus at birth, height, weight, weight for height, FVC, FEV1, chest X-ray score, pseudomonas colonization, pancreatic sufficiency, and Shwachman clinical score. There was less meconium ileus among the G551D/delta F508 compound heterozygotes (relative risk 0.33; 95% confidence interval .13-.86), as well as a trend toward later age at diagnosis of pancreatic insufficiency. No statistically significant difference was found between the groups for any other parameter. These results suggest that the CF genotype can be a predictor of pancreatic and intestinal phenotype. Prenatal counseling for the two genotype groups should differ only with respect to probability of meconium ileus. Clinical outcome (after survival of meconium ileus) for G551D/delta F508 compound heterozygotes and delta F508 homozygotes is indistinguishable; therefore, prognostic counseling should not differ.     

Genetic comparisons of patients with cystic fibrosis with or without meconium ileus. Clinical Centers of the French CF Registry.

Cystic fibrosis (CF) is an autosomal disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator gene (CFTR). Neonatal meconium ileus (MI) occurs in 10-20 percent of newborns with CF. The purpose of this study was to determine the allelic frequencies of the CF mutation in French patients with and without MI and the incidence of MI in 7 homozygotes or compound heterozygotes for mutation of the CFTR gene. Our study confirms the positive association between delta F508, the most frequent CF mutation, G542X mutation and MI and a negative association with G551D.     

Association of a nonsense mutation (W1282X), the most common mutation in the Ashkenazi Jewish cystic fibrosis patients in Israel, with presentation of severe disease

Only about 30% of the cystic fibrosis chromosomes in the Israeli cystic fibrosis patient populations carry the major CF mutation (delta F508). Since different Jewish ethnic groups tended to live as closed isolates until recent times, high frequencies of specific mutations are expected among the remainder cystic fibrosis chromosomes of these ethnic groups. Genetic factors appear to influence the severity of the disease. It is therefore expected that different mutations will be associated with either severe or mild phenotype. Direct genomic sequencing of exons included in the two nucleotide-binding folds of the putative CFTR protein was performed on 119 Israeli cystic fibrosis patients from 97 families. One sequence alteration which is expected to create a termination at residue 1282 (W1282X) was found in 63 chromosomes. Of 95 chromosomes, 57 (60%) are of Ashkenazi origin. Together with the delta F508 (23% in this group), G542X, N1303K, and 1717-1G----A mutations, the identification of 92% of cystic fibrosis chromosomes of Ashkenazi origin becomes possible. Patients homozygous for the W1282X mutation (n = 16) and patients heterozygous for the delta F508 and W1282X mutations (n = 22) had similarly severe disease, reflected by pancreatic insufficiency, high incidence of meconium ileus (37% and 27%, respectively), early age at diagnosis, poor nutritional status, and variable pulmonary function. In conclusion, the W1282X mutation is the most common cystic fibrosis mutation in the Ashkenazi Jewish patient population in Israel. This nonsense mutation is associated with presentation of severe disease.     

HFE alleles in an Irish cystic fibrosis population

The variable clinical manifestations of cystic fibrosis (CF) suggest the influence of modifier genes. Genetic and environmental factors that determine whether an individual will develop associated complications are still being determined. It has been proposed that the gene for hemochromatosis, HFE, may be a modifier locus for CF disease phenotype. Recent research has suggested a relationship between mutations to the HFE gene and the development of meconium ileus (MI) and liver disease in CF. This study aims to expand our knowledge of the HFE mutations C282Y and H63D carrier rate in an Irish population of CF allele carriers. PCR restriction enzyme analysis was performed on blood samples from CF patients to identify the C282Y and H63D mutations. HFE status of CF allele carriers and CF patients (Delta F508) homozygotes with and without meconium ileus was determined. The carrier frequency for C282Y was 30.8% for the Delta F508 homozygote MI positive group, as compared to 12.5% for the non-Delta F508 MI positive group but did not reach statistical significance (p = 0.27). Interestingly, no Delta F508 homozygote patients were homozygous for the C282Y mutation.     

The Meconium-Plug Syndrome and Hirschsprung's Disease

A mass of inspissated meconium in the distal colon or rectum is a relatively common cause of neonatal intestinal obstruction. The meconium-plug syndrome is unrelated to cystic fibrosis and meconium ileus. The clinical picture is frequently indistinguishable, without contrast study of the colon, from other forms of mechanical intestinal obstruction requiring laparotomy. A barium enema examination is almost always diagnostic, and use of this procedure usually results in dislodgement and passage of the plug.No single cause for the excessive viscosity and tenaciousness of the obstructive meconium mass has been identified. Previous reports have generally emphasized the normal ganglion-cell content of the colon in affected patients.Two infants are described who fulfilled all criteria for this syndrome but who were not rendered asymptomatic, as normally anticipated, by removal of the plug. Subsequent studies revealed the presence of Hirschsprung''s disease in both patients. This diagnosis should be considered when an infant with meconium-plug obstruction of the colon fails to follow the usual satisfactory clinical course after the plug has been passed.     

Clinical and Diagnostic Significance of Enteroclysis Through Nasointestinal Decompression Intubation

To study the clinical and diagnostic significance of enteroclysis through nasointestinal decompression intubation, thirty-five patients with small bowel obstruction were enrolled. A nasointestinal catheter of 300 cm was placed through the nasal cavity then pushed to the upper jejunum under X-ray realtime monitoring. The patients underwent intra-small-intestinal suction therapy reducing or relieving the obstruction after 3 days. As the catheter reached the lesions, we conducted selective imaging. Using fluoroscopy, we injected 20–100 ml meglumine diatrizoate 76 % and 50–200 ml air via the decompression suction port to produce a double-contrast radiography. The catheter was then retrieved to the upper jejunum, and the X-ray of the small intestine was obtained. All 35 patients had successful intubations. The decompression treatment resolved symptoms in 20 cases and alleviated symptoms in 15 cases. Ten cases underwent surgery. The images obtained by infusing meglumine diatrizoate through the decompression catheter were of good quality. Among the 35 cases, six were absent of any distinct abnormal signs on the X-ray, 15 had adhesive ileus, four had small bowel tumor (three metastatic tumor, one small bowel cancer), three had Crohn’s disease, three had radiation enteritis (one of the three was mistaken for small bowel metastatic tumor), two had enteric intussusception, one had a polyp in the small intestine, one had ascending colon cancer. The nasointestinal decompression intubation under X-ray monitoring serves a dual function for patients with intestine obstruction, by decompressing the small bowel and examining the small intestinal radiographically. The X-rays can confirm the obstruction and provide guidelines for surgery.     

The cystic fibrosis ΔF508 mutation in the French population

Summary French families (n = 129) with at least one cystic fibrosis (CF) affected child and 44 unrelated subjects from the general population were tested for the presence of the ΔF508 mutation by the polymerase chain reaction. The ΔF508/CF mutation ratio (CF: uncharacterised CF mutations) was tested in the CF families with and without meconium ileus. The association between ΔF508 and CF mutations and restriction fragment length polymorphism haplotypes (XV2c and KM19) has been estimated; these data suggest that the CF chromosomes include a panel of independent and probably different mutations.     

Unraveling the complex genetic model for cystic fibrosis: pleiotropic effects of modifier genes on early cystic fibrosis-related morbidities

The existence of pleiotropy in disorders with multi-organ involvement can suggest therapeutic targets that could ameliorate overall disease severity. Here we assessed pleiotropy of modifier genes in cystic fibrosis (CF). CF, caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, affects the lungs, liver, pancreas and intestines. However, modifier genes contribute to variable disease severity across affected organs, even in individuals with the same CFTR genotype. We sought to determine whether SLC26A9, SLC9A3 and SLC6A14, that contribute to meconium ileus in CF, are pleiotropic for other early-affecting CF co-morbidities. In the Canadian CF population, we assessed evidence for pleiotropic effects on (1) pediatric lung disease severity (n = 815), (2) age at first acquisition of Pseudomonas aeruginosa (P. aeruginosa) (n = 730), and (3) prenatal pancreatic damage measured by immunoreactive trypsinogen (n = 126). A multiple-phenotype analytic strategy assessed evidence for pleiotropy in the presence of phenotypic correlation. We required the same alleles to be associated with detrimental effects. SLC26A9 was pleiotropic for meconium ileus and pancreatic damage (p = 0.002 at rs7512462), SLC9A3 for meconium ileus and lung disease (p = 1.5 × 10^?6 at rs17563161), and SLC6A14 for meconium ileus and both lung disease and age at first P. aeruginosa infection (p = 0.0002 and p = 0.006 at rs3788766, respectively). The meconium ileus risk alleles in SLC26A9, SLC9A3 and SLC6A14 are pleiotropic, increasing risk for other early CF co-morbidities. Furthermore, co-morbidities affecting the same organ tended to associate with the same genes. The existence of pleiotropy within this single disorder suggests that complementary therapeutic strategies to augment solute transport will benefit multiple CF-associated tissues.     

A large deletion causes apparent homozygosity for the D1152H mutation in the cystic fibrosis transmembrane regulator (CFTR) gene

We report the case of a patient with an apparent homozygosity for the D1152H mutation located in exon 18 of the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The parents had no personal history of cystic fibrosis (CF) and referred to our laboratory after the diagnosis of fetal bowel hyperechogenicity. The proband presented with meconium ileus and normal sweat chloride test. Sequencing of the CFTR exon 18 together with quantitative genomic assays, such as real-time PCR and the multiplex ligation probe amplification (MLPA) techniques, were performed and revealed that the father was heterozygous for the D1152H mutation and the mother carried a large deletion of the CFTR gene encompassing the genomic sequence including the same mutation. The child inherited D1152H from his father and the large deletion of the CFTR gene from his mother. We suggest that D1152H likely acts as a mild mutation with a dominant effect on the severe deletion of exon 18, considering that after 3 years of clinical examinations the child shows no classical signs and symptoms of CF. Not testing for large deletions in subjects with apparent homozygosity for a mutated CFTR allele could lead to the misidentification of CFTR mutation carrier status.     

Demographic and social characteristics of adults with cystic fibrosis in the United Kingdom.

OBJECTIVE--To obtain information about social and demographic characteristics and lifestyle of adult patients with cystic fibrosis, including those who do not attend major specialist clinics. DESIGN--Confidential self completion postal questionnaire to adult patients with cystic fibrosis, asking about social and demographic characteristics, social class and occupation, employment, education, insurance and social security benefits, symptom severity, and medical care. SETTING--National association for adults with cystic fibrosis. SUBJECTS--1052 adult members of the Association of Cystic Fibrosis Adults UK, accounting for 68% of those with cystic fibrosis in the United Kingdom population over 16 years of age and over 80% of those over 25 in June 1990. RESULTS--The response rate was 82% (397 women, 423 men). Most adults with cystic fibrosis were found to be living fulfilling lives into adulthood. Significantly fewer men were married or cohabiting than women (110 (26%) men, 175 (44%) women). 420 (55%) responders were working, and of these 235 (56%) had less than two weeks'' sick leave a year. Half of those not employed gave ill health as the reason. Revealing that they had cystic fibrosis at job interviews reduced likelihood of being employed for those with mild to moderate disease. People with cystic fibrosis had been less successful than the general population in achieving O level or equivalent qualifications, but more successful in achieving A level or higher qualifications. Achievement of any qualifications enhanced employment prospects irrespective of disease severity. CONCLUSION--Contrary to an image of chronic ill health and disability, a high proportion of adults with cystic fibrosis are living full and productive lives.     

Haplotypes associated with the cystic fibrosis gene (CF)

The linkage relationships between the cystic fibrosis locus and six marker loci allowed us to build 122 haplotypes bearing the CF gene and to compare them to the 122 normal haplotypes. We obtained 13 different marker haplotypes associated with the CF chromosomes and 22 with the normals in our population. To examine the possibility of a correlation between the clinical and the genetical polymorphism of the disease haplotype analysis was carried out taking in account age at diagnosis, severity of the disease and a particular clinical subgroup such as meconium ileus or pancreatic sufficiency. The results showed that a particular haplotype (121) is predominant in the severe form of the disease. This may have implication in diagnosis and prognosis of the disease.     

Meconium ileus caused by mutations in GUCY2C, encoding the CFTR-activating guanylate cyclase 2C

Meconium ileus, intestinal obstruction in the newborn, is caused in most cases by CFTR mutations modulated by yet-unidentified modifier genes. We now show that in two unrelated consanguineous Bedouin kindreds, an autosomal-recessive phenotype of meconium ileus that is not associated with cystic fibrosis (CF) is caused by different homozygous mutations in GUCY2C, leading to a dramatic reduction or fully abrogating the enzymatic activity of the encoded guanlyl cyclase 2C. GUCY2C is a transmembrane receptor whose extracellular domain is activated by either the endogenous ligands, guanylin and related peptide uroguanylin, or by an external ligand, Escherichia coli (E. coli) heat-stable enterotoxin STa. GUCY2C is expressed in the human intestine, and the encoded protein activates the CFTR protein through local generation of cGMP. Thus, GUCY2C is a likely candidate modifier of the meconium ileus phenotype in CF. Because GUCY2C heterozygous and homozygous mutant mice are resistant to E. coli STa enterotoxin-induced diarrhea, it is plausible that GUCY2C mutations in the desert-dwelling Bedouin kindred are of selective advantage.     

Sweat tests to diagnose cystic fibrosis in adults.

Twenty five patients with cystic fibrosis and 25 controls were studied to define a sweat sodium concentration in adults that could be taken as diagnostic of cystic fibrosis. Some of the controls had a sweat sodium concentration of over 50 mmol(mEq)/l, and thus cystic fibrosis should be diagnosed in an adult only when two measurements of sweat sodium concentration are above 70 mmol/l. In cases in which the sweat sodium concentration was borderline a suppression test using fludrocortisone improved the accuracy of diagnosis; this test entails recording the lowest concentration reached after administration of the drug. A scatter diagram of the baseline sweat sodium concentrations plotted against the lowest concentration attained after suppression with fludrocortisone may aid the diagnosis further.